diff options
Diffstat (limited to 'src/image/jpeg')
| -rw-r--r-- | src/image/jpeg/dct_test.go | 299 | ||||
| -rw-r--r-- | src/image/jpeg/fdct.go | 192 | ||||
| -rw-r--r-- | src/image/jpeg/huffman.go | 247 | ||||
| -rw-r--r-- | src/image/jpeg/idct.go | 194 | ||||
| -rw-r--r-- | src/image/jpeg/reader.go | 815 | ||||
| -rw-r--r-- | src/image/jpeg/reader_test.go | 517 | ||||
| -rw-r--r-- | src/image/jpeg/scan.go | 523 | ||||
| -rw-r--r-- | src/image/jpeg/writer.go | 641 | ||||
| -rw-r--r-- | src/image/jpeg/writer_test.go | 288 |
9 files changed, 3716 insertions, 0 deletions
diff --git a/src/image/jpeg/dct_test.go b/src/image/jpeg/dct_test.go new file mode 100644 index 0000000..845e758 --- /dev/null +++ b/src/image/jpeg/dct_test.go @@ -0,0 +1,299 @@ +// Copyright 2012 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package jpeg + +import ( + "bytes" + "fmt" + "math" + "math/rand" + "testing" +) + +func benchmarkDCT(b *testing.B, f func(*block)) { + b.StopTimer() + blocks := make([]block, 0, b.N*len(testBlocks)) + for i := 0; i < b.N; i++ { + blocks = append(blocks, testBlocks[:]...) + } + b.StartTimer() + for i := range blocks { + f(&blocks[i]) + } +} + +func BenchmarkFDCT(b *testing.B) { + benchmarkDCT(b, fdct) +} + +func BenchmarkIDCT(b *testing.B) { + benchmarkDCT(b, idct) +} + +func TestDCT(t *testing.T) { + blocks := make([]block, len(testBlocks)) + copy(blocks, testBlocks[:]) + + // Append some randomly generated blocks of varying sparseness. + r := rand.New(rand.NewSource(123)) + for i := 0; i < 100; i++ { + b := block{} + n := r.Int() % 64 + for j := 0; j < n; j++ { + b[r.Int()%len(b)] = r.Int31() % 256 + } + blocks = append(blocks, b) + } + + // Check that the FDCT and IDCT functions are inverses, after a scale and + // level shift. Scaling reduces the rounding errors in the conversion from + // floats to ints. + for i, b := range blocks { + got, want := b, b + for j := range got { + got[j] = (got[j] - 128) * 8 + } + slowFDCT(&got) + slowIDCT(&got) + for j := range got { + got[j] = got[j]/8 + 128 + } + if differ(&got, &want) { + t.Errorf("i=%d: IDCT(FDCT)\nsrc\n%s\ngot\n%s\nwant\n%s\n", i, &b, &got, &want) + } + } + + // Check that the optimized and slow FDCT implementations agree. + // The fdct function already does a scale and level shift. + for i, b := range blocks { + got, want := b, b + fdct(&got) + for j := range want { + want[j] = (want[j] - 128) * 8 + } + slowFDCT(&want) + if differ(&got, &want) { + t.Errorf("i=%d: FDCT\nsrc\n%s\ngot\n%s\nwant\n%s\n", i, &b, &got, &want) + } + } + + // Check that the optimized and slow IDCT implementations agree. + for i, b := range blocks { + got, want := b, b + idct(&got) + slowIDCT(&want) + if differ(&got, &want) { + t.Errorf("i=%d: IDCT\nsrc\n%s\ngot\n%s\nwant\n%s\n", i, &b, &got, &want) + } + } +} + +// differ reports whether any pair-wise elements in b0 and b1 differ by 2 or +// more. That tolerance is because there isn't a single definitive decoding of +// a given JPEG image, even before the YCbCr to RGB conversion; implementations +// can have different IDCT rounding errors. +func differ(b0, b1 *block) bool { + for i := range b0 { + delta := b0[i] - b1[i] + if delta < -2 || +2 < delta { + return true + } + } + return false +} + +// alpha returns 1 if i is 0 and returns √2 otherwise. +func alpha(i int) float64 { + if i == 0 { + return 1 + } + return math.Sqrt2 +} + +var cosines [32]float64 // cosines[k] = cos(π/2 * k/8) + +func init() { + for k := range cosines { + cosines[k] = math.Cos(math.Pi * float64(k) / 16) + } +} + +// slowFDCT performs the 8*8 2-dimensional forward discrete cosine transform: +// +// dst[u,v] = (1/8) * Σ_x Σ_y alpha(u) * alpha(v) * src[x,y] * +// cos((π/2) * (2*x + 1) * u / 8) * +// cos((π/2) * (2*y + 1) * v / 8) +// +// x and y are in pixel space, and u and v are in transform space. +// +// b acts as both dst and src. +func slowFDCT(b *block) { + var dst [blockSize]float64 + for v := 0; v < 8; v++ { + for u := 0; u < 8; u++ { + sum := 0.0 + for y := 0; y < 8; y++ { + for x := 0; x < 8; x++ { + sum += alpha(u) * alpha(v) * float64(b[8*y+x]) * + cosines[((2*x+1)*u)%32] * + cosines[((2*y+1)*v)%32] + } + } + dst[8*v+u] = sum / 8 + } + } + // Convert from float64 to int32. + for i := range dst { + b[i] = int32(dst[i] + 0.5) + } +} + +// slowIDCT performs the 8*8 2-dimensional inverse discrete cosine transform: +// +// dst[x,y] = (1/8) * Σ_u Σ_v alpha(u) * alpha(v) * src[u,v] * +// cos((π/2) * (2*x + 1) * u / 8) * +// cos((π/2) * (2*y + 1) * v / 8) +// +// x and y are in pixel space, and u and v are in transform space. +// +// b acts as both dst and src. +func slowIDCT(b *block) { + var dst [blockSize]float64 + for y := 0; y < 8; y++ { + for x := 0; x < 8; x++ { + sum := 0.0 + for v := 0; v < 8; v++ { + for u := 0; u < 8; u++ { + sum += alpha(u) * alpha(v) * float64(b[8*v+u]) * + cosines[((2*x+1)*u)%32] * + cosines[((2*y+1)*v)%32] + } + } + dst[8*y+x] = sum / 8 + } + } + // Convert from float64 to int32. + for i := range dst { + b[i] = int32(dst[i] + 0.5) + } +} + +func (b *block) String() string { + s := bytes.NewBuffer(nil) + fmt.Fprintf(s, "{\n") + for y := 0; y < 8; y++ { + fmt.Fprintf(s, "\t") + for x := 0; x < 8; x++ { + fmt.Fprintf(s, "0x%04x, ", uint16(b[8*y+x])) + } + fmt.Fprintln(s) + } + fmt.Fprintf(s, "}") + return s.String() +} + +// testBlocks are the first 10 pre-IDCT blocks from ../testdata/video-001.jpeg. +var testBlocks = [10]block{ + { + 0x7f, 0xf6, 0x01, 0x07, 0xff, 0x00, 0x00, 0x00, + 0xf5, 0x01, 0xfa, 0x01, 0xfe, 0x00, 0x01, 0x00, + 0x05, 0x05, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, + 0x01, 0xff, 0xf8, 0x00, 0x01, 0xff, 0x00, 0x00, + 0x00, 0x01, 0x00, 0x01, 0x00, 0xff, 0xff, 0x00, + 0xff, 0x0c, 0x00, 0x00, 0x00, 0x00, 0xff, 0x01, + 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, + 0x01, 0x00, 0x00, 0x01, 0xff, 0x01, 0x00, 0xfe, + }, + { + 0x29, 0x07, 0x00, 0xfc, 0x01, 0x01, 0x00, 0x00, + 0x07, 0x00, 0x03, 0x00, 0x01, 0x00, 0xff, 0xff, + 0xff, 0xfd, 0xff, 0x00, 0x00, 0x00, 0x00, 0x00, + 0x00, 0x00, 0x04, 0x00, 0xff, 0x01, 0x00, 0x00, + 0x01, 0x00, 0x01, 0xff, 0x00, 0x00, 0x00, 0x00, + 0x01, 0xfa, 0x01, 0x00, 0x01, 0x00, 0x01, 0xff, + 0x00, 0x00, 0xff, 0x00, 0x00, 0x00, 0x00, 0x00, + 0x00, 0x00, 0x00, 0xff, 0x00, 0xff, 0x00, 0x02, + }, + { + 0xc5, 0xfa, 0x01, 0x00, 0x00, 0x01, 0x00, 0xff, + 0x02, 0xff, 0x01, 0x00, 0x01, 0x00, 0xff, 0x00, + 0xff, 0xff, 0x00, 0xff, 0x01, 0x00, 0x00, 0x00, + 0xff, 0x00, 0x01, 0x00, 0x00, 0x00, 0xff, 0x00, + 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xff, + 0x00, 0xff, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, + 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, + 0xff, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, + }, + { + 0x86, 0x05, 0x00, 0x02, 0x00, 0x00, 0x01, 0x00, + 0xf2, 0x06, 0x00, 0x00, 0x01, 0x02, 0x00, 0x00, + 0xf6, 0xfa, 0xf9, 0x00, 0xff, 0x01, 0x00, 0x00, + 0xf9, 0x00, 0x00, 0xff, 0x00, 0x00, 0x00, 0x00, + 0x00, 0xff, 0x00, 0xff, 0xff, 0xff, 0x00, 0x00, + 0xff, 0x00, 0x00, 0x01, 0x00, 0xff, 0x01, 0x00, + 0x00, 0x00, 0x00, 0xff, 0x00, 0x00, 0x00, 0x01, + 0x00, 0x01, 0xff, 0x01, 0x00, 0xff, 0x00, 0x00, + }, + { + 0x24, 0xfe, 0x00, 0xff, 0x00, 0xff, 0xff, 0x00, + 0x08, 0xfd, 0x00, 0x01, 0x01, 0x00, 0x01, 0x00, + 0x06, 0x03, 0x03, 0xff, 0x00, 0x00, 0x00, 0x00, + 0x04, 0xff, 0x00, 0x00, 0x00, 0x00, 0x00, 0xff, + 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x01, + 0x01, 0x00, 0x01, 0xff, 0x00, 0x01, 0x00, 0x00, + 0x01, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, + 0x01, 0x00, 0x01, 0x00, 0x00, 0x00, 0xff, 0x01, + }, + { + 0xcd, 0xff, 0x00, 0x00, 0x00, 0x00, 0x01, 0x01, + 0x03, 0xff, 0x00, 0x00, 0x00, 0x00, 0x00, 0xff, + 0x01, 0x01, 0x01, 0x01, 0x01, 0x00, 0x00, 0x00, + 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, + 0x01, 0x00, 0x00, 0x00, 0x00, 0x01, 0x01, 0x00, + 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, + 0x00, 0xff, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, + 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0xff, + }, + { + 0x81, 0xfe, 0x05, 0xff, 0x01, 0xff, 0x01, 0x00, + 0xef, 0xf9, 0x00, 0xf9, 0x00, 0xff, 0x00, 0xff, + 0x05, 0xf9, 0x00, 0xf8, 0x01, 0xff, 0x01, 0xff, + 0x00, 0xff, 0x07, 0x00, 0x01, 0x00, 0x00, 0x00, + 0x01, 0x00, 0x01, 0x01, 0x00, 0x00, 0x00, 0x00, + 0x01, 0x00, 0x00, 0x00, 0xff, 0xff, 0x00, 0x01, + 0xff, 0x01, 0x01, 0x00, 0xff, 0x00, 0x00, 0x00, + 0x01, 0x01, 0x00, 0xff, 0x00, 0x00, 0x00, 0xff, + }, + { + 0x28, 0x00, 0xfe, 0x00, 0x00, 0x00, 0x00, 0x00, + 0x0b, 0x02, 0x01, 0x03, 0x00, 0xff, 0x00, 0x01, + 0xfe, 0x02, 0x01, 0x03, 0xff, 0x00, 0x00, 0x00, + 0x01, 0x00, 0xfd, 0x00, 0x01, 0x00, 0xff, 0x00, + 0x01, 0xff, 0x00, 0xff, 0x01, 0x00, 0x00, 0x00, + 0x00, 0x00, 0x00, 0xff, 0x01, 0x01, 0x00, 0xff, + 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, + 0xff, 0xff, 0x00, 0x00, 0x00, 0xff, 0x00, 0x01, + }, + { + 0xdf, 0xf9, 0xfe, 0x00, 0x03, 0x01, 0xff, 0xff, + 0x04, 0x01, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, + 0xff, 0x01, 0x01, 0x01, 0x00, 0x00, 0x00, 0x01, + 0x00, 0x00, 0xfe, 0x01, 0x00, 0x00, 0x00, 0x00, + 0x00, 0x00, 0xff, 0x01, 0x00, 0x00, 0x00, 0x01, + 0xff, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, + 0x00, 0xff, 0x00, 0xff, 0x01, 0x00, 0x00, 0x01, + 0xff, 0xff, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, + }, + { + 0x88, 0xfd, 0x00, 0x00, 0xff, 0x00, 0x01, 0xff, + 0xe1, 0x06, 0x06, 0x01, 0xff, 0x00, 0x01, 0x00, + 0x08, 0x00, 0xfa, 0x00, 0xff, 0xff, 0xff, 0xff, + 0x08, 0x01, 0x00, 0xff, 0x01, 0xff, 0x00, 0x00, + 0xf5, 0xff, 0x00, 0x01, 0xff, 0x01, 0x01, 0x00, + 0xff, 0xff, 0x01, 0xff, 0x01, 0x00, 0x01, 0x00, + 0x00, 0x01, 0x01, 0xff, 0x00, 0xff, 0x00, 0x01, + 0x02, 0x00, 0x00, 0xff, 0xff, 0x00, 0xff, 0x00, + }, +} diff --git a/src/image/jpeg/fdct.go b/src/image/jpeg/fdct.go new file mode 100644 index 0000000..c7a973e --- /dev/null +++ b/src/image/jpeg/fdct.go @@ -0,0 +1,192 @@ +// Copyright 2011 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package jpeg + +// This file implements a Forward Discrete Cosine Transformation. + +/* +It is based on the code in jfdctint.c from the Independent JPEG Group, +found at http://www.ijg.org/files/jpegsrc.v8c.tar.gz. + +The "LEGAL ISSUES" section of the README in that archive says: + +In plain English: + +1. We don't promise that this software works. (But if you find any bugs, + please let us know!) +2. You can use this software for whatever you want. You don't have to pay us. +3. You may not pretend that you wrote this software. If you use it in a + program, you must acknowledge somewhere in your documentation that + you've used the IJG code. + +In legalese: + +The authors make NO WARRANTY or representation, either express or implied, +with respect to this software, its quality, accuracy, merchantability, or +fitness for a particular purpose. This software is provided "AS IS", and you, +its user, assume the entire risk as to its quality and accuracy. + +This software is copyright (C) 1991-2011, Thomas G. Lane, Guido Vollbeding. +All Rights Reserved except as specified below. + +Permission is hereby granted to use, copy, modify, and distribute this +software (or portions thereof) for any purpose, without fee, subject to these +conditions: +(1) If any part of the source code for this software is distributed, then this +README file must be included, with this copyright and no-warranty notice +unaltered; and any additions, deletions, or changes to the original files +must be clearly indicated in accompanying documentation. +(2) If only executable code is distributed, then the accompanying +documentation must state that "this software is based in part on the work of +the Independent JPEG Group". +(3) Permission for use of this software is granted only if the user accepts +full responsibility for any undesirable consequences; the authors accept +NO LIABILITY for damages of any kind. + +These conditions apply to any software derived from or based on the IJG code, +not just to the unmodified library. If you use our work, you ought to +acknowledge us. + +Permission is NOT granted for the use of any IJG author's name or company name +in advertising or publicity relating to this software or products derived from +it. This software may be referred to only as "the Independent JPEG Group's +software". + +We specifically permit and encourage the use of this software as the basis of +commercial products, provided that all warranty or liability claims are +assumed by the product vendor. +*/ + +// Trigonometric constants in 13-bit fixed point format. +const ( + fix_0_298631336 = 2446 + fix_0_390180644 = 3196 + fix_0_541196100 = 4433 + fix_0_765366865 = 6270 + fix_0_899976223 = 7373 + fix_1_175875602 = 9633 + fix_1_501321110 = 12299 + fix_1_847759065 = 15137 + fix_1_961570560 = 16069 + fix_2_053119869 = 16819 + fix_2_562915447 = 20995 + fix_3_072711026 = 25172 +) + +const ( + constBits = 13 + pass1Bits = 2 + centerJSample = 128 +) + +// fdct performs a forward DCT on an 8x8 block of coefficients, including a +// level shift. +func fdct(b *block) { + // Pass 1: process rows. + for y := 0; y < 8; y++ { + y8 := y * 8 + s := b[y8 : y8+8 : y8+8] // Small cap improves performance, see https://golang.org/issue/27857 + x0 := s[0] + x1 := s[1] + x2 := s[2] + x3 := s[3] + x4 := s[4] + x5 := s[5] + x6 := s[6] + x7 := s[7] + + tmp0 := x0 + x7 + tmp1 := x1 + x6 + tmp2 := x2 + x5 + tmp3 := x3 + x4 + + tmp10 := tmp0 + tmp3 + tmp12 := tmp0 - tmp3 + tmp11 := tmp1 + tmp2 + tmp13 := tmp1 - tmp2 + + tmp0 = x0 - x7 + tmp1 = x1 - x6 + tmp2 = x2 - x5 + tmp3 = x3 - x4 + + s[0] = (tmp10 + tmp11 - 8*centerJSample) << pass1Bits + s[4] = (tmp10 - tmp11) << pass1Bits + z1 := (tmp12 + tmp13) * fix_0_541196100 + z1 += 1 << (constBits - pass1Bits - 1) + s[2] = (z1 + tmp12*fix_0_765366865) >> (constBits - pass1Bits) + s[6] = (z1 - tmp13*fix_1_847759065) >> (constBits - pass1Bits) + + tmp10 = tmp0 + tmp3 + tmp11 = tmp1 + tmp2 + tmp12 = tmp0 + tmp2 + tmp13 = tmp1 + tmp3 + z1 = (tmp12 + tmp13) * fix_1_175875602 + z1 += 1 << (constBits - pass1Bits - 1) + tmp0 *= fix_1_501321110 + tmp1 *= fix_3_072711026 + tmp2 *= fix_2_053119869 + tmp3 *= fix_0_298631336 + tmp10 *= -fix_0_899976223 + tmp11 *= -fix_2_562915447 + tmp12 *= -fix_0_390180644 + tmp13 *= -fix_1_961570560 + + tmp12 += z1 + tmp13 += z1 + s[1] = (tmp0 + tmp10 + tmp12) >> (constBits - pass1Bits) + s[3] = (tmp1 + tmp11 + tmp13) >> (constBits - pass1Bits) + s[5] = (tmp2 + tmp11 + tmp12) >> (constBits - pass1Bits) + s[7] = (tmp3 + tmp10 + tmp13) >> (constBits - pass1Bits) + } + // Pass 2: process columns. + // We remove pass1Bits scaling, but leave results scaled up by an overall factor of 8. + for x := 0; x < 8; x++ { + tmp0 := b[0*8+x] + b[7*8+x] + tmp1 := b[1*8+x] + b[6*8+x] + tmp2 := b[2*8+x] + b[5*8+x] + tmp3 := b[3*8+x] + b[4*8+x] + + tmp10 := tmp0 + tmp3 + 1<<(pass1Bits-1) + tmp12 := tmp0 - tmp3 + tmp11 := tmp1 + tmp2 + tmp13 := tmp1 - tmp2 + + tmp0 = b[0*8+x] - b[7*8+x] + tmp1 = b[1*8+x] - b[6*8+x] + tmp2 = b[2*8+x] - b[5*8+x] + tmp3 = b[3*8+x] - b[4*8+x] + + b[0*8+x] = (tmp10 + tmp11) >> pass1Bits + b[4*8+x] = (tmp10 - tmp11) >> pass1Bits + + z1 := (tmp12 + tmp13) * fix_0_541196100 + z1 += 1 << (constBits + pass1Bits - 1) + b[2*8+x] = (z1 + tmp12*fix_0_765366865) >> (constBits + pass1Bits) + b[6*8+x] = (z1 - tmp13*fix_1_847759065) >> (constBits + pass1Bits) + + tmp10 = tmp0 + tmp3 + tmp11 = tmp1 + tmp2 + tmp12 = tmp0 + tmp2 + tmp13 = tmp1 + tmp3 + z1 = (tmp12 + tmp13) * fix_1_175875602 + z1 += 1 << (constBits + pass1Bits - 1) + tmp0 *= fix_1_501321110 + tmp1 *= fix_3_072711026 + tmp2 *= fix_2_053119869 + tmp3 *= fix_0_298631336 + tmp10 *= -fix_0_899976223 + tmp11 *= -fix_2_562915447 + tmp12 *= -fix_0_390180644 + tmp13 *= -fix_1_961570560 + + tmp12 += z1 + tmp13 += z1 + b[1*8+x] = (tmp0 + tmp10 + tmp12) >> (constBits + pass1Bits) + b[3*8+x] = (tmp1 + tmp11 + tmp13) >> (constBits + pass1Bits) + b[5*8+x] = (tmp2 + tmp11 + tmp12) >> (constBits + pass1Bits) + b[7*8+x] = (tmp3 + tmp10 + tmp13) >> (constBits + pass1Bits) + } +} diff --git a/src/image/jpeg/huffman.go b/src/image/jpeg/huffman.go new file mode 100644 index 0000000..95aaf71 --- /dev/null +++ b/src/image/jpeg/huffman.go @@ -0,0 +1,247 @@ +// Copyright 2009 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package jpeg + +import ( + "io" +) + +// maxCodeLength is the maximum (inclusive) number of bits in a Huffman code. +const maxCodeLength = 16 + +// maxNCodes is the maximum (inclusive) number of codes in a Huffman tree. +const maxNCodes = 256 + +// lutSize is the log-2 size of the Huffman decoder's look-up table. +const lutSize = 8 + +// huffman is a Huffman decoder, specified in section C. +type huffman struct { + // length is the number of codes in the tree. + nCodes int32 + // lut is the look-up table for the next lutSize bits in the bit-stream. + // The high 8 bits of the uint16 are the encoded value. The low 8 bits + // are 1 plus the code length, or 0 if the value is too large to fit in + // lutSize bits. + lut [1 << lutSize]uint16 + // vals are the decoded values, sorted by their encoding. + vals [maxNCodes]uint8 + // minCodes[i] is the minimum code of length i, or -1 if there are no + // codes of that length. + minCodes [maxCodeLength]int32 + // maxCodes[i] is the maximum code of length i, or -1 if there are no + // codes of that length. + maxCodes [maxCodeLength]int32 + // valsIndices[i] is the index into vals of minCodes[i]. + valsIndices [maxCodeLength]int32 +} + +// errShortHuffmanData means that an unexpected EOF occurred while decoding +// Huffman data. +var errShortHuffmanData = FormatError("short Huffman data") + +// ensureNBits reads bytes from the byte buffer to ensure that d.bits.n is at +// least n. For best performance (avoiding function calls inside hot loops), +// the caller is the one responsible for first checking that d.bits.n < n. +func (d *decoder) ensureNBits(n int32) error { + for { + c, err := d.readByteStuffedByte() + if err != nil { + if err == io.EOF { + return errShortHuffmanData + } + return err + } + d.bits.a = d.bits.a<<8 | uint32(c) + d.bits.n += 8 + if d.bits.m == 0 { + d.bits.m = 1 << 7 + } else { + d.bits.m <<= 8 + } + if d.bits.n >= n { + break + } + } + return nil +} + +// receiveExtend is the composition of RECEIVE and EXTEND, specified in section +// F.2.2.1. +func (d *decoder) receiveExtend(t uint8) (int32, error) { + if d.bits.n < int32(t) { + if err := d.ensureNBits(int32(t)); err != nil { + return 0, err + } + } + d.bits.n -= int32(t) + d.bits.m >>= t + s := int32(1) << t + x := int32(d.bits.a>>uint8(d.bits.n)) & (s - 1) + if x < s>>1 { + x += ((-1) << t) + 1 + } + return x, nil +} + +// processDHT processes a Define Huffman Table marker, and initializes a huffman +// struct from its contents. Specified in section B.2.4.2. +func (d *decoder) processDHT(n int) error { + for n > 0 { + if n < 17 { + return FormatError("DHT has wrong length") + } + if err := d.readFull(d.tmp[:17]); err != nil { + return err + } + tc := d.tmp[0] >> 4 + if tc > maxTc { + return FormatError("bad Tc value") + } + th := d.tmp[0] & 0x0f + // The baseline th <= 1 restriction is specified in table B.5. + if th > maxTh || (d.baseline && th > 1) { + return FormatError("bad Th value") + } + h := &d.huff[tc][th] + + // Read nCodes and h.vals (and derive h.nCodes). + // nCodes[i] is the number of codes with code length i. + // h.nCodes is the total number of codes. + h.nCodes = 0 + var nCodes [maxCodeLength]int32 + for i := range nCodes { + nCodes[i] = int32(d.tmp[i+1]) + h.nCodes += nCodes[i] + } + if h.nCodes == 0 { + return FormatError("Huffman table has zero length") + } + if h.nCodes > maxNCodes { + return FormatError("Huffman table has excessive length") + } + n -= int(h.nCodes) + 17 + if n < 0 { + return FormatError("DHT has wrong length") + } + if err := d.readFull(h.vals[:h.nCodes]); err != nil { + return err + } + + // Derive the look-up table. + for i := range h.lut { + h.lut[i] = 0 + } + var x, code uint32 + for i := uint32(0); i < lutSize; i++ { + code <<= 1 + for j := int32(0); j < nCodes[i]; j++ { + // The codeLength is 1+i, so shift code by 8-(1+i) to + // calculate the high bits for every 8-bit sequence + // whose codeLength's high bits matches code. + // The high 8 bits of lutValue are the encoded value. + // The low 8 bits are 1 plus the codeLength. + base := uint8(code << (7 - i)) + lutValue := uint16(h.vals[x])<<8 | uint16(2+i) + for k := uint8(0); k < 1<<(7-i); k++ { + h.lut[base|k] = lutValue + } + code++ + x++ + } + } + + // Derive minCodes, maxCodes, and valsIndices. + var c, index int32 + for i, n := range nCodes { + if n == 0 { + h.minCodes[i] = -1 + h.maxCodes[i] = -1 + h.valsIndices[i] = -1 + } else { + h.minCodes[i] = c + h.maxCodes[i] = c + n - 1 + h.valsIndices[i] = index + c += n + index += n + } + c <<= 1 + } + } + return nil +} + +// decodeHuffman returns the next Huffman-coded value from the bit-stream, +// decoded according to h. +func (d *decoder) decodeHuffman(h *huffman) (uint8, error) { + if h.nCodes == 0 { + return 0, FormatError("uninitialized Huffman table") + } + + if d.bits.n < 8 { + if err := d.ensureNBits(8); err != nil { + if err != errMissingFF00 && err != errShortHuffmanData { + return 0, err + } + // There are no more bytes of data in this segment, but we may still + // be able to read the next symbol out of the previously read bits. + // First, undo the readByte that the ensureNBits call made. + if d.bytes.nUnreadable != 0 { + d.unreadByteStuffedByte() + } + goto slowPath + } + } + if v := h.lut[(d.bits.a>>uint32(d.bits.n-lutSize))&0xff]; v != 0 { + n := (v & 0xff) - 1 + d.bits.n -= int32(n) + d.bits.m >>= n + return uint8(v >> 8), nil + } + +slowPath: + for i, code := 0, int32(0); i < maxCodeLength; i++ { + if d.bits.n == 0 { + if err := d.ensureNBits(1); err != nil { + return 0, err + } + } + if d.bits.a&d.bits.m != 0 { + code |= 1 + } + d.bits.n-- + d.bits.m >>= 1 + if code <= h.maxCodes[i] { + return h.vals[h.valsIndices[i]+code-h.minCodes[i]], nil + } + code <<= 1 + } + return 0, FormatError("bad Huffman code") +} + +func (d *decoder) decodeBit() (bool, error) { + if d.bits.n == 0 { + if err := d.ensureNBits(1); err != nil { + return false, err + } + } + ret := d.bits.a&d.bits.m != 0 + d.bits.n-- + d.bits.m >>= 1 + return ret, nil +} + +func (d *decoder) decodeBits(n int32) (uint32, error) { + if d.bits.n < n { + if err := d.ensureNBits(n); err != nil { + return 0, err + } + } + ret := d.bits.a >> uint32(d.bits.n-n) + ret &= (1 << uint32(n)) - 1 + d.bits.n -= n + d.bits.m >>= uint32(n) + return ret, nil +} diff --git a/src/image/jpeg/idct.go b/src/image/jpeg/idct.go new file mode 100644 index 0000000..a3957c8 --- /dev/null +++ b/src/image/jpeg/idct.go @@ -0,0 +1,194 @@ +// Copyright 2009 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package jpeg + +// This is a Go translation of idct.c from +// +// http://standards.iso.org/ittf/PubliclyAvailableStandards/ISO_IEC_13818-4_2004_Conformance_Testing/Video/verifier/mpeg2decode_960109.tar.gz +// +// which carries the following notice: + +/* Copyright (C) 1996, MPEG Software Simulation Group. All Rights Reserved. */ + +/* + * Disclaimer of Warranty + * + * These software programs are available to the user without any license fee or + * royalty on an "as is" basis. The MPEG Software Simulation Group disclaims + * any and all warranties, whether express, implied, or statuary, including any + * implied warranties or merchantability or of fitness for a particular + * purpose. In no event shall the copyright-holder be liable for any + * incidental, punitive, or consequential damages of any kind whatsoever + * arising from the use of these programs. + * + * This disclaimer of warranty extends to the user of these programs and user's + * customers, employees, agents, transferees, successors, and assigns. + * + * The MPEG Software Simulation Group does not represent or warrant that the + * programs furnished hereunder are free of infringement of any third-party + * patents. + * + * Commercial implementations of MPEG-1 and MPEG-2 video, including shareware, + * are subject to royalty fees to patent holders. Many of these patents are + * general enough such that they are unavoidable regardless of implementation + * design. + * + */ + +const blockSize = 64 // A DCT block is 8x8. + +type block [blockSize]int32 + +const ( + w1 = 2841 // 2048*sqrt(2)*cos(1*pi/16) + w2 = 2676 // 2048*sqrt(2)*cos(2*pi/16) + w3 = 2408 // 2048*sqrt(2)*cos(3*pi/16) + w5 = 1609 // 2048*sqrt(2)*cos(5*pi/16) + w6 = 1108 // 2048*sqrt(2)*cos(6*pi/16) + w7 = 565 // 2048*sqrt(2)*cos(7*pi/16) + + w1pw7 = w1 + w7 + w1mw7 = w1 - w7 + w2pw6 = w2 + w6 + w2mw6 = w2 - w6 + w3pw5 = w3 + w5 + w3mw5 = w3 - w5 + + r2 = 181 // 256/sqrt(2) +) + +// idct performs a 2-D Inverse Discrete Cosine Transformation. +// +// The input coefficients should already have been multiplied by the +// appropriate quantization table. We use fixed-point computation, with the +// number of bits for the fractional component varying over the intermediate +// stages. +// +// For more on the actual algorithm, see Z. Wang, "Fast algorithms for the +// discrete W transform and for the discrete Fourier transform", IEEE Trans. on +// ASSP, Vol. ASSP- 32, pp. 803-816, Aug. 1984. +func idct(src *block) { + // Horizontal 1-D IDCT. + for y := 0; y < 8; y++ { + y8 := y * 8 + s := src[y8 : y8+8 : y8+8] // Small cap improves performance, see https://golang.org/issue/27857 + // If all the AC components are zero, then the IDCT is trivial. + if s[1] == 0 && s[2] == 0 && s[3] == 0 && + s[4] == 0 && s[5] == 0 && s[6] == 0 && s[7] == 0 { + dc := s[0] << 3 + s[0] = dc + s[1] = dc + s[2] = dc + s[3] = dc + s[4] = dc + s[5] = dc + s[6] = dc + s[7] = dc + continue + } + + // Prescale. + x0 := (s[0] << 11) + 128 + x1 := s[4] << 11 + x2 := s[6] + x3 := s[2] + x4 := s[1] + x5 := s[7] + x6 := s[5] + x7 := s[3] + + // Stage 1. + x8 := w7 * (x4 + x5) + x4 = x8 + w1mw7*x4 + x5 = x8 - w1pw7*x5 + x8 = w3 * (x6 + x7) + x6 = x8 - w3mw5*x6 + x7 = x8 - w3pw5*x7 + + // Stage 2. + x8 = x0 + x1 + x0 -= x1 + x1 = w6 * (x3 + x2) + x2 = x1 - w2pw6*x2 + x3 = x1 + w2mw6*x3 + x1 = x4 + x6 + x4 -= x6 + x6 = x5 + x7 + x5 -= x7 + + // Stage 3. + x7 = x8 + x3 + x8 -= x3 + x3 = x0 + x2 + x0 -= x2 + x2 = (r2*(x4+x5) + 128) >> 8 + x4 = (r2*(x4-x5) + 128) >> 8 + + // Stage 4. + s[0] = (x7 + x1) >> 8 + s[1] = (x3 + x2) >> 8 + s[2] = (x0 + x4) >> 8 + s[3] = (x8 + x6) >> 8 + s[4] = (x8 - x6) >> 8 + s[5] = (x0 - x4) >> 8 + s[6] = (x3 - x2) >> 8 + s[7] = (x7 - x1) >> 8 + } + + // Vertical 1-D IDCT. + for x := 0; x < 8; x++ { + // Similar to the horizontal 1-D IDCT case, if all the AC components are zero, then the IDCT is trivial. + // However, after performing the horizontal 1-D IDCT, there are typically non-zero AC components, so + // we do not bother to check for the all-zero case. + s := src[x : x+57 : x+57] // Small cap improves performance, see https://golang.org/issue/27857 + + // Prescale. + y0 := (s[8*0] << 8) + 8192 + y1 := s[8*4] << 8 + y2 := s[8*6] + y3 := s[8*2] + y4 := s[8*1] + y5 := s[8*7] + y6 := s[8*5] + y7 := s[8*3] + + // Stage 1. + y8 := w7*(y4+y5) + 4 + y4 = (y8 + w1mw7*y4) >> 3 + y5 = (y8 - w1pw7*y5) >> 3 + y8 = w3*(y6+y7) + 4 + y6 = (y8 - w3mw5*y6) >> 3 + y7 = (y8 - w3pw5*y7) >> 3 + + // Stage 2. + y8 = y0 + y1 + y0 -= y1 + y1 = w6*(y3+y2) + 4 + y2 = (y1 - w2pw6*y2) >> 3 + y3 = (y1 + w2mw6*y3) >> 3 + y1 = y4 + y6 + y4 -= y6 + y6 = y5 + y7 + y5 -= y7 + + // Stage 3. + y7 = y8 + y3 + y8 -= y3 + y3 = y0 + y2 + y0 -= y2 + y2 = (r2*(y4+y5) + 128) >> 8 + y4 = (r2*(y4-y5) + 128) >> 8 + + // Stage 4. + s[8*0] = (y7 + y1) >> 14 + s[8*1] = (y3 + y2) >> 14 + s[8*2] = (y0 + y4) >> 14 + s[8*3] = (y8 + y6) >> 14 + s[8*4] = (y8 - y6) >> 14 + s[8*5] = (y0 - y4) >> 14 + s[8*6] = (y3 - y2) >> 14 + s[8*7] = (y7 - y1) >> 14 + } +} diff --git a/src/image/jpeg/reader.go b/src/image/jpeg/reader.go new file mode 100644 index 0000000..b340723 --- /dev/null +++ b/src/image/jpeg/reader.go @@ -0,0 +1,815 @@ +// Copyright 2009 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +// Package jpeg implements a JPEG image decoder and encoder. +// +// JPEG is defined in ITU-T T.81: https://www.w3.org/Graphics/JPEG/itu-t81.pdf. +package jpeg + +import ( + "image" + "image/color" + "image/internal/imageutil" + "io" +) + +// A FormatError reports that the input is not a valid JPEG. +type FormatError string + +func (e FormatError) Error() string { return "invalid JPEG format: " + string(e) } + +// An UnsupportedError reports that the input uses a valid but unimplemented JPEG feature. +type UnsupportedError string + +func (e UnsupportedError) Error() string { return "unsupported JPEG feature: " + string(e) } + +var errUnsupportedSubsamplingRatio = UnsupportedError("luma/chroma subsampling ratio") + +// Component specification, specified in section B.2.2. +type component struct { + h int // Horizontal sampling factor. + v int // Vertical sampling factor. + c uint8 // Component identifier. + tq uint8 // Quantization table destination selector. +} + +const ( + dcTable = 0 + acTable = 1 + maxTc = 1 + maxTh = 3 + maxTq = 3 + + maxComponents = 4 +) + +const ( + sof0Marker = 0xc0 // Start Of Frame (Baseline Sequential). + sof1Marker = 0xc1 // Start Of Frame (Extended Sequential). + sof2Marker = 0xc2 // Start Of Frame (Progressive). + dhtMarker = 0xc4 // Define Huffman Table. + rst0Marker = 0xd0 // ReSTart (0). + rst7Marker = 0xd7 // ReSTart (7). + soiMarker = 0xd8 // Start Of Image. + eoiMarker = 0xd9 // End Of Image. + sosMarker = 0xda // Start Of Scan. + dqtMarker = 0xdb // Define Quantization Table. + driMarker = 0xdd // Define Restart Interval. + comMarker = 0xfe // COMment. + // "APPlication specific" markers aren't part of the JPEG spec per se, + // but in practice, their use is described at + // https://www.sno.phy.queensu.ca/~phil/exiftool/TagNames/JPEG.html + app0Marker = 0xe0 + app14Marker = 0xee + app15Marker = 0xef +) + +// See https://www.sno.phy.queensu.ca/~phil/exiftool/TagNames/JPEG.html#Adobe +const ( + adobeTransformUnknown = 0 + adobeTransformYCbCr = 1 + adobeTransformYCbCrK = 2 +) + +// unzig maps from the zig-zag ordering to the natural ordering. For example, +// unzig[3] is the column and row of the fourth element in zig-zag order. The +// value is 16, which means first column (16%8 == 0) and third row (16/8 == 2). +var unzig = [blockSize]int{ + 0, 1, 8, 16, 9, 2, 3, 10, + 17, 24, 32, 25, 18, 11, 4, 5, + 12, 19, 26, 33, 40, 48, 41, 34, + 27, 20, 13, 6, 7, 14, 21, 28, + 35, 42, 49, 56, 57, 50, 43, 36, + 29, 22, 15, 23, 30, 37, 44, 51, + 58, 59, 52, 45, 38, 31, 39, 46, + 53, 60, 61, 54, 47, 55, 62, 63, +} + +// Deprecated: Reader is not used by the image/jpeg package and should +// not be used by others. It is kept for compatibility. +type Reader interface { + io.ByteReader + io.Reader +} + +// bits holds the unprocessed bits that have been taken from the byte-stream. +// The n least significant bits of a form the unread bits, to be read in MSB to +// LSB order. +type bits struct { + a uint32 // accumulator. + m uint32 // mask. m==1<<(n-1) when n>0, with m==0 when n==0. + n int32 // the number of unread bits in a. +} + +type decoder struct { + r io.Reader + bits bits + // bytes is a byte buffer, similar to a bufio.Reader, except that it + // has to be able to unread more than 1 byte, due to byte stuffing. + // Byte stuffing is specified in section F.1.2.3. + bytes struct { + // buf[i:j] are the buffered bytes read from the underlying + // io.Reader that haven't yet been passed further on. + buf [4096]byte + i, j int + // nUnreadable is the number of bytes to back up i after + // overshooting. It can be 0, 1 or 2. + nUnreadable int + } + width, height int + + img1 *image.Gray + img3 *image.YCbCr + blackPix []byte + blackStride int + + ri int // Restart Interval. + nComp int + + // As per section 4.5, there are four modes of operation (selected by the + // SOF? markers): sequential DCT, progressive DCT, lossless and + // hierarchical, although this implementation does not support the latter + // two non-DCT modes. Sequential DCT is further split into baseline and + // extended, as per section 4.11. + baseline bool + progressive bool + + jfif bool + adobeTransformValid bool + adobeTransform uint8 + eobRun uint16 // End-of-Band run, specified in section G.1.2.2. + + comp [maxComponents]component + progCoeffs [maxComponents][]block // Saved state between progressive-mode scans. + huff [maxTc + 1][maxTh + 1]huffman + quant [maxTq + 1]block // Quantization tables, in zig-zag order. + tmp [2 * blockSize]byte +} + +// fill fills up the d.bytes.buf buffer from the underlying io.Reader. It +// should only be called when there are no unread bytes in d.bytes. +func (d *decoder) fill() error { + if d.bytes.i != d.bytes.j { + panic("jpeg: fill called when unread bytes exist") + } + // Move the last 2 bytes to the start of the buffer, in case we need + // to call unreadByteStuffedByte. + if d.bytes.j > 2 { + d.bytes.buf[0] = d.bytes.buf[d.bytes.j-2] + d.bytes.buf[1] = d.bytes.buf[d.bytes.j-1] + d.bytes.i, d.bytes.j = 2, 2 + } + // Fill in the rest of the buffer. + n, err := d.r.Read(d.bytes.buf[d.bytes.j:]) + d.bytes.j += n + if n > 0 { + err = nil + } + return err +} + +// unreadByteStuffedByte undoes the most recent readByteStuffedByte call, +// giving a byte of data back from d.bits to d.bytes. The Huffman look-up table +// requires at least 8 bits for look-up, which means that Huffman decoding can +// sometimes overshoot and read one or two too many bytes. Two-byte overshoot +// can happen when expecting to read a 0xff 0x00 byte-stuffed byte. +func (d *decoder) unreadByteStuffedByte() { + d.bytes.i -= d.bytes.nUnreadable + d.bytes.nUnreadable = 0 + if d.bits.n >= 8 { + d.bits.a >>= 8 + d.bits.n -= 8 + d.bits.m >>= 8 + } +} + +// readByte returns the next byte, whether buffered or not buffered. It does +// not care about byte stuffing. +func (d *decoder) readByte() (x byte, err error) { + for d.bytes.i == d.bytes.j { + if err = d.fill(); err != nil { + return 0, err + } + } + x = d.bytes.buf[d.bytes.i] + d.bytes.i++ + d.bytes.nUnreadable = 0 + return x, nil +} + +// errMissingFF00 means that readByteStuffedByte encountered an 0xff byte (a +// marker byte) that wasn't the expected byte-stuffed sequence 0xff, 0x00. +var errMissingFF00 = FormatError("missing 0xff00 sequence") + +// readByteStuffedByte is like readByte but is for byte-stuffed Huffman data. +func (d *decoder) readByteStuffedByte() (x byte, err error) { + // Take the fast path if d.bytes.buf contains at least two bytes. + if d.bytes.i+2 <= d.bytes.j { + x = d.bytes.buf[d.bytes.i] + d.bytes.i++ + d.bytes.nUnreadable = 1 + if x != 0xff { + return x, err + } + if d.bytes.buf[d.bytes.i] != 0x00 { + return 0, errMissingFF00 + } + d.bytes.i++ + d.bytes.nUnreadable = 2 + return 0xff, nil + } + + d.bytes.nUnreadable = 0 + + x, err = d.readByte() + if err != nil { + return 0, err + } + d.bytes.nUnreadable = 1 + if x != 0xff { + return x, nil + } + + x, err = d.readByte() + if err != nil { + return 0, err + } + d.bytes.nUnreadable = 2 + if x != 0x00 { + return 0, errMissingFF00 + } + return 0xff, nil +} + +// readFull reads exactly len(p) bytes into p. It does not care about byte +// stuffing. +func (d *decoder) readFull(p []byte) error { + // Unread the overshot bytes, if any. + if d.bytes.nUnreadable != 0 { + if d.bits.n >= 8 { + d.unreadByteStuffedByte() + } + d.bytes.nUnreadable = 0 + } + + for { + n := copy(p, d.bytes.buf[d.bytes.i:d.bytes.j]) + p = p[n:] + d.bytes.i += n + if len(p) == 0 { + break + } + if err := d.fill(); err != nil { + if err == io.EOF { + err = io.ErrUnexpectedEOF + } + return err + } + } + return nil +} + +// ignore ignores the next n bytes. +func (d *decoder) ignore(n int) error { + // Unread the overshot bytes, if any. + if d.bytes.nUnreadable != 0 { + if d.bits.n >= 8 { + d.unreadByteStuffedByte() + } + d.bytes.nUnreadable = 0 + } + + for { + m := d.bytes.j - d.bytes.i + if m > n { + m = n + } + d.bytes.i += m + n -= m + if n == 0 { + break + } + if err := d.fill(); err != nil { + if err == io.EOF { + err = io.ErrUnexpectedEOF + } + return err + } + } + return nil +} + +// Specified in section B.2.2. +func (d *decoder) processSOF(n int) error { + if d.nComp != 0 { + return FormatError("multiple SOF markers") + } + switch n { + case 6 + 3*1: // Grayscale image. + d.nComp = 1 + case 6 + 3*3: // YCbCr or RGB image. + d.nComp = 3 + case 6 + 3*4: // YCbCrK or CMYK image. + d.nComp = 4 + default: + return UnsupportedError("number of components") + } + if err := d.readFull(d.tmp[:n]); err != nil { + return err + } + // We only support 8-bit precision. + if d.tmp[0] != 8 { + return UnsupportedError("precision") + } + d.height = int(d.tmp[1])<<8 + int(d.tmp[2]) + d.width = int(d.tmp[3])<<8 + int(d.tmp[4]) + if int(d.tmp[5]) != d.nComp { + return FormatError("SOF has wrong length") + } + + for i := 0; i < d.nComp; i++ { + d.comp[i].c = d.tmp[6+3*i] + // Section B.2.2 states that "the value of C_i shall be different from + // the values of C_1 through C_(i-1)". + for j := 0; j < i; j++ { + if d.comp[i].c == d.comp[j].c { + return FormatError("repeated component identifier") + } + } + + d.comp[i].tq = d.tmp[8+3*i] + if d.comp[i].tq > maxTq { + return FormatError("bad Tq value") + } + + hv := d.tmp[7+3*i] + h, v := int(hv>>4), int(hv&0x0f) + if h < 1 || 4 < h || v < 1 || 4 < v { + return FormatError("luma/chroma subsampling ratio") + } + if h == 3 || v == 3 { + return errUnsupportedSubsamplingRatio + } + switch d.nComp { + case 1: + // If a JPEG image has only one component, section A.2 says "this data + // is non-interleaved by definition" and section A.2.2 says "[in this + // case...] the order of data units within a scan shall be left-to-right + // and top-to-bottom... regardless of the values of H_1 and V_1". Section + // 4.8.2 also says "[for non-interleaved data], the MCU is defined to be + // one data unit". Similarly, section A.1.1 explains that it is the ratio + // of H_i to max_j(H_j) that matters, and similarly for V. For grayscale + // images, H_1 is the maximum H_j for all components j, so that ratio is + // always 1. The component's (h, v) is effectively always (1, 1): even if + // the nominal (h, v) is (2, 1), a 20x5 image is encoded in three 8x8 + // MCUs, not two 16x8 MCUs. + h, v = 1, 1 + + case 3: + // For YCbCr images, we only support 4:4:4, 4:4:0, 4:2:2, 4:2:0, + // 4:1:1 or 4:1:0 chroma subsampling ratios. This implies that the + // (h, v) values for the Y component are either (1, 1), (1, 2), + // (2, 1), (2, 2), (4, 1) or (4, 2), and the Y component's values + // must be a multiple of the Cb and Cr component's values. We also + // assume that the two chroma components have the same subsampling + // ratio. + switch i { + case 0: // Y. + // We have already verified, above, that h and v are both + // either 1, 2 or 4, so invalid (h, v) combinations are those + // with v == 4. + if v == 4 { + return errUnsupportedSubsamplingRatio + } + case 1: // Cb. + if d.comp[0].h%h != 0 || d.comp[0].v%v != 0 { + return errUnsupportedSubsamplingRatio + } + case 2: // Cr. + if d.comp[1].h != h || d.comp[1].v != v { + return errUnsupportedSubsamplingRatio + } + } + + case 4: + // For 4-component images (either CMYK or YCbCrK), we only support two + // hv vectors: [0x11 0x11 0x11 0x11] and [0x22 0x11 0x11 0x22]. + // Theoretically, 4-component JPEG images could mix and match hv values + // but in practice, those two combinations are the only ones in use, + // and it simplifies the applyBlack code below if we can assume that: + // - for CMYK, the C and K channels have full samples, and if the M + // and Y channels subsample, they subsample both horizontally and + // vertically. + // - for YCbCrK, the Y and K channels have full samples. + switch i { + case 0: + if hv != 0x11 && hv != 0x22 { + return errUnsupportedSubsamplingRatio + } + case 1, 2: + if hv != 0x11 { + return errUnsupportedSubsamplingRatio + } + case 3: + if d.comp[0].h != h || d.comp[0].v != v { + return errUnsupportedSubsamplingRatio + } + } + } + + d.comp[i].h = h + d.comp[i].v = v + } + return nil +} + +// Specified in section B.2.4.1. +func (d *decoder) processDQT(n int) error { +loop: + for n > 0 { + n-- + x, err := d.readByte() + if err != nil { + return err + } + tq := x & 0x0f + if tq > maxTq { + return FormatError("bad Tq value") + } + switch x >> 4 { + default: + return FormatError("bad Pq value") + case 0: + if n < blockSize { + break loop + } + n -= blockSize + if err := d.readFull(d.tmp[:blockSize]); err != nil { + return err + } + for i := range d.quant[tq] { + d.quant[tq][i] = int32(d.tmp[i]) + } + case 1: + if n < 2*blockSize { + break loop + } + n -= 2 * blockSize + if err := d.readFull(d.tmp[:2*blockSize]); err != nil { + return err + } + for i := range d.quant[tq] { + d.quant[tq][i] = int32(d.tmp[2*i])<<8 | int32(d.tmp[2*i+1]) + } + } + } + if n != 0 { + return FormatError("DQT has wrong length") + } + return nil +} + +// Specified in section B.2.4.4. +func (d *decoder) processDRI(n int) error { + if n != 2 { + return FormatError("DRI has wrong length") + } + if err := d.readFull(d.tmp[:2]); err != nil { + return err + } + d.ri = int(d.tmp[0])<<8 + int(d.tmp[1]) + return nil +} + +func (d *decoder) processApp0Marker(n int) error { + if n < 5 { + return d.ignore(n) + } + if err := d.readFull(d.tmp[:5]); err != nil { + return err + } + n -= 5 + + d.jfif = d.tmp[0] == 'J' && d.tmp[1] == 'F' && d.tmp[2] == 'I' && d.tmp[3] == 'F' && d.tmp[4] == '\x00' + + if n > 0 { + return d.ignore(n) + } + return nil +} + +func (d *decoder) processApp14Marker(n int) error { + if n < 12 { + return d.ignore(n) + } + if err := d.readFull(d.tmp[:12]); err != nil { + return err + } + n -= 12 + + if d.tmp[0] == 'A' && d.tmp[1] == 'd' && d.tmp[2] == 'o' && d.tmp[3] == 'b' && d.tmp[4] == 'e' { + d.adobeTransformValid = true + d.adobeTransform = d.tmp[11] + } + + if n > 0 { + return d.ignore(n) + } + return nil +} + +// decode reads a JPEG image from r and returns it as an image.Image. +func (d *decoder) decode(r io.Reader, configOnly bool) (image.Image, error) { + d.r = r + + // Check for the Start Of Image marker. + if err := d.readFull(d.tmp[:2]); err != nil { + return nil, err + } + if d.tmp[0] != 0xff || d.tmp[1] != soiMarker { + return nil, FormatError("missing SOI marker") + } + + // Process the remaining segments until the End Of Image marker. + for { + err := d.readFull(d.tmp[:2]) + if err != nil { + return nil, err + } + for d.tmp[0] != 0xff { + // Strictly speaking, this is a format error. However, libjpeg is + // liberal in what it accepts. As of version 9, next_marker in + // jdmarker.c treats this as a warning (JWRN_EXTRANEOUS_DATA) and + // continues to decode the stream. Even before next_marker sees + // extraneous data, jpeg_fill_bit_buffer in jdhuff.c reads as many + // bytes as it can, possibly past the end of a scan's data. It + // effectively puts back any markers that it overscanned (e.g. an + // "\xff\xd9" EOI marker), but it does not put back non-marker data, + // and thus it can silently ignore a small number of extraneous + // non-marker bytes before next_marker has a chance to see them (and + // print a warning). + // + // We are therefore also liberal in what we accept. Extraneous data + // is silently ignored. + // + // This is similar to, but not exactly the same as, the restart + // mechanism within a scan (the RST[0-7] markers). + // + // Note that extraneous 0xff bytes in e.g. SOS data are escaped as + // "\xff\x00", and so are detected a little further down below. + d.tmp[0] = d.tmp[1] + d.tmp[1], err = d.readByte() + if err != nil { + return nil, err + } + } + marker := d.tmp[1] + if marker == 0 { + // Treat "\xff\x00" as extraneous data. + continue + } + for marker == 0xff { + // Section B.1.1.2 says, "Any marker may optionally be preceded by any + // number of fill bytes, which are bytes assigned code X'FF'". + marker, err = d.readByte() + if err != nil { + return nil, err + } + } + if marker == eoiMarker { // End Of Image. + break + } + if rst0Marker <= marker && marker <= rst7Marker { + // Figures B.2 and B.16 of the specification suggest that restart markers should + // only occur between Entropy Coded Segments and not after the final ECS. + // However, some encoders may generate incorrect JPEGs with a final restart + // marker. That restart marker will be seen here instead of inside the processSOS + // method, and is ignored as a harmless error. Restart markers have no extra data, + // so we check for this before we read the 16-bit length of the segment. + continue + } + + // Read the 16-bit length of the segment. The value includes the 2 bytes for the + // length itself, so we subtract 2 to get the number of remaining bytes. + if err = d.readFull(d.tmp[:2]); err != nil { + return nil, err + } + n := int(d.tmp[0])<<8 + int(d.tmp[1]) - 2 + if n < 0 { + return nil, FormatError("short segment length") + } + + switch marker { + case sof0Marker, sof1Marker, sof2Marker: + d.baseline = marker == sof0Marker + d.progressive = marker == sof2Marker + err = d.processSOF(n) + if configOnly && d.jfif { + return nil, err + } + case dhtMarker: + if configOnly { + err = d.ignore(n) + } else { + err = d.processDHT(n) + } + case dqtMarker: + if configOnly { + err = d.ignore(n) + } else { + err = d.processDQT(n) + } + case sosMarker: + if configOnly { + return nil, nil + } + err = d.processSOS(n) + case driMarker: + if configOnly { + err = d.ignore(n) + } else { + err = d.processDRI(n) + } + case app0Marker: + err = d.processApp0Marker(n) + case app14Marker: + err = d.processApp14Marker(n) + default: + if app0Marker <= marker && marker <= app15Marker || marker == comMarker { + err = d.ignore(n) + } else if marker < 0xc0 { // See Table B.1 "Marker code assignments". + err = FormatError("unknown marker") + } else { + err = UnsupportedError("unknown marker") + } + } + if err != nil { + return nil, err + } + } + + if d.progressive { + if err := d.reconstructProgressiveImage(); err != nil { + return nil, err + } + } + if d.img1 != nil { + return d.img1, nil + } + if d.img3 != nil { + if d.blackPix != nil { + return d.applyBlack() + } else if d.isRGB() { + return d.convertToRGB() + } + return d.img3, nil + } + return nil, FormatError("missing SOS marker") +} + +// applyBlack combines d.img3 and d.blackPix into a CMYK image. The formula +// used depends on whether the JPEG image is stored as CMYK or YCbCrK, +// indicated by the APP14 (Adobe) metadata. +// +// Adobe CMYK JPEG images are inverted, where 255 means no ink instead of full +// ink, so we apply "v = 255 - v" at various points. Note that a double +// inversion is a no-op, so inversions might be implicit in the code below. +func (d *decoder) applyBlack() (image.Image, error) { + if !d.adobeTransformValid { + return nil, UnsupportedError("unknown color model: 4-component JPEG doesn't have Adobe APP14 metadata") + } + + // If the 4-component JPEG image isn't explicitly marked as "Unknown (RGB + // or CMYK)" as per + // https://www.sno.phy.queensu.ca/~phil/exiftool/TagNames/JPEG.html#Adobe + // we assume that it is YCbCrK. This matches libjpeg's jdapimin.c. + if d.adobeTransform != adobeTransformUnknown { + // Convert the YCbCr part of the YCbCrK to RGB, invert the RGB to get + // CMY, and patch in the original K. The RGB to CMY inversion cancels + // out the 'Adobe inversion' described in the applyBlack doc comment + // above, so in practice, only the fourth channel (black) is inverted. + bounds := d.img3.Bounds() + img := image.NewRGBA(bounds) + imageutil.DrawYCbCr(img, bounds, d.img3, bounds.Min) + for iBase, y := 0, bounds.Min.Y; y < bounds.Max.Y; iBase, y = iBase+img.Stride, y+1 { + for i, x := iBase+3, bounds.Min.X; x < bounds.Max.X; i, x = i+4, x+1 { + img.Pix[i] = 255 - d.blackPix[(y-bounds.Min.Y)*d.blackStride+(x-bounds.Min.X)] + } + } + return &image.CMYK{ + Pix: img.Pix, + Stride: img.Stride, + Rect: img.Rect, + }, nil + } + + // The first three channels (cyan, magenta, yellow) of the CMYK + // were decoded into d.img3, but each channel was decoded into a separate + // []byte slice, and some channels may be subsampled. We interleave the + // separate channels into an image.CMYK's single []byte slice containing 4 + // contiguous bytes per pixel. + bounds := d.img3.Bounds() + img := image.NewCMYK(bounds) + + translations := [4]struct { + src []byte + stride int + }{ + {d.img3.Y, d.img3.YStride}, + {d.img3.Cb, d.img3.CStride}, + {d.img3.Cr, d.img3.CStride}, + {d.blackPix, d.blackStride}, + } + for t, translation := range translations { + subsample := d.comp[t].h != d.comp[0].h || d.comp[t].v != d.comp[0].v + for iBase, y := 0, bounds.Min.Y; y < bounds.Max.Y; iBase, y = iBase+img.Stride, y+1 { + sy := y - bounds.Min.Y + if subsample { + sy /= 2 + } + for i, x := iBase+t, bounds.Min.X; x < bounds.Max.X; i, x = i+4, x+1 { + sx := x - bounds.Min.X + if subsample { + sx /= 2 + } + img.Pix[i] = 255 - translation.src[sy*translation.stride+sx] + } + } + } + return img, nil +} + +func (d *decoder) isRGB() bool { + if d.jfif { + return false + } + if d.adobeTransformValid && d.adobeTransform == adobeTransformUnknown { + // https://www.sno.phy.queensu.ca/~phil/exiftool/TagNames/JPEG.html#Adobe + // says that 0 means Unknown (and in practice RGB) and 1 means YCbCr. + return true + } + return d.comp[0].c == 'R' && d.comp[1].c == 'G' && d.comp[2].c == 'B' +} + +func (d *decoder) convertToRGB() (image.Image, error) { + cScale := d.comp[0].h / d.comp[1].h + bounds := d.img3.Bounds() + img := image.NewRGBA(bounds) + for y := bounds.Min.Y; y < bounds.Max.Y; y++ { + po := img.PixOffset(bounds.Min.X, y) + yo := d.img3.YOffset(bounds.Min.X, y) + co := d.img3.COffset(bounds.Min.X, y) + for i, iMax := 0, bounds.Max.X-bounds.Min.X; i < iMax; i++ { + img.Pix[po+4*i+0] = d.img3.Y[yo+i] + img.Pix[po+4*i+1] = d.img3.Cb[co+i/cScale] + img.Pix[po+4*i+2] = d.img3.Cr[co+i/cScale] + img.Pix[po+4*i+3] = 255 + } + } + return img, nil +} + +// Decode reads a JPEG image from r and returns it as an image.Image. +func Decode(r io.Reader) (image.Image, error) { + var d decoder + return d.decode(r, false) +} + +// DecodeConfig returns the color model and dimensions of a JPEG image without +// decoding the entire image. +func DecodeConfig(r io.Reader) (image.Config, error) { + var d decoder + if _, err := d.decode(r, true); err != nil { + return image.Config{}, err + } + switch d.nComp { + case 1: + return image.Config{ + ColorModel: color.GrayModel, + Width: d.width, + Height: d.height, + }, nil + case 3: + cm := color.YCbCrModel + if d.isRGB() { + cm = color.RGBAModel + } + return image.Config{ + ColorModel: cm, + Width: d.width, + Height: d.height, + }, nil + case 4: + return image.Config{ + ColorModel: color.CMYKModel, + Width: d.width, + Height: d.height, + }, nil + } + return image.Config{}, FormatError("missing SOF marker") +} + +func init() { + image.RegisterFormat("jpeg", "\xff\xd8", Decode, DecodeConfig) +} diff --git a/src/image/jpeg/reader_test.go b/src/image/jpeg/reader_test.go new file mode 100644 index 0000000..bf07fad --- /dev/null +++ b/src/image/jpeg/reader_test.go @@ -0,0 +1,517 @@ +// Copyright 2012 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package jpeg + +import ( + "bytes" + "encoding/base64" + "fmt" + "image" + "image/color" + "io" + "math/rand" + "os" + "strings" + "testing" + "time" +) + +// TestDecodeProgressive tests that decoding the baseline and progressive +// versions of the same image result in exactly the same pixel data, in YCbCr +// space for color images, and Y space for grayscale images. +func TestDecodeProgressive(t *testing.T) { + testCases := []string{ + "../testdata/video-001", + "../testdata/video-001.q50.410", + "../testdata/video-001.q50.411", + "../testdata/video-001.q50.420", + "../testdata/video-001.q50.422", + "../testdata/video-001.q50.440", + "../testdata/video-001.q50.444", + "../testdata/video-005.gray.q50", + "../testdata/video-005.gray.q50.2x2", + "../testdata/video-001.separate.dc.progression", + } + for _, tc := range testCases { + m0, err := decodeFile(tc + ".jpeg") + if err != nil { + t.Errorf("%s: %v", tc+".jpeg", err) + continue + } + m1, err := decodeFile(tc + ".progressive.jpeg") + if err != nil { + t.Errorf("%s: %v", tc+".progressive.jpeg", err) + continue + } + if m0.Bounds() != m1.Bounds() { + t.Errorf("%s: bounds differ: %v and %v", tc, m0.Bounds(), m1.Bounds()) + continue + } + // All of the video-*.jpeg files are 150x103. + if m0.Bounds() != image.Rect(0, 0, 150, 103) { + t.Errorf("%s: bad bounds: %v", tc, m0.Bounds()) + continue + } + + switch m0 := m0.(type) { + case *image.YCbCr: + m1 := m1.(*image.YCbCr) + if err := check(m0.Bounds(), m0.Y, m1.Y, m0.YStride, m1.YStride); err != nil { + t.Errorf("%s (Y): %v", tc, err) + continue + } + if err := check(m0.Bounds(), m0.Cb, m1.Cb, m0.CStride, m1.CStride); err != nil { + t.Errorf("%s (Cb): %v", tc, err) + continue + } + if err := check(m0.Bounds(), m0.Cr, m1.Cr, m0.CStride, m1.CStride); err != nil { + t.Errorf("%s (Cr): %v", tc, err) + continue + } + case *image.Gray: + m1 := m1.(*image.Gray) + if err := check(m0.Bounds(), m0.Pix, m1.Pix, m0.Stride, m1.Stride); err != nil { + t.Errorf("%s: %v", tc, err) + continue + } + default: + t.Errorf("%s: unexpected image type %T", tc, m0) + continue + } + } +} + +func decodeFile(filename string) (image.Image, error) { + f, err := os.Open(filename) + if err != nil { + return nil, err + } + defer f.Close() + return Decode(f) +} + +type eofReader struct { + data []byte // deliver from Read without EOF + dataEOF []byte // then deliver from Read with EOF on last chunk + lenAtEOF int +} + +func (r *eofReader) Read(b []byte) (n int, err error) { + if len(r.data) > 0 { + n = copy(b, r.data) + r.data = r.data[n:] + } else { + n = copy(b, r.dataEOF) + r.dataEOF = r.dataEOF[n:] + if len(r.dataEOF) == 0 { + err = io.EOF + if r.lenAtEOF == -1 { + r.lenAtEOF = n + } + } + } + return +} + +func TestDecodeEOF(t *testing.T) { + // Check that if reader returns final data and EOF at same time, jpeg handles it. + data, err := os.ReadFile("../testdata/video-001.jpeg") + if err != nil { + t.Fatal(err) + } + + n := len(data) + for i := 0; i < n; { + r := &eofReader{data[:n-i], data[n-i:], -1} + _, err := Decode(r) + if err != nil { + t.Errorf("Decode with Read() = %d, EOF: %v", r.lenAtEOF, err) + } + if i == 0 { + i = 1 + } else { + i *= 2 + } + } +} + +// check checks that the two pix data are equal, within the given bounds. +func check(bounds image.Rectangle, pix0, pix1 []byte, stride0, stride1 int) error { + if stride0 <= 0 || stride0%8 != 0 { + return fmt.Errorf("bad stride %d", stride0) + } + if stride1 <= 0 || stride1%8 != 0 { + return fmt.Errorf("bad stride %d", stride1) + } + // Compare the two pix data, one 8x8 block at a time. + for y := 0; y < len(pix0)/stride0 && y < len(pix1)/stride1; y += 8 { + for x := 0; x < stride0 && x < stride1; x += 8 { + if x >= bounds.Max.X || y >= bounds.Max.Y { + // We don't care if the two pix data differ if the 8x8 block is + // entirely outside of the image's bounds. For example, this can + // occur with a 4:2:0 chroma subsampling and a 1x1 image. Baseline + // decoding works on the one 16x16 MCU as a whole; progressive + // decoding's first pass works on that 16x16 MCU as a whole but + // refinement passes only process one 8x8 block within the MCU. + continue + } + + for j := 0; j < 8; j++ { + for i := 0; i < 8; i++ { + index0 := (y+j)*stride0 + (x + i) + index1 := (y+j)*stride1 + (x + i) + if pix0[index0] != pix1[index1] { + return fmt.Errorf("blocks at (%d, %d) differ:\n%sand\n%s", x, y, + pixString(pix0, stride0, x, y), + pixString(pix1, stride1, x, y), + ) + } + } + } + } + } + return nil +} + +func pixString(pix []byte, stride, x, y int) string { + s := bytes.NewBuffer(nil) + for j := 0; j < 8; j++ { + fmt.Fprintf(s, "\t") + for i := 0; i < 8; i++ { + fmt.Fprintf(s, "%02x ", pix[(y+j)*stride+(x+i)]) + } + fmt.Fprintf(s, "\n") + } + return s.String() +} + +func TestTruncatedSOSDataDoesntPanic(t *testing.T) { + b, err := os.ReadFile("../testdata/video-005.gray.q50.jpeg") + if err != nil { + t.Fatal(err) + } + sosMarker := []byte{0xff, 0xda} + i := bytes.Index(b, sosMarker) + if i < 0 { + t.Fatal("SOS marker not found") + } + i += len(sosMarker) + j := i + 10 + if j > len(b) { + j = len(b) + } + for ; i < j; i++ { + Decode(bytes.NewReader(b[:i])) + } +} + +func TestLargeImageWithShortData(t *testing.T) { + // This input is an invalid JPEG image, based on the fuzzer-generated image + // in issue 10413. It is only 504 bytes, and shouldn't take long for Decode + // to return an error. The Start Of Frame marker gives the image dimensions + // as 8192 wide and 8192 high, so even if an unreadByteStuffedByte bug + // doesn't technically lead to an infinite loop, such a bug can still cause + // an unreasonably long loop for such a short input. + const input = "" + + "\xff\xd8\xff\xe0\x00\x10\x4a\x46\x49\x46\x00\x01\x01\x00\x00\x01" + + "\x00\x01\x00\x00\xff\xdb\x00\x43\x00\x10\x0b\x0c\x0e\x0c\x0a\x10" + + "\x0e\x89\x0e\x12\x11\x10\x13\x18\xff\xd8\xff\xe0\x00\x10\x4a\x46" + + "\x49\x46\x00\x01\x01\x00\x00\x01\x00\x01\x00\x00\xff\xdb\x00\x43" + + "\x00\x10\x0b\x0c\x0e\x0c\x0a\x10\x0e\x0d\x0e\x12\x11\x10\x13\x18" + + "\x28\x1a\x18\x16\x16\x18\x31\x23\x25\x1d\x28\x3a\x33\x3d\x3c\x39" + + "\x33\x38\x37\x40\x48\x5c\x4e\x40\x44\x57\x45\x37\x38\x50\x6d\x51" + + "\x57\x5f\x62\x67\x68\x67\x3e\x4d\x71\x79\x70\x64\x78\x5c\x65\x67" + + "\x63\xff\xc0\x00\x0b\x08\x20\x00\x20\x00\x01\x01\x11\x00\xff\xc4" + + "\x00\x1f\x00\x00\x01\x05\x01\x01\x01\x01\x01\x01\x00\x00\x00\x00" + + "\x00\x00\x00\x00\x01\x02\x03\x04\x05\x06\x07\x08\x09\x0a\x0b\xff" + + "\xc4\x00\xb5\x10\x00\x02\x01\x03\x03\x02\x04\x03\x05\x05\x04\x04" + + "\x00\x00\x01\x7d\x01\x02\x03\x00\x04\x11\x05\x12\x21\x31\x01\x06" + + "\x13\x51\x61\x07\x22\x71\x14\x32\x81\x91\xa1\x08\x23\xd8\xff\xdd" + + "\x42\xb1\xc1\x15\x52\xd1\xf0\x24\x33\x62\x72\x82\x09\x0a\x16\x17" + + "\x18\x19\x1a\x25\x26\x27\x28\x29\x2a\x34\x35\x36\x37\x38\x39\x3a" + + "\x43\x44\x45\x46\x47\x48\x49\x4a\x53\x54\x55\x56\x57\x58\x59\x5a" + + "\x00\x63\x64\x65\x66\x67\x68\x69\x6a\x73\x74\x75\x76\x77\x78\x79" + + "\x7a\x83\x84\x85\x86\x87\x88\x89\x8a\x92\x93\x94\x95\x96\x97\x98" + + "\x99\x9a\xa2\xa3\xa4\xa5\xa6\xa7\xa8\xa9\xaa\xb2\xb3\xb4\xb5\xb6" + + "\xb7\xb8\xb9\xba\xc2\xc3\xc4\xc5\xc6\xc7\xff\xd8\xff\xe0\x00\x10" + + "\x4a\x46\x49\x46\x00\x01\x01\x00\x00\x01\x00\x01\x00\x00\xff\xdb" + + "\x00\x43\x00\x10\x0b\x0c\x0e\x0c\x0a\x10\x0e\x0d\x0e\x12\x11\x10" + + "\x13\x18\x28\x1a\x18\x16\x16\x18\x31\x23\x25\x1d\xc8\xc9\xca\xd2" + + "\xd3\xd4\xd5\xd6\xd7\xd8\xd9\xda\xe1\xe2\xe3\xe4\xe5\xe6\xe7\xe8" + + "\xe9\xea\xf1\xf2\xf3\xf4\xf5\xf6\xf7\xf8\xf9\xfa\xff\xda\x00\x08" + + "\x01\x01\x00\x00\x3f\x00\xb9\xeb\x50\xb0\xdb\xc8\xa8\xe4\x63\x80" + + "\xdd\x31\xd6\x9d\xbb\xf2\xc5\x42\x1f\x6c\x6f\xf4\x34\xdd\x3c\xfc" + + "\xac\xe7\x3d\x80\xa9\xcc\x87\x34\xb3\x37\xfa\x2b\x9f\x6a\xad\x63" + + "\x20\x36\x9f\x78\x64\x75\xe6\xab\x7d\xb2\xde\x29\x70\xd3\x20\x27" + + "\xde\xaf\xa4\xf0\xca\x9f\x24\xa8\xdf\x46\xa8\x24\x84\x96\xe3\x77" + + "\xf9\x2e\xe0\x0a\x62\x7f\xdf\xd9" + c := make(chan error, 1) + go func() { + _, err := Decode(strings.NewReader(input)) + c <- err + }() + select { + case err := <-c: + if err == nil { + t.Fatalf("got nil error, want non-nil") + } + case <-time.After(3 * time.Second): + t.Fatalf("timed out") + } +} + +func TestPaddedRSTMarker(t *testing.T) { + // This test image comes from golang.org/issue/28717 + const base64EncodedImage = ` +/9j/4AAhQVZJMQABAQEAeAB4AAAAAAAAAAAAAAAAAAAAAAAAAP/bAEMABAIDAwMCBAMDAwQEBAQGCgYG +BQUGDAgJBwoODA8PDgwODxASFxMQERURDQ4UGhQVFxgZGhkPExweHBkeFxkZGP/bAEMBBAQEBgUGCwYG +CxgQDhAYGBgYGBgYGBgYGBgYGBgYGBgYGBgYGBgYGBgYGBgYGBgYGBgYGBgYGBgYGBgYGBgYGP/EAaIA +AAEFAQEBAQEBAAAAAAAAAAABAgMEBQYHCAkKCxAAAgEDAwIEAwUFBAQAAAF9AQIDAAQRBRIhMUEGE1Fh +ByJxFDKBkaEII0KxwRVS0fAkM2JyggkKFhcYGRolJicoKSo0NTY3ODk6Q0RFRkdISUpTVFVWV1hZWmNk +ZWZnaGlqc3R1dnd4eXqDhIWGh4iJipKTlJWWl5iZmqKjpKWmp6ipqrKztLW2t7i5usLDxMXGx8jJytLT +1NXW19jZ2uHi4+Tl5ufo6erx8vP09fb3+Pn6AQADAQEBAQEBAQEBAAAAAAAAAQIDBAUGBwgJCgsRAAIB +AgQEAwQHBQQEAAECdwABAgMRBAUhMQYSQVEHYXETIjKBCBRCkaGxwQkjM1LwFWJy0QoWJDThJfEXGBka +JicoKSo1Njc4OTpDREVGR0hJSlNUVVZXWFlaY2RlZmdoaWpzdHV2d3h5eoKDhIWGh4iJipKTlJWWl5iZ +mqKjpKWmp6ipqrKztLW2t7i5usLDxMXGx8jJytLT1NXW19jZ2uLj5OXm5+jp6vLz9PX29/j5+v/dAAQA +Cv/gAAQAAP/AABEIALABQAMBIQACEQEDEQH/2gAMAwEAAhEDEQA/APnCFTk5BPPGKliAB718W7H2j3Ip +VUuwJxzTfKXacde9VBhYRUBAyO3pTmUAbSMU5WGmybywzHGAMdelPVFC+n1qXZCuyaJADxjj2qzbBMAP +xz1rKaVib6ltLcFvlIx2pLy0dwuAMMBnH1rFON9RNsszAZPFEYHldPzrOy3KewmBk9qUABugxjtTVmiW +xWRcjp+VJtHXgVL3K6AgBDdM9eRTNzAZViOe1VyxaJavuf/Q8aW4mUcSGpo764AyHz+FfnnJBvVH1UsN +CS1Q/wDte4Trip49ecA7g3FSqMW9zlqZandxJ4/EKADcSPqKni8QQMT865qOSUNjiqZdNbFiHWYXz84N +WE1KNsfMKj2zirHHPDSj0JFvo2H36d9pUjg1sqykYOm0KbgY60omXPXmr9pFkco3zBnrQzjGcnrRzp9S +bEbuOvao3fisZSXUpIYWGKGcbetTCSswsxnmACkYrtNSpJ2YNM//0fnK1BD7sDg9KmUHeOe/Svid3qfb +SdmQ3AHmnr1pGBC5z19a0hohNiJkensM1J0yCKmY0yZR82e+BT1BxnpmpepN9SRCR0NSpweOoPWs6isr +ijuWIZGBA/lVwzMVFY8ibuhXEfr+tOz8hIqUymhRnJGTSc5wBVRRDFPXBHJpB3qdmV0EX7vXmoyfl685 +p2dxWR//0vFsHZ9TQv3T618Bqz7PSwwn1phPXpSWrQEUhIx0NVXc7j0rSNwViCS4dWYpJj3BpBqVzGy7 +ZmHSq9kpblSpxkveQ+PX7uMf6wEDtU0fi24TAkX8jTeCjJaaHDUwFN7aFq28aL/GCMGrtr4xtHGGkA+t +YTy+a+E82eAa2LsXiWzI5mXPHercOsW8hwJB+dcUqVSCOKVFxdmiwl7E2MOPzp4nQ9GH51jzNbmUoOIC +TI4okOaUXoybDCevNBPHX8qIO4mf/9P52i4dix5zjp/n1qZFBCmviL6an2kt9CGcYnJznJpOBwegq4vQ +L9xIUytSkfu/bv70p7j6EnQgjHSpFGVqXclkkaHb1+makUHgdazm7IFuSKOasrnjis2+oDm9qnIHlgd/ +es7gxqjkt1NLwH4xTTEhjkhutM3D15oGhkcnBGRTDKu3A7H1rS3cLn//1PEhJ8uM557UvmDaa/P7a3Ps +xpZcZ6mo5WG45pdUC2K8ko5JIzWfcTqu7HPHrW9OLbKWhSluVLNz3wKrS3I3KfcV1Rg9CrpXK8l0F7io +pLnLnJHGOldMYJGMpu5XNwuxjyRTBcAAjd1HWtfZmPORy3WAWWQDOM4PWtHRru6DFlmY88ZqKsVyXaKp +QjOoa7axe28G/cWqhoHjO/n1WeJwSkS9c981wUcFCopPayFj8JC8VFbs6e38VldvmHHFaMHimAoCzDB6 +V5U8FKz5TlrZU4/CXYtdtnXIarEepW7jAcfnXGqEoKx5tfBzh0P/1fnqEAsc/wB6pI9owAD1618Qn3Ps +35EE4UzHrx79aXaMcdaqAMWIADvj271IMeXg59KUmNLQkUDfjb1FSLxzg0pWJRLGAQAeMVIoA+uaxlaw +0SoF/u1KowwwDUcwuo9wMjrUrY2ZPOKy0KY1T1NMdwG/CtBEFzMqnIPNUZ75FBJP5mtIQvYfoU21JFVs +N271AurRE/e611xw73Yj/9b50GsQhOXHWnpq8JX7w4PWvjPq76H2fzHjVYCud9Q3GrRAZDUvq75kNbMz +7vV0zjdjNZ82pqzMcj7tdlPDtIiVWKKct+AxwRxUbXi7VPJAIrZUdEZOsrsga8DFgelQtd98g5P6V0Qp +GE6qIUut2cZ470kd2FjYc4Oce1bSpJ3Rzxq21GNcDZhSeg710ujKRbKzAg5rkxceWnqd+XtOo7bD9cl8 +qxLDPHasXwUvmyXU7Lgl8cegrnw2lGbZ14l3rU0bl3gMQCRgVU1y7WytUZQzMRwBXPRhzWRvVny3ZW8N +6xPdXBikiZc5IOa6GG6nDsd5xnAyfaliqEacrGOHarx5pI//1/nuL754HWngEkYx1r4VWsfaMjk4mP8A 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+xjOa96xwWstD/9D451XAhBOOTxVRlURdOa8ymrI9epu2SW23cMgDHb1qw4BcrgY9KJ25kOn8LLFsArYG +McVIu3GdvOOTWLV2axeliOYgM+FzmoL1isAwME4GKVloDvqVoI9zEEAMMGrbIAmFUdcZrSbS0MqcWQBg +0WMg4PalhCFCdpHWiXUFZtaDtqhywBwMY9Ko6sR5oXPTn2p09WianVIyEYebwMEnPNTL5eXBA4Hautp6 +WONSWt0TQMhUgjKj1q5bhQWKMDwBxWE20mbws3ElXy9pUEDqMd6hfaHUgE7B2HtWUO7NKiVrI//R8Vj4 +br37VMuT9TX55HY+ze+gMM5PSkzwR1AoWu4IRRg9akPC8HpSlfRFLXYeCN3TkipV60ulmBJGeR71IvTP +Ws5K6Ghwp3FQkMH6elNJ461didOoq9SaRjxSjqwuVbgZkH1rzrxWwk8QXj9hIR+XFejl1nVt5EV/gM2I +qCTjPTH50x+eRxya961tzzt9j//S+O9WJ+zjgDmqJYGDJYZNedSSaPXqu0tew+L7wPTvmrBO5x7Y5qZf +EnYUPhZdhUZyO3pTgcOxGOR0rnbu7M6fhK9yVEvPy59O9QX75VBjnIoS+ETa95DLbdu6nnp7VYGSMk59 +vxrWemxlTZCvMe4BTg/nSRKHVsjGfpSe90C1VmTsG2H2x3rF1J1eVxgcHr+FVQWtyK7srFGAgOrHqDnp +7VPGNzO/O3kkCut7pnGno0idCCNyt6Crca5ZiDjpgVzXsnc6X71rDyBgcbtucn8KhjBMpOfrz7VlTdtT +Sqm7JH//2Q== +` + + data, err := base64.StdEncoding.DecodeString(base64EncodedImage) + if err != nil { + t.Fatalf("base64 DecodeString: %v", err) + } + if _, err = Decode(bytes.NewReader(data)); err != nil { + t.Fatalf("Decode: %v", err) + } +} + +func TestExtraneousData(t *testing.T) { + // Encode a 1x1 red image. + src := image.NewRGBA(image.Rect(0, 0, 1, 1)) + src.Set(0, 0, color.RGBA{0xff, 0x00, 0x00, 0xff}) + buf := new(bytes.Buffer) + if err := Encode(buf, src, nil); err != nil { + t.Fatalf("encode: %v", err) + } + enc := buf.String() + // Sanity check that the encoded JPEG is long enough, that it ends in a + // "\xff\xd9" EOI marker, and that it contains a "\xff\xda" SOS marker + // somewhere in the final 64 bytes. + if len(enc) < 64 { + t.Fatalf("encoded JPEG is too short: %d bytes", len(enc)) + } + if got, want := enc[len(enc)-2:], "\xff\xd9"; got != want { + t.Fatalf("encoded JPEG ends with %q, want %q", got, want) + } + if s := enc[len(enc)-64:]; !strings.Contains(s, "\xff\xda") { + t.Fatalf("encoded JPEG does not contain a SOS marker (ff da) near the end: % x", s) + } + // Test that adding some random junk between the SOS marker and the + // EOI marker does not affect the decoding. + rnd := rand.New(rand.NewSource(1)) + for i, nerr := 0, 0; i < 1000 && nerr < 10; i++ { + buf.Reset() + // Write all but the trailing "\xff\xd9" EOI marker. + buf.WriteString(enc[:len(enc)-2]) + // Write some random extraneous data. + for n := rnd.Intn(10); n > 0; n-- { + if x := byte(rnd.Intn(256)); x != 0xff { + buf.WriteByte(x) + } else { + // The JPEG format escapes a SOS 0xff data byte as "\xff\x00". + buf.WriteString("\xff\x00") + } + } + // Write the "\xff\xd9" EOI marker. + buf.WriteString("\xff\xd9") + + // Check that we can still decode the resultant image. + got, err := Decode(buf) + if err != nil { + t.Errorf("could not decode image #%d: %v", i, err) + nerr++ + continue + } + if got.Bounds() != src.Bounds() { + t.Errorf("image #%d, bounds differ: %v and %v", i, got.Bounds(), src.Bounds()) + nerr++ + continue + } + if averageDelta(got, src) > 2<<8 { + t.Errorf("image #%d changed too much after a round trip", i) + nerr++ + continue + } + } +} + +func benchmarkDecode(b *testing.B, filename string) { + data, err := os.ReadFile(filename) + if err != nil { + b.Fatal(err) + } + cfg, err := DecodeConfig(bytes.NewReader(data)) + if err != nil { + b.Fatal(err) + } + b.SetBytes(int64(cfg.Width * cfg.Height * 4)) + b.ReportAllocs() + b.ResetTimer() + for i := 0; i < b.N; i++ { + Decode(bytes.NewReader(data)) + } +} + +func BenchmarkDecodeBaseline(b *testing.B) { + benchmarkDecode(b, "../testdata/video-001.jpeg") +} + +func BenchmarkDecodeProgressive(b *testing.B) { + benchmarkDecode(b, "../testdata/video-001.progressive.jpeg") +} diff --git a/src/image/jpeg/scan.go b/src/image/jpeg/scan.go new file mode 100644 index 0000000..94f3d3a --- /dev/null +++ b/src/image/jpeg/scan.go @@ -0,0 +1,523 @@ +// Copyright 2012 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package jpeg + +import ( + "image" +) + +// makeImg allocates and initializes the destination image. +func (d *decoder) makeImg(mxx, myy int) { + if d.nComp == 1 { + m := image.NewGray(image.Rect(0, 0, 8*mxx, 8*myy)) + d.img1 = m.SubImage(image.Rect(0, 0, d.width, d.height)).(*image.Gray) + return + } + + h0 := d.comp[0].h + v0 := d.comp[0].v + hRatio := h0 / d.comp[1].h + vRatio := v0 / d.comp[1].v + var subsampleRatio image.YCbCrSubsampleRatio + switch hRatio<<4 | vRatio { + case 0x11: + subsampleRatio = image.YCbCrSubsampleRatio444 + case 0x12: + subsampleRatio = image.YCbCrSubsampleRatio440 + case 0x21: + subsampleRatio = image.YCbCrSubsampleRatio422 + case 0x22: + subsampleRatio = image.YCbCrSubsampleRatio420 + case 0x41: + subsampleRatio = image.YCbCrSubsampleRatio411 + case 0x42: + subsampleRatio = image.YCbCrSubsampleRatio410 + default: + panic("unreachable") + } + m := image.NewYCbCr(image.Rect(0, 0, 8*h0*mxx, 8*v0*myy), subsampleRatio) + d.img3 = m.SubImage(image.Rect(0, 0, d.width, d.height)).(*image.YCbCr) + + if d.nComp == 4 { + h3, v3 := d.comp[3].h, d.comp[3].v + d.blackPix = make([]byte, 8*h3*mxx*8*v3*myy) + d.blackStride = 8 * h3 * mxx + } +} + +// Specified in section B.2.3. +func (d *decoder) processSOS(n int) error { + if d.nComp == 0 { + return FormatError("missing SOF marker") + } + if n < 6 || 4+2*d.nComp < n || n%2 != 0 { + return FormatError("SOS has wrong length") + } + if err := d.readFull(d.tmp[:n]); err != nil { + return err + } + nComp := int(d.tmp[0]) + if n != 4+2*nComp { + return FormatError("SOS length inconsistent with number of components") + } + var scan [maxComponents]struct { + compIndex uint8 + td uint8 // DC table selector. + ta uint8 // AC table selector. + } + totalHV := 0 + for i := 0; i < nComp; i++ { + cs := d.tmp[1+2*i] // Component selector. + compIndex := -1 + for j, comp := range d.comp[:d.nComp] { + if cs == comp.c { + compIndex = j + } + } + if compIndex < 0 { + return FormatError("unknown component selector") + } + scan[i].compIndex = uint8(compIndex) + // Section B.2.3 states that "the value of Cs_j shall be different from + // the values of Cs_1 through Cs_(j-1)". Since we have previously + // verified that a frame's component identifiers (C_i values in section + // B.2.2) are unique, it suffices to check that the implicit indexes + // into d.comp are unique. + for j := 0; j < i; j++ { + if scan[i].compIndex == scan[j].compIndex { + return FormatError("repeated component selector") + } + } + totalHV += d.comp[compIndex].h * d.comp[compIndex].v + + // The baseline t <= 1 restriction is specified in table B.3. + scan[i].td = d.tmp[2+2*i] >> 4 + if t := scan[i].td; t > maxTh || (d.baseline && t > 1) { + return FormatError("bad Td value") + } + scan[i].ta = d.tmp[2+2*i] & 0x0f + if t := scan[i].ta; t > maxTh || (d.baseline && t > 1) { + return FormatError("bad Ta value") + } + } + // Section B.2.3 states that if there is more than one component then the + // total H*V values in a scan must be <= 10. + if d.nComp > 1 && totalHV > 10 { + return FormatError("total sampling factors too large") + } + + // zigStart and zigEnd are the spectral selection bounds. + // ah and al are the successive approximation high and low values. + // The spec calls these values Ss, Se, Ah and Al. + // + // For progressive JPEGs, these are the two more-or-less independent + // aspects of progression. Spectral selection progression is when not + // all of a block's 64 DCT coefficients are transmitted in one pass. + // For example, three passes could transmit coefficient 0 (the DC + // component), coefficients 1-5, and coefficients 6-63, in zig-zag + // order. Successive approximation is when not all of the bits of a + // band of coefficients are transmitted in one pass. For example, + // three passes could transmit the 6 most significant bits, followed + // by the second-least significant bit, followed by the least + // significant bit. + // + // For sequential JPEGs, these parameters are hard-coded to 0/63/0/0, as + // per table B.3. + zigStart, zigEnd, ah, al := int32(0), int32(blockSize-1), uint32(0), uint32(0) + if d.progressive { + zigStart = int32(d.tmp[1+2*nComp]) + zigEnd = int32(d.tmp[2+2*nComp]) + ah = uint32(d.tmp[3+2*nComp] >> 4) + al = uint32(d.tmp[3+2*nComp] & 0x0f) + if (zigStart == 0 && zigEnd != 0) || zigStart > zigEnd || blockSize <= zigEnd { + return FormatError("bad spectral selection bounds") + } + if zigStart != 0 && nComp != 1 { + return FormatError("progressive AC coefficients for more than one component") + } + if ah != 0 && ah != al+1 { + return FormatError("bad successive approximation values") + } + } + + // mxx and myy are the number of MCUs (Minimum Coded Units) in the image. + h0, v0 := d.comp[0].h, d.comp[0].v // The h and v values from the Y components. + mxx := (d.width + 8*h0 - 1) / (8 * h0) + myy := (d.height + 8*v0 - 1) / (8 * v0) + if d.img1 == nil && d.img3 == nil { + d.makeImg(mxx, myy) + } + if d.progressive { + for i := 0; i < nComp; i++ { + compIndex := scan[i].compIndex + if d.progCoeffs[compIndex] == nil { + d.progCoeffs[compIndex] = make([]block, mxx*myy*d.comp[compIndex].h*d.comp[compIndex].v) + } + } + } + + d.bits = bits{} + mcu, expectedRST := 0, uint8(rst0Marker) + var ( + // b is the decoded coefficients, in natural (not zig-zag) order. + b block + dc [maxComponents]int32 + // bx and by are the location of the current block, in units of 8x8 + // blocks: the third block in the first row has (bx, by) = (2, 0). + bx, by int + blockCount int + ) + for my := 0; my < myy; my++ { + for mx := 0; mx < mxx; mx++ { + for i := 0; i < nComp; i++ { + compIndex := scan[i].compIndex + hi := d.comp[compIndex].h + vi := d.comp[compIndex].v + for j := 0; j < hi*vi; j++ { + // The blocks are traversed one MCU at a time. For 4:2:0 chroma + // subsampling, there are four Y 8x8 blocks in every 16x16 MCU. + // + // For a sequential 32x16 pixel image, the Y blocks visiting order is: + // 0 1 4 5 + // 2 3 6 7 + // + // For progressive images, the interleaved scans (those with nComp > 1) + // are traversed as above, but non-interleaved scans are traversed left + // to right, top to bottom: + // 0 1 2 3 + // 4 5 6 7 + // Only DC scans (zigStart == 0) can be interleaved. AC scans must have + // only one component. + // + // To further complicate matters, for non-interleaved scans, there is no + // data for any blocks that are inside the image at the MCU level but + // outside the image at the pixel level. For example, a 24x16 pixel 4:2:0 + // progressive image consists of two 16x16 MCUs. The interleaved scans + // will process 8 Y blocks: + // 0 1 4 5 + // 2 3 6 7 + // The non-interleaved scans will process only 6 Y blocks: + // 0 1 2 + // 3 4 5 + if nComp != 1 { + bx = hi*mx + j%hi + by = vi*my + j/hi + } else { + q := mxx * hi + bx = blockCount % q + by = blockCount / q + blockCount++ + if bx*8 >= d.width || by*8 >= d.height { + continue + } + } + + // Load the previous partially decoded coefficients, if applicable. + if d.progressive { + b = d.progCoeffs[compIndex][by*mxx*hi+bx] + } else { + b = block{} + } + + if ah != 0 { + if err := d.refine(&b, &d.huff[acTable][scan[i].ta], zigStart, zigEnd, 1<<al); err != nil { + return err + } + } else { + zig := zigStart + if zig == 0 { + zig++ + // Decode the DC coefficient, as specified in section F.2.2.1. + value, err := d.decodeHuffman(&d.huff[dcTable][scan[i].td]) + if err != nil { + return err + } + if value > 16 { + return UnsupportedError("excessive DC component") + } + dcDelta, err := d.receiveExtend(value) + if err != nil { + return err + } + dc[compIndex] += dcDelta + b[0] = dc[compIndex] << al + } + + if zig <= zigEnd && d.eobRun > 0 { + d.eobRun-- + } else { + // Decode the AC coefficients, as specified in section F.2.2.2. + huff := &d.huff[acTable][scan[i].ta] + for ; zig <= zigEnd; zig++ { + value, err := d.decodeHuffman(huff) + if err != nil { + return err + } + val0 := value >> 4 + val1 := value & 0x0f + if val1 != 0 { + zig += int32(val0) + if zig > zigEnd { + break + } + ac, err := d.receiveExtend(val1) + if err != nil { + return err + } + b[unzig[zig]] = ac << al + } else { + if val0 != 0x0f { + d.eobRun = uint16(1 << val0) + if val0 != 0 { + bits, err := d.decodeBits(int32(val0)) + if err != nil { + return err + } + d.eobRun |= uint16(bits) + } + d.eobRun-- + break + } + zig += 0x0f + } + } + } + } + + if d.progressive { + // Save the coefficients. + d.progCoeffs[compIndex][by*mxx*hi+bx] = b + // At this point, we could call reconstructBlock to dequantize and perform the + // inverse DCT, to save early stages of a progressive image to the *image.YCbCr + // buffers (the whole point of progressive encoding), but in Go, the jpeg.Decode + // function does not return until the entire image is decoded, so we "continue" + // here to avoid wasted computation. Instead, reconstructBlock is called on each + // accumulated block by the reconstructProgressiveImage method after all of the + // SOS markers are processed. + continue + } + if err := d.reconstructBlock(&b, bx, by, int(compIndex)); err != nil { + return err + } + } // for j + } // for i + mcu++ + if d.ri > 0 && mcu%d.ri == 0 && mcu < mxx*myy { + // A more sophisticated decoder could use RST[0-7] markers to resynchronize from corrupt input, + // but this one assumes well-formed input, and hence the restart marker follows immediately. + if err := d.readFull(d.tmp[:2]); err != nil { + return err + } + + // Section F.1.2.3 says that "Byte alignment of markers is + // achieved by padding incomplete bytes with 1-bits. If padding + // with 1-bits creates a X’FF’ value, a zero byte is stuffed + // before adding the marker." + // + // Seeing "\xff\x00" here is not spec compliant, as we are not + // expecting an *incomplete* byte (that needed padding). Still, + // some real world encoders (see golang.org/issue/28717) insert + // it, so we accept it and re-try the 2 byte read. + // + // libjpeg issues a warning (but not an error) for this: + // https://github.com/LuaDist/libjpeg/blob/6c0fcb8ddee365e7abc4d332662b06900612e923/jdmarker.c#L1041-L1046 + if d.tmp[0] == 0xff && d.tmp[1] == 0x00 { + if err := d.readFull(d.tmp[:2]); err != nil { + return err + } + } + + if d.tmp[0] != 0xff || d.tmp[1] != expectedRST { + return FormatError("bad RST marker") + } + expectedRST++ + if expectedRST == rst7Marker+1 { + expectedRST = rst0Marker + } + // Reset the Huffman decoder. + d.bits = bits{} + // Reset the DC components, as per section F.2.1.3.1. + dc = [maxComponents]int32{} + // Reset the progressive decoder state, as per section G.1.2.2. + d.eobRun = 0 + } + } // for mx + } // for my + + return nil +} + +// refine decodes a successive approximation refinement block, as specified in +// section G.1.2. +func (d *decoder) refine(b *block, h *huffman, zigStart, zigEnd, delta int32) error { + // Refining a DC component is trivial. + if zigStart == 0 { + if zigEnd != 0 { + panic("unreachable") + } + bit, err := d.decodeBit() + if err != nil { + return err + } + if bit { + b[0] |= delta + } + return nil + } + + // Refining AC components is more complicated; see sections G.1.2.2 and G.1.2.3. + zig := zigStart + if d.eobRun == 0 { + loop: + for ; zig <= zigEnd; zig++ { + z := int32(0) + value, err := d.decodeHuffman(h) + if err != nil { + return err + } + val0 := value >> 4 + val1 := value & 0x0f + + switch val1 { + case 0: + if val0 != 0x0f { + d.eobRun = uint16(1 << val0) + if val0 != 0 { + bits, err := d.decodeBits(int32(val0)) + if err != nil { + return err + } + d.eobRun |= uint16(bits) + } + break loop + } + case 1: + z = delta + bit, err := d.decodeBit() + if err != nil { + return err + } + if !bit { + z = -z + } + default: + return FormatError("unexpected Huffman code") + } + + zig, err = d.refineNonZeroes(b, zig, zigEnd, int32(val0), delta) + if err != nil { + return err + } + if zig > zigEnd { + return FormatError("too many coefficients") + } + if z != 0 { + b[unzig[zig]] = z + } + } + } + if d.eobRun > 0 { + d.eobRun-- + if _, err := d.refineNonZeroes(b, zig, zigEnd, -1, delta); err != nil { + return err + } + } + return nil +} + +// refineNonZeroes refines non-zero entries of b in zig-zag order. If nz >= 0, +// the first nz zero entries are skipped over. +func (d *decoder) refineNonZeroes(b *block, zig, zigEnd, nz, delta int32) (int32, error) { + for ; zig <= zigEnd; zig++ { + u := unzig[zig] + if b[u] == 0 { + if nz == 0 { + break + } + nz-- + continue + } + bit, err := d.decodeBit() + if err != nil { + return 0, err + } + if !bit { + continue + } + if b[u] >= 0 { + b[u] += delta + } else { + b[u] -= delta + } + } + return zig, nil +} + +func (d *decoder) reconstructProgressiveImage() error { + // The h0, mxx, by and bx variables have the same meaning as in the + // processSOS method. + h0 := d.comp[0].h + mxx := (d.width + 8*h0 - 1) / (8 * h0) + for i := 0; i < d.nComp; i++ { + if d.progCoeffs[i] == nil { + continue + } + v := 8 * d.comp[0].v / d.comp[i].v + h := 8 * d.comp[0].h / d.comp[i].h + stride := mxx * d.comp[i].h + for by := 0; by*v < d.height; by++ { + for bx := 0; bx*h < d.width; bx++ { + if err := d.reconstructBlock(&d.progCoeffs[i][by*stride+bx], bx, by, i); err != nil { + return err + } + } + } + } + return nil +} + +// reconstructBlock dequantizes, performs the inverse DCT and stores the block +// to the image. +func (d *decoder) reconstructBlock(b *block, bx, by, compIndex int) error { + qt := &d.quant[d.comp[compIndex].tq] + for zig := 0; zig < blockSize; zig++ { + b[unzig[zig]] *= qt[zig] + } + idct(b) + dst, stride := []byte(nil), 0 + if d.nComp == 1 { + dst, stride = d.img1.Pix[8*(by*d.img1.Stride+bx):], d.img1.Stride + } else { + switch compIndex { + case 0: + dst, stride = d.img3.Y[8*(by*d.img3.YStride+bx):], d.img3.YStride + case 1: + dst, stride = d.img3.Cb[8*(by*d.img3.CStride+bx):], d.img3.CStride + case 2: + dst, stride = d.img3.Cr[8*(by*d.img3.CStride+bx):], d.img3.CStride + case 3: + dst, stride = d.blackPix[8*(by*d.blackStride+bx):], d.blackStride + default: + return UnsupportedError("too many components") + } + } + // Level shift by +128, clip to [0, 255], and write to dst. + for y := 0; y < 8; y++ { + y8 := y * 8 + yStride := y * stride + for x := 0; x < 8; x++ { + c := b[y8+x] + if c < -128 { + c = 0 + } else if c > 127 { + c = 255 + } else { + c += 128 + } + dst[yStride+x] = uint8(c) + } + } + return nil +} diff --git a/src/image/jpeg/writer.go b/src/image/jpeg/writer.go new file mode 100644 index 0000000..a600499 --- /dev/null +++ b/src/image/jpeg/writer.go @@ -0,0 +1,641 @@ +// Copyright 2011 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package jpeg + +import ( + "bufio" + "errors" + "image" + "image/color" + "io" +) + +// min returns the minimum of two integers. +func min(x, y int) int { + if x < y { + return x + } + return y +} + +// div returns a/b rounded to the nearest integer, instead of rounded to zero. +func div(a, b int32) int32 { + if a >= 0 { + return (a + (b >> 1)) / b + } + return -((-a + (b >> 1)) / b) +} + +// bitCount counts the number of bits needed to hold an integer. +var bitCount = [256]byte{ + 0, 1, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4, + 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, + 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, + 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, + 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, + 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, + 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, + 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, + 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, + 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, + 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, + 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, + 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, + 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, + 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, + 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, +} + +type quantIndex int + +const ( + quantIndexLuminance quantIndex = iota + quantIndexChrominance + nQuantIndex +) + +// unscaledQuant are the unscaled quantization tables in zig-zag order. Each +// encoder copies and scales the tables according to its quality parameter. +// The values are derived from section K.1 after converting from natural to +// zig-zag order. +var unscaledQuant = [nQuantIndex][blockSize]byte{ + // Luminance. + { + 16, 11, 12, 14, 12, 10, 16, 14, + 13, 14, 18, 17, 16, 19, 24, 40, + 26, 24, 22, 22, 24, 49, 35, 37, + 29, 40, 58, 51, 61, 60, 57, 51, + 56, 55, 64, 72, 92, 78, 64, 68, + 87, 69, 55, 56, 80, 109, 81, 87, + 95, 98, 103, 104, 103, 62, 77, 113, + 121, 112, 100, 120, 92, 101, 103, 99, + }, + // Chrominance. + { + 17, 18, 18, 24, 21, 24, 47, 26, + 26, 47, 99, 66, 56, 66, 99, 99, + 99, 99, 99, 99, 99, 99, 99, 99, + 99, 99, 99, 99, 99, 99, 99, 99, + 99, 99, 99, 99, 99, 99, 99, 99, + 99, 99, 99, 99, 99, 99, 99, 99, + 99, 99, 99, 99, 99, 99, 99, 99, + 99, 99, 99, 99, 99, 99, 99, 99, + }, +} + +type huffIndex int + +const ( + huffIndexLuminanceDC huffIndex = iota + huffIndexLuminanceAC + huffIndexChrominanceDC + huffIndexChrominanceAC + nHuffIndex +) + +// huffmanSpec specifies a Huffman encoding. +type huffmanSpec struct { + // count[i] is the number of codes of length i bits. + count [16]byte + // value[i] is the decoded value of the i'th codeword. + value []byte +} + +// theHuffmanSpec is the Huffman encoding specifications. +// This encoder uses the same Huffman encoding for all images. +var theHuffmanSpec = [nHuffIndex]huffmanSpec{ + // Luminance DC. + { + [16]byte{0, 1, 5, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0}, + []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11}, + }, + // Luminance AC. + { + [16]byte{0, 2, 1, 3, 3, 2, 4, 3, 5, 5, 4, 4, 0, 0, 1, 125}, + []byte{ + 0x01, 0x02, 0x03, 0x00, 0x04, 0x11, 0x05, 0x12, + 0x21, 0x31, 0x41, 0x06, 0x13, 0x51, 0x61, 0x07, + 0x22, 0x71, 0x14, 0x32, 0x81, 0x91, 0xa1, 0x08, + 0x23, 0x42, 0xb1, 0xc1, 0x15, 0x52, 0xd1, 0xf0, + 0x24, 0x33, 0x62, 0x72, 0x82, 0x09, 0x0a, 0x16, + 0x17, 0x18, 0x19, 0x1a, 0x25, 0x26, 0x27, 0x28, + 0x29, 0x2a, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39, + 0x3a, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48, 0x49, + 0x4a, 0x53, 0x54, 0x55, 0x56, 0x57, 0x58, 0x59, + 0x5a, 0x63, 0x64, 0x65, 0x66, 0x67, 0x68, 0x69, + 0x6a, 0x73, 0x74, 0x75, 0x76, 0x77, 0x78, 0x79, + 0x7a, 0x83, 0x84, 0x85, 0x86, 0x87, 0x88, 0x89, + 0x8a, 0x92, 0x93, 0x94, 0x95, 0x96, 0x97, 0x98, + 0x99, 0x9a, 0xa2, 0xa3, 0xa4, 0xa5, 0xa6, 0xa7, + 0xa8, 0xa9, 0xaa, 0xb2, 0xb3, 0xb4, 0xb5, 0xb6, + 0xb7, 0xb8, 0xb9, 0xba, 0xc2, 0xc3, 0xc4, 0xc5, + 0xc6, 0xc7, 0xc8, 0xc9, 0xca, 0xd2, 0xd3, 0xd4, + 0xd5, 0xd6, 0xd7, 0xd8, 0xd9, 0xda, 0xe1, 0xe2, + 0xe3, 0xe4, 0xe5, 0xe6, 0xe7, 0xe8, 0xe9, 0xea, + 0xf1, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7, 0xf8, + 0xf9, 0xfa, + }, + }, + // Chrominance DC. + { + [16]byte{0, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0}, + []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11}, + }, + // Chrominance AC. + { + [16]byte{0, 2, 1, 2, 4, 4, 3, 4, 7, 5, 4, 4, 0, 1, 2, 119}, + []byte{ + 0x00, 0x01, 0x02, 0x03, 0x11, 0x04, 0x05, 0x21, + 0x31, 0x06, 0x12, 0x41, 0x51, 0x07, 0x61, 0x71, + 0x13, 0x22, 0x32, 0x81, 0x08, 0x14, 0x42, 0x91, + 0xa1, 0xb1, 0xc1, 0x09, 0x23, 0x33, 0x52, 0xf0, + 0x15, 0x62, 0x72, 0xd1, 0x0a, 0x16, 0x24, 0x34, + 0xe1, 0x25, 0xf1, 0x17, 0x18, 0x19, 0x1a, 0x26, + 0x27, 0x28, 0x29, 0x2a, 0x35, 0x36, 0x37, 0x38, + 0x39, 0x3a, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48, + 0x49, 0x4a, 0x53, 0x54, 0x55, 0x56, 0x57, 0x58, + 0x59, 0x5a, 0x63, 0x64, 0x65, 0x66, 0x67, 0x68, + 0x69, 0x6a, 0x73, 0x74, 0x75, 0x76, 0x77, 0x78, + 0x79, 0x7a, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87, + 0x88, 0x89, 0x8a, 0x92, 0x93, 0x94, 0x95, 0x96, + 0x97, 0x98, 0x99, 0x9a, 0xa2, 0xa3, 0xa4, 0xa5, + 0xa6, 0xa7, 0xa8, 0xa9, 0xaa, 0xb2, 0xb3, 0xb4, + 0xb5, 0xb6, 0xb7, 0xb8, 0xb9, 0xba, 0xc2, 0xc3, + 0xc4, 0xc5, 0xc6, 0xc7, 0xc8, 0xc9, 0xca, 0xd2, + 0xd3, 0xd4, 0xd5, 0xd6, 0xd7, 0xd8, 0xd9, 0xda, + 0xe2, 0xe3, 0xe4, 0xe5, 0xe6, 0xe7, 0xe8, 0xe9, + 0xea, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7, 0xf8, + 0xf9, 0xfa, + }, + }, +} + +// huffmanLUT is a compiled look-up table representation of a huffmanSpec. +// Each value maps to a uint32 of which the 8 most significant bits hold the +// codeword size in bits and the 24 least significant bits hold the codeword. +// The maximum codeword size is 16 bits. +type huffmanLUT []uint32 + +func (h *huffmanLUT) init(s huffmanSpec) { + maxValue := 0 + for _, v := range s.value { + if int(v) > maxValue { + maxValue = int(v) + } + } + *h = make([]uint32, maxValue+1) + code, k := uint32(0), 0 + for i := 0; i < len(s.count); i++ { + nBits := uint32(i+1) << 24 + for j := uint8(0); j < s.count[i]; j++ { + (*h)[s.value[k]] = nBits | code + code++ + k++ + } + code <<= 1 + } +} + +// theHuffmanLUT are compiled representations of theHuffmanSpec. +var theHuffmanLUT [4]huffmanLUT + +func init() { + for i, s := range theHuffmanSpec { + theHuffmanLUT[i].init(s) + } +} + +// writer is a buffered writer. +type writer interface { + Flush() error + io.Writer + io.ByteWriter +} + +// encoder encodes an image to the JPEG format. +type encoder struct { + // w is the writer to write to. err is the first error encountered during + // writing. All attempted writes after the first error become no-ops. + w writer + err error + // buf is a scratch buffer. + buf [16]byte + // bits and nBits are accumulated bits to write to w. + bits, nBits uint32 + // quant is the scaled quantization tables, in zig-zag order. + quant [nQuantIndex][blockSize]byte +} + +func (e *encoder) flush() { + if e.err != nil { + return + } + e.err = e.w.Flush() +} + +func (e *encoder) write(p []byte) { + if e.err != nil { + return + } + _, e.err = e.w.Write(p) +} + +func (e *encoder) writeByte(b byte) { + if e.err != nil { + return + } + e.err = e.w.WriteByte(b) +} + +// emit emits the least significant nBits bits of bits to the bit-stream. +// The precondition is bits < 1<<nBits && nBits <= 16. +func (e *encoder) emit(bits, nBits uint32) { + nBits += e.nBits + bits <<= 32 - nBits + bits |= e.bits + for nBits >= 8 { + b := uint8(bits >> 24) + e.writeByte(b) + if b == 0xff { + e.writeByte(0x00) + } + bits <<= 8 + nBits -= 8 + } + e.bits, e.nBits = bits, nBits +} + +// emitHuff emits the given value with the given Huffman encoder. +func (e *encoder) emitHuff(h huffIndex, value int32) { + x := theHuffmanLUT[h][value] + e.emit(x&(1<<24-1), x>>24) +} + +// emitHuffRLE emits a run of runLength copies of value encoded with the given +// Huffman encoder. +func (e *encoder) emitHuffRLE(h huffIndex, runLength, value int32) { + a, b := value, value + if a < 0 { + a, b = -value, value-1 + } + var nBits uint32 + if a < 0x100 { + nBits = uint32(bitCount[a]) + } else { + nBits = 8 + uint32(bitCount[a>>8]) + } + e.emitHuff(h, runLength<<4|int32(nBits)) + if nBits > 0 { + e.emit(uint32(b)&(1<<nBits-1), nBits) + } +} + +// writeMarkerHeader writes the header for a marker with the given length. +func (e *encoder) writeMarkerHeader(marker uint8, markerlen int) { + e.buf[0] = 0xff + e.buf[1] = marker + e.buf[2] = uint8(markerlen >> 8) + e.buf[3] = uint8(markerlen & 0xff) + e.write(e.buf[:4]) +} + +// writeDQT writes the Define Quantization Table marker. +func (e *encoder) writeDQT() { + const markerlen = 2 + int(nQuantIndex)*(1+blockSize) + e.writeMarkerHeader(dqtMarker, markerlen) + for i := range e.quant { + e.writeByte(uint8(i)) + e.write(e.quant[i][:]) + } +} + +// writeSOF0 writes the Start Of Frame (Baseline Sequential) marker. +func (e *encoder) writeSOF0(size image.Point, nComponent int) { + markerlen := 8 + 3*nComponent + e.writeMarkerHeader(sof0Marker, markerlen) + e.buf[0] = 8 // 8-bit color. + e.buf[1] = uint8(size.Y >> 8) + e.buf[2] = uint8(size.Y & 0xff) + e.buf[3] = uint8(size.X >> 8) + e.buf[4] = uint8(size.X & 0xff) + e.buf[5] = uint8(nComponent) + if nComponent == 1 { + e.buf[6] = 1 + // No subsampling for grayscale image. + e.buf[7] = 0x11 + e.buf[8] = 0x00 + } else { + for i := 0; i < nComponent; i++ { + e.buf[3*i+6] = uint8(i + 1) + // We use 4:2:0 chroma subsampling. + e.buf[3*i+7] = "\x22\x11\x11"[i] + e.buf[3*i+8] = "\x00\x01\x01"[i] + } + } + e.write(e.buf[:3*(nComponent-1)+9]) +} + +// writeDHT writes the Define Huffman Table marker. +func (e *encoder) writeDHT(nComponent int) { + markerlen := 2 + specs := theHuffmanSpec[:] + if nComponent == 1 { + // Drop the Chrominance tables. + specs = specs[:2] + } + for _, s := range specs { + markerlen += 1 + 16 + len(s.value) + } + e.writeMarkerHeader(dhtMarker, markerlen) + for i, s := range specs { + e.writeByte("\x00\x10\x01\x11"[i]) + e.write(s.count[:]) + e.write(s.value) + } +} + +// writeBlock writes a block of pixel data using the given quantization table, +// returning the post-quantized DC value of the DCT-transformed block. b is in +// natural (not zig-zag) order. +func (e *encoder) writeBlock(b *block, q quantIndex, prevDC int32) int32 { + fdct(b) + // Emit the DC delta. + dc := div(b[0], 8*int32(e.quant[q][0])) + e.emitHuffRLE(huffIndex(2*q+0), 0, dc-prevDC) + // Emit the AC components. + h, runLength := huffIndex(2*q+1), int32(0) + for zig := 1; zig < blockSize; zig++ { + ac := div(b[unzig[zig]], 8*int32(e.quant[q][zig])) + if ac == 0 { + runLength++ + } else { + for runLength > 15 { + e.emitHuff(h, 0xf0) + runLength -= 16 + } + e.emitHuffRLE(h, runLength, ac) + runLength = 0 + } + } + if runLength > 0 { + e.emitHuff(h, 0x00) + } + return dc +} + +// toYCbCr converts the 8x8 region of m whose top-left corner is p to its +// YCbCr values. +func toYCbCr(m image.Image, p image.Point, yBlock, cbBlock, crBlock *block) { + b := m.Bounds() + xmax := b.Max.X - 1 + ymax := b.Max.Y - 1 + for j := 0; j < 8; j++ { + for i := 0; i < 8; i++ { + r, g, b, _ := m.At(min(p.X+i, xmax), min(p.Y+j, ymax)).RGBA() + yy, cb, cr := color.RGBToYCbCr(uint8(r>>8), uint8(g>>8), uint8(b>>8)) + yBlock[8*j+i] = int32(yy) + cbBlock[8*j+i] = int32(cb) + crBlock[8*j+i] = int32(cr) + } + } +} + +// grayToY stores the 8x8 region of m whose top-left corner is p in yBlock. +func grayToY(m *image.Gray, p image.Point, yBlock *block) { + b := m.Bounds() + xmax := b.Max.X - 1 + ymax := b.Max.Y - 1 + pix := m.Pix + for j := 0; j < 8; j++ { + for i := 0; i < 8; i++ { + idx := m.PixOffset(min(p.X+i, xmax), min(p.Y+j, ymax)) + yBlock[8*j+i] = int32(pix[idx]) + } + } +} + +// rgbaToYCbCr is a specialized version of toYCbCr for image.RGBA images. +func rgbaToYCbCr(m *image.RGBA, p image.Point, yBlock, cbBlock, crBlock *block) { + b := m.Bounds() + xmax := b.Max.X - 1 + ymax := b.Max.Y - 1 + for j := 0; j < 8; j++ { + sj := p.Y + j + if sj > ymax { + sj = ymax + } + offset := (sj-b.Min.Y)*m.Stride - b.Min.X*4 + for i := 0; i < 8; i++ { + sx := p.X + i + if sx > xmax { + sx = xmax + } + pix := m.Pix[offset+sx*4:] + yy, cb, cr := color.RGBToYCbCr(pix[0], pix[1], pix[2]) + yBlock[8*j+i] = int32(yy) + cbBlock[8*j+i] = int32(cb) + crBlock[8*j+i] = int32(cr) + } + } +} + +// yCbCrToYCbCr is a specialized version of toYCbCr for image.YCbCr images. +func yCbCrToYCbCr(m *image.YCbCr, p image.Point, yBlock, cbBlock, crBlock *block) { + b := m.Bounds() + xmax := b.Max.X - 1 + ymax := b.Max.Y - 1 + for j := 0; j < 8; j++ { + sy := p.Y + j + if sy > ymax { + sy = ymax + } + for i := 0; i < 8; i++ { + sx := p.X + i + if sx > xmax { + sx = xmax + } + yi := m.YOffset(sx, sy) + ci := m.COffset(sx, sy) + yBlock[8*j+i] = int32(m.Y[yi]) + cbBlock[8*j+i] = int32(m.Cb[ci]) + crBlock[8*j+i] = int32(m.Cr[ci]) + } + } +} + +// scale scales the 16x16 region represented by the 4 src blocks to the 8x8 +// dst block. +func scale(dst *block, src *[4]block) { + for i := 0; i < 4; i++ { + dstOff := (i&2)<<4 | (i&1)<<2 + for y := 0; y < 4; y++ { + for x := 0; x < 4; x++ { + j := 16*y + 2*x + sum := src[i][j] + src[i][j+1] + src[i][j+8] + src[i][j+9] + dst[8*y+x+dstOff] = (sum + 2) >> 2 + } + } + } +} + +// sosHeaderY is the SOS marker "\xff\xda" followed by 8 bytes: +// - the marker length "\x00\x08", +// - the number of components "\x01", +// - component 1 uses DC table 0 and AC table 0 "\x01\x00", +// - the bytes "\x00\x3f\x00". Section B.2.3 of the spec says that for +// sequential DCTs, those bytes (8-bit Ss, 8-bit Se, 4-bit Ah, 4-bit Al) +// should be 0x00, 0x3f, 0x00<<4 | 0x00. +var sosHeaderY = []byte{ + 0xff, 0xda, 0x00, 0x08, 0x01, 0x01, 0x00, 0x00, 0x3f, 0x00, +} + +// sosHeaderYCbCr is the SOS marker "\xff\xda" followed by 12 bytes: +// - the marker length "\x00\x0c", +// - the number of components "\x03", +// - component 1 uses DC table 0 and AC table 0 "\x01\x00", +// - component 2 uses DC table 1 and AC table 1 "\x02\x11", +// - component 3 uses DC table 1 and AC table 1 "\x03\x11", +// - the bytes "\x00\x3f\x00". Section B.2.3 of the spec says that for +// sequential DCTs, those bytes (8-bit Ss, 8-bit Se, 4-bit Ah, 4-bit Al) +// should be 0x00, 0x3f, 0x00<<4 | 0x00. +var sosHeaderYCbCr = []byte{ + 0xff, 0xda, 0x00, 0x0c, 0x03, 0x01, 0x00, 0x02, + 0x11, 0x03, 0x11, 0x00, 0x3f, 0x00, +} + +// writeSOS writes the StartOfScan marker. +func (e *encoder) writeSOS(m image.Image) { + switch m.(type) { + case *image.Gray: + e.write(sosHeaderY) + default: + e.write(sosHeaderYCbCr) + } + var ( + // Scratch buffers to hold the YCbCr values. + // The blocks are in natural (not zig-zag) order. + b block + cb, cr [4]block + // DC components are delta-encoded. + prevDCY, prevDCCb, prevDCCr int32 + ) + bounds := m.Bounds() + switch m := m.(type) { + // TODO(wathiede): switch on m.ColorModel() instead of type. + case *image.Gray: + for y := bounds.Min.Y; y < bounds.Max.Y; y += 8 { + for x := bounds.Min.X; x < bounds.Max.X; x += 8 { + p := image.Pt(x, y) + grayToY(m, p, &b) + prevDCY = e.writeBlock(&b, 0, prevDCY) + } + } + default: + rgba, _ := m.(*image.RGBA) + ycbcr, _ := m.(*image.YCbCr) + for y := bounds.Min.Y; y < bounds.Max.Y; y += 16 { + for x := bounds.Min.X; x < bounds.Max.X; x += 16 { + for i := 0; i < 4; i++ { + xOff := (i & 1) * 8 + yOff := (i & 2) * 4 + p := image.Pt(x+xOff, y+yOff) + if rgba != nil { + rgbaToYCbCr(rgba, p, &b, &cb[i], &cr[i]) + } else if ycbcr != nil { + yCbCrToYCbCr(ycbcr, p, &b, &cb[i], &cr[i]) + } else { + toYCbCr(m, p, &b, &cb[i], &cr[i]) + } + prevDCY = e.writeBlock(&b, 0, prevDCY) + } + scale(&b, &cb) + prevDCCb = e.writeBlock(&b, 1, prevDCCb) + scale(&b, &cr) + prevDCCr = e.writeBlock(&b, 1, prevDCCr) + } + } + } + // Pad the last byte with 1's. + e.emit(0x7f, 7) +} + +// DefaultQuality is the default quality encoding parameter. +const DefaultQuality = 75 + +// Options are the encoding parameters. +// Quality ranges from 1 to 100 inclusive, higher is better. +type Options struct { + Quality int +} + +// Encode writes the Image m to w in JPEG 4:2:0 baseline format with the given +// options. Default parameters are used if a nil *Options is passed. +func Encode(w io.Writer, m image.Image, o *Options) error { + b := m.Bounds() + if b.Dx() >= 1<<16 || b.Dy() >= 1<<16 { + return errors.New("jpeg: image is too large to encode") + } + var e encoder + if ww, ok := w.(writer); ok { + e.w = ww + } else { + e.w = bufio.NewWriter(w) + } + // Clip quality to [1, 100]. + quality := DefaultQuality + if o != nil { + quality = o.Quality + if quality < 1 { + quality = 1 + } else if quality > 100 { + quality = 100 + } + } + // Convert from a quality rating to a scaling factor. + var scale int + if quality < 50 { + scale = 5000 / quality + } else { + scale = 200 - quality*2 + } + // Initialize the quantization tables. + for i := range e.quant { + for j := range e.quant[i] { + x := int(unscaledQuant[i][j]) + x = (x*scale + 50) / 100 + if x < 1 { + x = 1 + } else if x > 255 { + x = 255 + } + e.quant[i][j] = uint8(x) + } + } + // Compute number of components based on input image type. + nComponent := 3 + switch m.(type) { + // TODO(wathiede): switch on m.ColorModel() instead of type. + case *image.Gray: + nComponent = 1 + } + // Write the Start Of Image marker. + e.buf[0] = 0xff + e.buf[1] = 0xd8 + e.write(e.buf[:2]) + // Write the quantization tables. + e.writeDQT() + // Write the image dimensions. + e.writeSOF0(b.Size(), nComponent) + // Write the Huffman tables. + e.writeDHT(nComponent) + // Write the image data. + e.writeSOS(m) + // Write the End Of Image marker. + e.buf[0] = 0xff + e.buf[1] = 0xd9 + e.write(e.buf[:2]) + e.flush() + return e.err +} diff --git a/src/image/jpeg/writer_test.go b/src/image/jpeg/writer_test.go new file mode 100644 index 0000000..abd5e32 --- /dev/null +++ b/src/image/jpeg/writer_test.go @@ -0,0 +1,288 @@ +// Copyright 2011 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package jpeg + +import ( + "bytes" + "fmt" + "image" + "image/color" + "image/png" + "io" + "math/rand" + "os" + "testing" +) + +// zigzag maps from the natural ordering to the zig-zag ordering. For example, +// zigzag[0*8 + 3] is the zig-zag sequence number of the element in the fourth +// column and first row. +var zigzag = [blockSize]int{ + 0, 1, 5, 6, 14, 15, 27, 28, + 2, 4, 7, 13, 16, 26, 29, 42, + 3, 8, 12, 17, 25, 30, 41, 43, + 9, 11, 18, 24, 31, 40, 44, 53, + 10, 19, 23, 32, 39, 45, 52, 54, + 20, 22, 33, 38, 46, 51, 55, 60, + 21, 34, 37, 47, 50, 56, 59, 61, + 35, 36, 48, 49, 57, 58, 62, 63, +} + +func TestZigUnzig(t *testing.T) { + for i := 0; i < blockSize; i++ { + if unzig[zigzag[i]] != i { + t.Errorf("unzig[zigzag[%d]] == %d", i, unzig[zigzag[i]]) + } + if zigzag[unzig[i]] != i { + t.Errorf("zigzag[unzig[%d]] == %d", i, zigzag[unzig[i]]) + } + } +} + +// unscaledQuantInNaturalOrder are the unscaled quantization tables in +// natural (not zig-zag) order, as specified in section K.1. +var unscaledQuantInNaturalOrder = [nQuantIndex][blockSize]byte{ + // Luminance. + { + 16, 11, 10, 16, 24, 40, 51, 61, + 12, 12, 14, 19, 26, 58, 60, 55, + 14, 13, 16, 24, 40, 57, 69, 56, + 14, 17, 22, 29, 51, 87, 80, 62, + 18, 22, 37, 56, 68, 109, 103, 77, + 24, 35, 55, 64, 81, 104, 113, 92, + 49, 64, 78, 87, 103, 121, 120, 101, + 72, 92, 95, 98, 112, 100, 103, 99, + }, + // Chrominance. + { + 17, 18, 24, 47, 99, 99, 99, 99, + 18, 21, 26, 66, 99, 99, 99, 99, + 24, 26, 56, 99, 99, 99, 99, 99, + 47, 66, 99, 99, 99, 99, 99, 99, + 99, 99, 99, 99, 99, 99, 99, 99, + 99, 99, 99, 99, 99, 99, 99, 99, + 99, 99, 99, 99, 99, 99, 99, 99, + 99, 99, 99, 99, 99, 99, 99, 99, + }, +} + +func TestUnscaledQuant(t *testing.T) { + bad := false + for i := quantIndex(0); i < nQuantIndex; i++ { + for zig := 0; zig < blockSize; zig++ { + got := unscaledQuant[i][zig] + want := unscaledQuantInNaturalOrder[i][unzig[zig]] + if got != want { + t.Errorf("i=%d, zig=%d: got %d, want %d", i, zig, got, want) + bad = true + } + } + } + if bad { + names := [nQuantIndex]string{"Luminance", "Chrominance"} + buf := &bytes.Buffer{} + for i, name := range names { + fmt.Fprintf(buf, "// %s.\n{\n", name) + for zig := 0; zig < blockSize; zig++ { + fmt.Fprintf(buf, "%d, ", unscaledQuantInNaturalOrder[i][unzig[zig]]) + if zig%8 == 7 { + buf.WriteString("\n") + } + } + buf.WriteString("},\n") + } + t.Logf("expected unscaledQuant values:\n%s", buf.String()) + } +} + +var testCase = []struct { + filename string + quality int + tolerance int64 +}{ + {"../testdata/video-001.png", 1, 24 << 8}, + {"../testdata/video-001.png", 20, 12 << 8}, + {"../testdata/video-001.png", 60, 8 << 8}, + {"../testdata/video-001.png", 80, 6 << 8}, + {"../testdata/video-001.png", 90, 4 << 8}, + {"../testdata/video-001.png", 100, 2 << 8}, +} + +func delta(u0, u1 uint32) int64 { + d := int64(u0) - int64(u1) + if d < 0 { + return -d + } + return d +} + +func readPng(filename string) (image.Image, error) { + f, err := os.Open(filename) + if err != nil { + return nil, err + } + defer f.Close() + return png.Decode(f) +} + +func TestWriter(t *testing.T) { + for _, tc := range testCase { + // Read the image. + m0, err := readPng(tc.filename) + if err != nil { + t.Error(tc.filename, err) + continue + } + // Encode that image as JPEG. + var buf bytes.Buffer + err = Encode(&buf, m0, &Options{Quality: tc.quality}) + if err != nil { + t.Error(tc.filename, err) + continue + } + // Decode that JPEG. + m1, err := Decode(&buf) + if err != nil { + t.Error(tc.filename, err) + continue + } + if m0.Bounds() != m1.Bounds() { + t.Errorf("%s, bounds differ: %v and %v", tc.filename, m0.Bounds(), m1.Bounds()) + continue + } + // Compare the average delta to the tolerance level. + if averageDelta(m0, m1) > tc.tolerance { + t.Errorf("%s, quality=%d: average delta is too high", tc.filename, tc.quality) + continue + } + } +} + +// TestWriteGrayscale tests that a grayscale images survives a round-trip +// through encode/decode cycle. +func TestWriteGrayscale(t *testing.T) { + m0 := image.NewGray(image.Rect(0, 0, 32, 32)) + for i := range m0.Pix { + m0.Pix[i] = uint8(i) + } + var buf bytes.Buffer + if err := Encode(&buf, m0, nil); err != nil { + t.Fatal(err) + } + m1, err := Decode(&buf) + if err != nil { + t.Fatal(err) + } + if m0.Bounds() != m1.Bounds() { + t.Fatalf("bounds differ: %v and %v", m0.Bounds(), m1.Bounds()) + } + if _, ok := m1.(*image.Gray); !ok { + t.Errorf("got %T, want *image.Gray", m1) + } + // Compare the average delta to the tolerance level. + want := int64(2 << 8) + if got := averageDelta(m0, m1); got > want { + t.Errorf("average delta too high; got %d, want <= %d", got, want) + } +} + +// averageDelta returns the average delta in RGB space. The two images must +// have the same bounds. +func averageDelta(m0, m1 image.Image) int64 { + b := m0.Bounds() + var sum, n int64 + for y := b.Min.Y; y < b.Max.Y; y++ { + for x := b.Min.X; x < b.Max.X; x++ { + c0 := m0.At(x, y) + c1 := m1.At(x, y) + r0, g0, b0, _ := c0.RGBA() + r1, g1, b1, _ := c1.RGBA() + sum += delta(r0, r1) + sum += delta(g0, g1) + sum += delta(b0, b1) + n += 3 + } + } + return sum / n +} + +func TestEncodeYCbCr(t *testing.T) { + bo := image.Rect(0, 0, 640, 480) + imgRGBA := image.NewRGBA(bo) + // Must use 444 subsampling to avoid lossy RGBA to YCbCr conversion. + imgYCbCr := image.NewYCbCr(bo, image.YCbCrSubsampleRatio444) + rnd := rand.New(rand.NewSource(123)) + // Create identical rgba and ycbcr images. + for y := bo.Min.Y; y < bo.Max.Y; y++ { + for x := bo.Min.X; x < bo.Max.X; x++ { + col := color.RGBA{ + uint8(rnd.Intn(256)), + uint8(rnd.Intn(256)), + uint8(rnd.Intn(256)), + 255, + } + imgRGBA.SetRGBA(x, y, col) + yo := imgYCbCr.YOffset(x, y) + co := imgYCbCr.COffset(x, y) + cy, ccr, ccb := color.RGBToYCbCr(col.R, col.G, col.B) + imgYCbCr.Y[yo] = cy + imgYCbCr.Cb[co] = ccr + imgYCbCr.Cr[co] = ccb + } + } + + // Now check that both images are identical after an encode. + var bufRGBA, bufYCbCr bytes.Buffer + Encode(&bufRGBA, imgRGBA, nil) + Encode(&bufYCbCr, imgYCbCr, nil) + if !bytes.Equal(bufRGBA.Bytes(), bufYCbCr.Bytes()) { + t.Errorf("RGBA and YCbCr encoded bytes differ") + } +} + +func BenchmarkEncodeRGBA(b *testing.B) { + img := image.NewRGBA(image.Rect(0, 0, 640, 480)) + bo := img.Bounds() + rnd := rand.New(rand.NewSource(123)) + for y := bo.Min.Y; y < bo.Max.Y; y++ { + for x := bo.Min.X; x < bo.Max.X; x++ { + img.SetRGBA(x, y, color.RGBA{ + uint8(rnd.Intn(256)), + uint8(rnd.Intn(256)), + uint8(rnd.Intn(256)), + 255, + }) + } + } + b.SetBytes(640 * 480 * 4) + b.ReportAllocs() + b.ResetTimer() + options := &Options{Quality: 90} + for i := 0; i < b.N; i++ { + Encode(io.Discard, img, options) + } +} + +func BenchmarkEncodeYCbCr(b *testing.B) { + img := image.NewYCbCr(image.Rect(0, 0, 640, 480), image.YCbCrSubsampleRatio420) + bo := img.Bounds() + rnd := rand.New(rand.NewSource(123)) + for y := bo.Min.Y; y < bo.Max.Y; y++ { + for x := bo.Min.X; x < bo.Max.X; x++ { + cy := img.YOffset(x, y) + ci := img.COffset(x, y) + img.Y[cy] = uint8(rnd.Intn(256)) + img.Cb[ci] = uint8(rnd.Intn(256)) + img.Cr[ci] = uint8(rnd.Intn(256)) + } + } + b.SetBytes(640 * 480 * 3) + b.ReportAllocs() + b.ResetTimer() + options := &Options{Quality: 90} + for i := 0; i < b.N; i++ { + Encode(io.Discard, img, options) + } +} |