From ccd992355df7192993c666236047820244914598 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Tue, 16 Apr 2024 21:19:13 +0200 Subject: Adding upstream version 1.21.8. Signed-off-by: Daniel Baumann --- src/image/jpeg/scan.go | 523 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 523 insertions(+) create mode 100644 src/image/jpeg/scan.go (limited to 'src/image/jpeg/scan.go') 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< 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 +} -- cgit v1.2.3