Adding upstream version 1.21.8.upstream/1.21.8

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 523 insertions, 0 deletions

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
+}