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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-16 19:23:18 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-16 19:23:18 +0000 |
commit | 43a123c1ae6613b3efeed291fa552ecd909d3acf (patch) | |
tree | fd92518b7024bc74031f78a1cf9e454b65e73665 /src/image/ycbcr.go | |
parent | Initial commit. (diff) | |
download | golang-1.20-43a123c1ae6613b3efeed291fa552ecd909d3acf.tar.xz golang-1.20-43a123c1ae6613b3efeed291fa552ecd909d3acf.zip |
Adding upstream version 1.20.14.upstream/1.20.14upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'src/image/ycbcr.go')
-rw-r--r-- | src/image/ycbcr.go | 329 |
1 files changed, 329 insertions, 0 deletions
diff --git a/src/image/ycbcr.go b/src/image/ycbcr.go new file mode 100644 index 0000000..78f5ebe --- /dev/null +++ b/src/image/ycbcr.go @@ -0,0 +1,329 @@ +// 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 image + +import ( + "image/color" +) + +// YCbCrSubsampleRatio is the chroma subsample ratio used in a YCbCr image. +type YCbCrSubsampleRatio int + +const ( + YCbCrSubsampleRatio444 YCbCrSubsampleRatio = iota + YCbCrSubsampleRatio422 + YCbCrSubsampleRatio420 + YCbCrSubsampleRatio440 + YCbCrSubsampleRatio411 + YCbCrSubsampleRatio410 +) + +func (s YCbCrSubsampleRatio) String() string { + switch s { + case YCbCrSubsampleRatio444: + return "YCbCrSubsampleRatio444" + case YCbCrSubsampleRatio422: + return "YCbCrSubsampleRatio422" + case YCbCrSubsampleRatio420: + return "YCbCrSubsampleRatio420" + case YCbCrSubsampleRatio440: + return "YCbCrSubsampleRatio440" + case YCbCrSubsampleRatio411: + return "YCbCrSubsampleRatio411" + case YCbCrSubsampleRatio410: + return "YCbCrSubsampleRatio410" + } + return "YCbCrSubsampleRatioUnknown" +} + +// YCbCr is an in-memory image of Y'CbCr colors. There is one Y sample per +// pixel, but each Cb and Cr sample can span one or more pixels. +// YStride is the Y slice index delta between vertically adjacent pixels. +// CStride is the Cb and Cr slice index delta between vertically adjacent pixels +// that map to separate chroma samples. +// It is not an absolute requirement, but YStride and len(Y) are typically +// multiples of 8, and: +// +// For 4:4:4, CStride == YStride/1 && len(Cb) == len(Cr) == len(Y)/1. +// For 4:2:2, CStride == YStride/2 && len(Cb) == len(Cr) == len(Y)/2. +// For 4:2:0, CStride == YStride/2 && len(Cb) == len(Cr) == len(Y)/4. +// For 4:4:0, CStride == YStride/1 && len(Cb) == len(Cr) == len(Y)/2. +// For 4:1:1, CStride == YStride/4 && len(Cb) == len(Cr) == len(Y)/4. +// For 4:1:0, CStride == YStride/4 && len(Cb) == len(Cr) == len(Y)/8. +type YCbCr struct { + Y, Cb, Cr []uint8 + YStride int + CStride int + SubsampleRatio YCbCrSubsampleRatio + Rect Rectangle +} + +func (p *YCbCr) ColorModel() color.Model { + return color.YCbCrModel +} + +func (p *YCbCr) Bounds() Rectangle { + return p.Rect +} + +func (p *YCbCr) At(x, y int) color.Color { + return p.YCbCrAt(x, y) +} + +func (p *YCbCr) RGBA64At(x, y int) color.RGBA64 { + r, g, b, a := p.YCbCrAt(x, y).RGBA() + return color.RGBA64{uint16(r), uint16(g), uint16(b), uint16(a)} +} + +func (p *YCbCr) YCbCrAt(x, y int) color.YCbCr { + if !(Point{x, y}.In(p.Rect)) { + return color.YCbCr{} + } + yi := p.YOffset(x, y) + ci := p.COffset(x, y) + return color.YCbCr{ + p.Y[yi], + p.Cb[ci], + p.Cr[ci], + } +} + +// YOffset returns the index of the first element of Y that corresponds to +// the pixel at (x, y). +func (p *YCbCr) YOffset(x, y int) int { + return (y-p.Rect.Min.Y)*p.YStride + (x - p.Rect.Min.X) +} + +// COffset returns the index of the first element of Cb or Cr that corresponds +// to the pixel at (x, y). +func (p *YCbCr) COffset(x, y int) int { + switch p.SubsampleRatio { + case YCbCrSubsampleRatio422: + return (y-p.Rect.Min.Y)*p.CStride + (x/2 - p.Rect.Min.X/2) + case YCbCrSubsampleRatio420: + return (y/2-p.Rect.Min.Y/2)*p.CStride + (x/2 - p.Rect.Min.X/2) + case YCbCrSubsampleRatio440: + return (y/2-p.Rect.Min.Y/2)*p.CStride + (x - p.Rect.Min.X) + case YCbCrSubsampleRatio411: + return (y-p.Rect.Min.Y)*p.CStride + (x/4 - p.Rect.Min.X/4) + case YCbCrSubsampleRatio410: + return (y/2-p.Rect.Min.Y/2)*p.CStride + (x/4 - p.Rect.Min.X/4) + } + // Default to 4:4:4 subsampling. + return (y-p.Rect.Min.Y)*p.CStride + (x - p.Rect.Min.X) +} + +// SubImage returns an image representing the portion of the image p visible +// through r. The returned value shares pixels with the original image. +func (p *YCbCr) SubImage(r Rectangle) Image { + r = r.Intersect(p.Rect) + // If r1 and r2 are Rectangles, r1.Intersect(r2) is not guaranteed to be inside + // either r1 or r2 if the intersection is empty. Without explicitly checking for + // this, the Pix[i:] expression below can panic. + if r.Empty() { + return &YCbCr{ + SubsampleRatio: p.SubsampleRatio, + } + } + yi := p.YOffset(r.Min.X, r.Min.Y) + ci := p.COffset(r.Min.X, r.Min.Y) + return &YCbCr{ + Y: p.Y[yi:], + Cb: p.Cb[ci:], + Cr: p.Cr[ci:], + SubsampleRatio: p.SubsampleRatio, + YStride: p.YStride, + CStride: p.CStride, + Rect: r, + } +} + +func (p *YCbCr) Opaque() bool { + return true +} + +func yCbCrSize(r Rectangle, subsampleRatio YCbCrSubsampleRatio) (w, h, cw, ch int) { + w, h = r.Dx(), r.Dy() + switch subsampleRatio { + case YCbCrSubsampleRatio422: + cw = (r.Max.X+1)/2 - r.Min.X/2 + ch = h + case YCbCrSubsampleRatio420: + cw = (r.Max.X+1)/2 - r.Min.X/2 + ch = (r.Max.Y+1)/2 - r.Min.Y/2 + case YCbCrSubsampleRatio440: + cw = w + ch = (r.Max.Y+1)/2 - r.Min.Y/2 + case YCbCrSubsampleRatio411: + cw = (r.Max.X+3)/4 - r.Min.X/4 + ch = h + case YCbCrSubsampleRatio410: + cw = (r.Max.X+3)/4 - r.Min.X/4 + ch = (r.Max.Y+1)/2 - r.Min.Y/2 + default: + // Default to 4:4:4 subsampling. + cw = w + ch = h + } + return +} + +// NewYCbCr returns a new YCbCr image with the given bounds and subsample +// ratio. +func NewYCbCr(r Rectangle, subsampleRatio YCbCrSubsampleRatio) *YCbCr { + w, h, cw, ch := yCbCrSize(r, subsampleRatio) + + // totalLength should be the same as i2, below, for a valid Rectangle r. + totalLength := add2NonNeg( + mul3NonNeg(1, w, h), + mul3NonNeg(2, cw, ch), + ) + if totalLength < 0 { + panic("image: NewYCbCr Rectangle has huge or negative dimensions") + } + + i0 := w*h + 0*cw*ch + i1 := w*h + 1*cw*ch + i2 := w*h + 2*cw*ch + b := make([]byte, i2) + return &YCbCr{ + Y: b[:i0:i0], + Cb: b[i0:i1:i1], + Cr: b[i1:i2:i2], + SubsampleRatio: subsampleRatio, + YStride: w, + CStride: cw, + Rect: r, + } +} + +// NYCbCrA is an in-memory image of non-alpha-premultiplied Y'CbCr-with-alpha +// colors. A and AStride are analogous to the Y and YStride fields of the +// embedded YCbCr. +type NYCbCrA struct { + YCbCr + A []uint8 + AStride int +} + +func (p *NYCbCrA) ColorModel() color.Model { + return color.NYCbCrAModel +} + +func (p *NYCbCrA) At(x, y int) color.Color { + return p.NYCbCrAAt(x, y) +} + +func (p *NYCbCrA) RGBA64At(x, y int) color.RGBA64 { + r, g, b, a := p.NYCbCrAAt(x, y).RGBA() + return color.RGBA64{uint16(r), uint16(g), uint16(b), uint16(a)} +} + +func (p *NYCbCrA) NYCbCrAAt(x, y int) color.NYCbCrA { + if !(Point{X: x, Y: y}.In(p.Rect)) { + return color.NYCbCrA{} + } + yi := p.YOffset(x, y) + ci := p.COffset(x, y) + ai := p.AOffset(x, y) + return color.NYCbCrA{ + color.YCbCr{ + Y: p.Y[yi], + Cb: p.Cb[ci], + Cr: p.Cr[ci], + }, + p.A[ai], + } +} + +// AOffset returns the index of the first element of A that corresponds to the +// pixel at (x, y). +func (p *NYCbCrA) AOffset(x, y int) int { + return (y-p.Rect.Min.Y)*p.AStride + (x - p.Rect.Min.X) +} + +// SubImage returns an image representing the portion of the image p visible +// through r. The returned value shares pixels with the original image. +func (p *NYCbCrA) SubImage(r Rectangle) Image { + r = r.Intersect(p.Rect) + // If r1 and r2 are Rectangles, r1.Intersect(r2) is not guaranteed to be inside + // either r1 or r2 if the intersection is empty. Without explicitly checking for + // this, the Pix[i:] expression below can panic. + if r.Empty() { + return &NYCbCrA{ + YCbCr: YCbCr{ + SubsampleRatio: p.SubsampleRatio, + }, + } + } + yi := p.YOffset(r.Min.X, r.Min.Y) + ci := p.COffset(r.Min.X, r.Min.Y) + ai := p.AOffset(r.Min.X, r.Min.Y) + return &NYCbCrA{ + YCbCr: YCbCr{ + Y: p.Y[yi:], + Cb: p.Cb[ci:], + Cr: p.Cr[ci:], + SubsampleRatio: p.SubsampleRatio, + YStride: p.YStride, + CStride: p.CStride, + Rect: r, + }, + A: p.A[ai:], + AStride: p.AStride, + } +} + +// Opaque scans the entire image and reports whether it is fully opaque. +func (p *NYCbCrA) Opaque() bool { + if p.Rect.Empty() { + return true + } + i0, i1 := 0, p.Rect.Dx() + for y := p.Rect.Min.Y; y < p.Rect.Max.Y; y++ { + for _, a := range p.A[i0:i1] { + if a != 0xff { + return false + } + } + i0 += p.AStride + i1 += p.AStride + } + return true +} + +// NewNYCbCrA returns a new NYCbCrA image with the given bounds and subsample +// ratio. +func NewNYCbCrA(r Rectangle, subsampleRatio YCbCrSubsampleRatio) *NYCbCrA { + w, h, cw, ch := yCbCrSize(r, subsampleRatio) + + // totalLength should be the same as i3, below, for a valid Rectangle r. + totalLength := add2NonNeg( + mul3NonNeg(2, w, h), + mul3NonNeg(2, cw, ch), + ) + if totalLength < 0 { + panic("image: NewNYCbCrA Rectangle has huge or negative dimension") + } + + i0 := 1*w*h + 0*cw*ch + i1 := 1*w*h + 1*cw*ch + i2 := 1*w*h + 2*cw*ch + i3 := 2*w*h + 2*cw*ch + b := make([]byte, i3) + return &NYCbCrA{ + YCbCr: YCbCr{ + Y: b[:i0:i0], + Cb: b[i0:i1:i1], + Cr: b[i1:i2:i2], + SubsampleRatio: subsampleRatio, + YStride: w, + CStride: cw, + Rect: r, + }, + A: b[i2:], + AStride: w, + } +} |