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// // 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}.inside(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}.inside(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,
// }
// }