228 lines
6.5 KiB
Go
228 lines
6.5 KiB
Go
/*
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Copyright (c) 2014, Charlie Vieth <charlie.vieth@gmail.com>
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Permission to use, copy, modify, and/or distribute this software for any purpose
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with or without fee is hereby granted, provided that the above copyright notice
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and this permission notice appear in all copies.
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THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
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REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
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FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
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INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS
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OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
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TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF
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THIS SOFTWARE.
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*/
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package resize
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import (
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"image"
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"image/color"
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)
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// ycc is an in memory YCbCr image. The Y, Cb and Cr samples are held in a
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// single slice to increase resizing performance.
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type ycc struct {
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// Pix holds the image's pixels, in Y, Cb, Cr order. The pixel at
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// (x, y) starts at Pix[(y-Rect.Min.Y)*Stride + (x-Rect.Min.X)*3].
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Pix []uint8
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// Stride is the Pix stride (in bytes) between vertically adjacent pixels.
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Stride int
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// Rect is the image's bounds.
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Rect image.Rectangle
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// SubsampleRatio is the subsample ratio of the original YCbCr image.
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SubsampleRatio image.YCbCrSubsampleRatio
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}
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// PixOffset returns the index of the first element of Pix that corresponds to
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// the pixel at (x, y).
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func (p *ycc) PixOffset(x, y int) int {
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return (y-p.Rect.Min.Y)*p.Stride + (x-p.Rect.Min.X)*3
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}
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func (p *ycc) Bounds() image.Rectangle {
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return p.Rect
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}
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func (p *ycc) ColorModel() color.Model {
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return color.YCbCrModel
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}
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func (p *ycc) At(x, y int) color.Color {
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if !(image.Point{x, y}.In(p.Rect)) {
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return color.YCbCr{}
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}
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i := p.PixOffset(x, y)
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return color.YCbCr{
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p.Pix[i+0],
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p.Pix[i+1],
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p.Pix[i+2],
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}
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}
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func (p *ycc) Opaque() bool {
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return true
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}
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// SubImage returns an image representing the portion of the image p visible
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// through r. The returned value shares pixels with the original image.
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func (p *ycc) SubImage(r image.Rectangle) image.Image {
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r = r.Intersect(p.Rect)
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if r.Empty() {
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return &ycc{SubsampleRatio: p.SubsampleRatio}
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}
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i := p.PixOffset(r.Min.X, r.Min.Y)
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return &ycc{
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Pix: p.Pix[i:],
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Stride: p.Stride,
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Rect: r,
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SubsampleRatio: p.SubsampleRatio,
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}
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}
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// newYCC returns a new ycc with the given bounds and subsample ratio.
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func newYCC(r image.Rectangle, s image.YCbCrSubsampleRatio) *ycc {
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w, h := r.Dx(), r.Dy()
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buf := make([]uint8, 3*w*h)
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return &ycc{Pix: buf, Stride: 3 * w, Rect: r, SubsampleRatio: s}
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}
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// YCbCr converts ycc to a YCbCr image with the same subsample ratio
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// as the YCbCr image that ycc was generated from.
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func (p *ycc) YCbCr() *image.YCbCr {
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ycbcr := image.NewYCbCr(p.Rect, p.SubsampleRatio)
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var off int
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switch ycbcr.SubsampleRatio {
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case image.YCbCrSubsampleRatio422:
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for y := ycbcr.Rect.Min.Y; y < ycbcr.Rect.Max.Y; y++ {
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yy := (y - ycbcr.Rect.Min.Y) * ycbcr.YStride
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cy := (y - ycbcr.Rect.Min.Y) * ycbcr.CStride
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for x := ycbcr.Rect.Min.X; x < ycbcr.Rect.Max.X; x++ {
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xx := (x - ycbcr.Rect.Min.X)
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yi := yy + xx
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ci := cy + xx/2
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ycbcr.Y[yi] = p.Pix[off+0]
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ycbcr.Cb[ci] = p.Pix[off+1]
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ycbcr.Cr[ci] = p.Pix[off+2]
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off += 3
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}
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}
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case image.YCbCrSubsampleRatio420:
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for y := ycbcr.Rect.Min.Y; y < ycbcr.Rect.Max.Y; y++ {
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yy := (y - ycbcr.Rect.Min.Y) * ycbcr.YStride
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cy := (y/2 - ycbcr.Rect.Min.Y/2) * ycbcr.CStride
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for x := ycbcr.Rect.Min.X; x < ycbcr.Rect.Max.X; x++ {
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xx := (x - ycbcr.Rect.Min.X)
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yi := yy + xx
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ci := cy + xx/2
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ycbcr.Y[yi] = p.Pix[off+0]
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ycbcr.Cb[ci] = p.Pix[off+1]
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ycbcr.Cr[ci] = p.Pix[off+2]
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off += 3
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}
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}
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case image.YCbCrSubsampleRatio440:
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for y := ycbcr.Rect.Min.Y; y < ycbcr.Rect.Max.Y; y++ {
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yy := (y - ycbcr.Rect.Min.Y) * ycbcr.YStride
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cy := (y/2 - ycbcr.Rect.Min.Y/2) * ycbcr.CStride
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for x := ycbcr.Rect.Min.X; x < ycbcr.Rect.Max.X; x++ {
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xx := (x - ycbcr.Rect.Min.X)
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yi := yy + xx
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ci := cy + xx
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ycbcr.Y[yi] = p.Pix[off+0]
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ycbcr.Cb[ci] = p.Pix[off+1]
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ycbcr.Cr[ci] = p.Pix[off+2]
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off += 3
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}
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}
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default:
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// Default to 4:4:4 subsampling.
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for y := ycbcr.Rect.Min.Y; y < ycbcr.Rect.Max.Y; y++ {
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yy := (y - ycbcr.Rect.Min.Y) * ycbcr.YStride
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cy := (y - ycbcr.Rect.Min.Y) * ycbcr.CStride
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for x := ycbcr.Rect.Min.X; x < ycbcr.Rect.Max.X; x++ {
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xx := (x - ycbcr.Rect.Min.X)
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yi := yy + xx
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ci := cy + xx
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ycbcr.Y[yi] = p.Pix[off+0]
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ycbcr.Cb[ci] = p.Pix[off+1]
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ycbcr.Cr[ci] = p.Pix[off+2]
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off += 3
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}
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}
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}
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return ycbcr
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}
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// imageYCbCrToYCC converts a YCbCr image to a ycc image for resizing.
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func imageYCbCrToYCC(in *image.YCbCr) *ycc {
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w, h := in.Rect.Dx(), in.Rect.Dy()
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r := image.Rect(0, 0, w, h)
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buf := make([]uint8, 3*w*h)
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p := ycc{Pix: buf, Stride: 3 * w, Rect: r, SubsampleRatio: in.SubsampleRatio}
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var off int
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switch in.SubsampleRatio {
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case image.YCbCrSubsampleRatio422:
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for y := in.Rect.Min.Y; y < in.Rect.Max.Y; y++ {
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yy := (y - in.Rect.Min.Y) * in.YStride
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cy := (y - in.Rect.Min.Y) * in.CStride
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for x := in.Rect.Min.X; x < in.Rect.Max.X; x++ {
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xx := (x - in.Rect.Min.X)
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yi := yy + xx
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ci := cy + xx/2
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p.Pix[off+0] = in.Y[yi]
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p.Pix[off+1] = in.Cb[ci]
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p.Pix[off+2] = in.Cr[ci]
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off += 3
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}
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}
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case image.YCbCrSubsampleRatio420:
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for y := in.Rect.Min.Y; y < in.Rect.Max.Y; y++ {
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yy := (y - in.Rect.Min.Y) * in.YStride
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cy := (y/2 - in.Rect.Min.Y/2) * in.CStride
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for x := in.Rect.Min.X; x < in.Rect.Max.X; x++ {
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xx := (x - in.Rect.Min.X)
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yi := yy + xx
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ci := cy + xx/2
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p.Pix[off+0] = in.Y[yi]
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p.Pix[off+1] = in.Cb[ci]
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p.Pix[off+2] = in.Cr[ci]
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off += 3
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}
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}
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case image.YCbCrSubsampleRatio440:
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for y := in.Rect.Min.Y; y < in.Rect.Max.Y; y++ {
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yy := (y - in.Rect.Min.Y) * in.YStride
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cy := (y/2 - in.Rect.Min.Y/2) * in.CStride
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for x := in.Rect.Min.X; x < in.Rect.Max.X; x++ {
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xx := (x - in.Rect.Min.X)
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yi := yy + xx
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ci := cy + xx
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p.Pix[off+0] = in.Y[yi]
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p.Pix[off+1] = in.Cb[ci]
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p.Pix[off+2] = in.Cr[ci]
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off += 3
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}
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}
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default:
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// Default to 4:4:4 subsampling.
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for y := in.Rect.Min.Y; y < in.Rect.Max.Y; y++ {
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yy := (y - in.Rect.Min.Y) * in.YStride
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cy := (y - in.Rect.Min.Y) * in.CStride
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for x := in.Rect.Min.X; x < in.Rect.Max.X; x++ {
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xx := (x - in.Rect.Min.X)
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yi := yy + xx
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ci := cy + xx
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p.Pix[off+0] = in.Y[yi]
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p.Pix[off+1] = in.Cb[ci]
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p.Pix[off+2] = in.Cr[ci]
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off += 3
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}
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}
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}
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return &p
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}
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