aw/go-resize
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Optimize YCbCr image resize

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This commit is contained in:
Charlie Vieth 2014-07-30 02:08:58 -04:00
parent 427b8d133e
commit eefd4737aa
6 changed files with 473 additions and 39 deletions
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93
converter.go
View File

@ -16,10 +16,7 @@ THIS SOFTWARE.
package resize
import (
"image"
"image/color"
)
import "image"
// Keep value in [0,255] range.
func clampUint8(in int32) uint8 {
@ -257,19 +254,81 @@ func resizeGray16(in *image.Gray16, out *image.Gray16, scale float64, coeffs []i
}
}
func convertYCbCrToRGBA(in *image.YCbCr) *image.RGBA {
out := image.NewRGBA(in.Bounds())
for y := 0; y < out.Bounds().Dy(); y++ {
for x := 0; x < out.Bounds().Dx(); x++ {
p := out.Pix[y*out.Stride+4*x:]
yi := in.YOffset(x, y)
ci := in.COffset(x, y)
r, g, b := color.YCbCrToRGB(in.Y[yi], in.Cb[ci], in.Cr[ci])
p[0] = r
p[1] = g
p[2] = b
p[3] = 0xff
func resizeYCbCr(in *ycc, out *ycc, scale float64, coeffs []int16, offset []int, filterLength int) {
oldBounds := in.Bounds()
newBounds := out.Bounds()
minX := oldBounds.Min.X * 3
maxX := (oldBounds.Max.X - oldBounds.Min.X - 1) * 3
for x := newBounds.Min.X; x < newBounds.Max.X; x++ {
row := in.Pix[(x-oldBounds.Min.Y)*in.Stride:]
for y := newBounds.Min.Y; y < newBounds.Max.Y; y++ {
var p [3]int32
var sum int32
start := offset[y]
ci := (y - newBounds.Min.Y) * filterLength
for i := 0; i < filterLength; i++ {
coeff := coeffs[ci+i]
if coeff != 0 {
xi := start + i
switch {
case uint(xi) < uint(oldBounds.Max.X):
xi *= 3
case xi >= oldBounds.Max.X:
xi = maxX
default:
xi = minX
}
p[0] += int32(coeff) * int32(row[xi+0])
p[1] += int32(coeff) * int32(row[xi+1])
p[2] += int32(coeff) * int32(row[xi+2])
sum += int32(coeff)
}
}
xo := (y-newBounds.Min.Y)*out.Stride + (x-newBounds.Min.X)*3
out.Pix[xo+0] = clampUint8(p[0] / sum)
out.Pix[xo+1] = clampUint8(p[1] / sum)
out.Pix[xo+2] = clampUint8(p[2] / sum)
}
}
}
func nearestYCbCr(in *ycc, out *ycc, scale float64, coeffs []bool, offset []int, filterLength int) {
oldBounds := in.Bounds()
newBounds := out.Bounds()
minX := oldBounds.Min.X * 3
maxX := (oldBounds.Max.X - oldBounds.Min.X - 1) * 3
for x := newBounds.Min.X; x < newBounds.Max.X; x++ {
row := in.Pix[(x-oldBounds.Min.Y)*in.Stride:]
for y := newBounds.Min.Y; y < newBounds.Max.Y; y++ {
var p [3]float32
var sum float32
start := offset[y]
ci := (y - newBounds.Min.Y) * filterLength
for i := 0; i < filterLength; i++ {
if coeffs[ci+i] {
xi := start + i
switch {
case uint(xi) < uint(oldBounds.Max.X):
xi *= 3
case xi >= oldBounds.Max.X:
xi = maxX
default:
xi = minX
}
p[0] += float32(row[xi+0])
p[1] += float32(row[xi+1])
p[2] += float32(row[xi+2])
sum++
}
}
xo := (y-newBounds.Min.Y)*out.Stride + (x-newBounds.Min.X)*3
out.Pix[xo+0] = floatToUint8(p[0] / sum)
out.Pix[xo+1] = floatToUint8(p[1] / sum)
out.Pix[xo+2] = floatToUint8(p[2] / sum)
}
}
return out
}

16
nearest.go
View File

@ -1,3 +1,19 @@
/*
Copyright (c) 2014, Charlie Vieth <charlie.vieth@gmail.com>
Permission to use, copy, modify, and/or distribute this software for any purpose
with or without fee is hereby granted, provided that the above copyright notice
and this permission notice appear in all copies.
THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS
OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF
THIS SOFTWARE.
*/
package resize
import "image"

16
nearest_test.go
View File

@ -1,3 +1,19 @@
/*
Copyright (c) 2014, Charlie Vieth <charlie.vieth@gmail.com>
Permission to use, copy, modify, and/or distribute this software for any purpose
with or without fee is hereby granted, provided that the above copyright notice
and this permission notice appear in all copies.
THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS
OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF
THIS SOFTWARE.
*/
package resize
import "testing"

40
resize.go
View File

@ -129,35 +129,33 @@ func Resize(width, height uint, img image.Image, interp InterpolationFunction) i
case *image.YCbCr:
// 8-bit precision
// accessing the YCbCr arrays in a tight loop is slow.
// converting the image before filtering will improve performance.
inputAsRGBA := convertYCbCrToRGBA(input)
temp := image.NewRGBA(image.Rect(0, 0, input.Bounds().Dy(), int(width)))
result := image.NewRGBA(image.Rect(0, 0, int(width), int(height)))
// converting the image to ycc increases performance by 2x.
temp := newYCC(image.Rect(0, 0, input.Bounds().Dy(), int(width)), input.SubsampleRatio)
result := newYCC(image.Rect(0, 0, int(width), int(height)), input.SubsampleRatio)
// horizontal filter, results in transposed temporary image
coeffs, offset, filterLength := createWeights8(temp.Bounds().Dy(), input.Bounds().Min.X, taps, blur, scaleX, kernel)
in := imageYCbCrToYCC(input)
wg.Add(cpus)
for i := 0; i < cpus; i++ {
slice := makeSlice(temp, i, cpus).(*image.RGBA)
slice := makeSlice(temp, i, cpus).(*ycc)
go func() {
defer wg.Done()
resizeRGBA(inputAsRGBA, slice, scaleX, coeffs, offset, filterLength)
resizeYCbCr(in, slice, scaleX, coeffs, offset, filterLength)
}()
}
wg.Wait()
// horizontal filter on transposed image, result is not transposed
coeffs, offset, filterLength = createWeights8(result.Bounds().Dy(), temp.Bounds().Min.X, taps, blur, scaleY, kernel)
wg.Add(cpus)
for i := 0; i < cpus; i++ {
slice := makeSlice(result, i, cpus).(*image.RGBA)
slice := makeSlice(result, i, cpus).(*ycc)
go func() {
defer wg.Done()
resizeRGBA(temp, slice, scaleY, coeffs, offset, filterLength)
resizeYCbCr(temp, slice, scaleY, coeffs, offset, filterLength)
}()
}
wg.Wait()
return result
return result.YCbCr()
case *image.RGBA64:
// 16-bit precision
temp := image.NewRGBA64(image.Rect(0, 0, input.Bounds().Dy(), int(width)))
@ -315,35 +313,33 @@ func resizeNearest(width, height uint, scaleX, scaleY float64, img image.Image,
case *image.YCbCr:
// 8-bit precision
// accessing the YCbCr arrays in a tight loop is slow.
// converting the image before filtering will improve performance.
inputAsRGBA := convertYCbCrToRGBA(input)
temp := image.NewRGBA(image.Rect(0, 0, input.Bounds().Dy(), int(width)))
result := image.NewRGBA(image.Rect(0, 0, int(width), int(height)))
// converting the image to ycc increases performance by 2x.
temp := newYCC(image.Rect(0, 0, input.Bounds().Dy(), int(width)), input.SubsampleRatio)
result := newYCC(image.Rect(0, 0, int(width), int(height)), input.SubsampleRatio)
// horizontal filter, results in transposed temporary image
coeffs, offset, filterLength := createWeightsNearest(temp.Bounds().Dy(), input.Bounds().Min.X, taps, blur, scaleX)
in := imageYCbCrToYCC(input)
wg.Add(cpus)
for i := 0; i < cpus; i++ {
slice := makeSlice(temp, i, cpus).(*image.RGBA)
slice := makeSlice(temp, i, cpus).(*ycc)
go func() {
defer wg.Done()
nearestRGBA(inputAsRGBA, slice, scaleX, coeffs, offset, filterLength)
nearestYCbCr(in, slice, scaleX, coeffs, offset, filterLength)
}()
}
wg.Wait()
// horizontal filter on transposed image, result is not transposed
coeffs, offset, filterLength = createWeightsNearest(result.Bounds().Dy(), temp.Bounds().Min.X, taps, blur, scaleY)
wg.Add(cpus)
for i := 0; i < cpus; i++ {
slice := makeSlice(result, i, cpus).(*image.RGBA)
slice := makeSlice(result, i, cpus).(*ycc)
go func() {
defer wg.Done()
nearestRGBA(temp, slice, scaleY, coeffs, offset, filterLength)
nearestYCbCr(temp, slice, scaleY, coeffs, offset, filterLength)
}()
}
wg.Wait()
return result
return result.YCbCr()
case *image.RGBA64:
// 16-bit precision
temp := image.NewRGBA64(image.Rect(0, 0, input.Bounds().Dy(), int(width)))

226
ycc.go Normal file
View File

@ -0,0 +1,226 @@
/*
Copyright (c) 2014, Charlie Vieth <charlie.vieth@gmail.com>
Permission to use, copy, modify, and/or distribute this software for any purpose
with or without fee is hereby granted, provided that the above copyright notice
and this permission notice appear in all copies.
THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS
OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF
THIS SOFTWARE.
*/
package resize
import (
"image"
"image/color"
)
// ycc is an in memory YCbCr image. The Y, Cb and Cr samples are held in a
// single slice to increase resizing performance.
type ycc struct {
// Pix holds the image's pixels, in Y, Cb, Cr order. The pixel at
// (x, y) starts at Pix[(y-Rect.Min.Y)*Stride + (x-Rect.Min.X)*3].
Pix []uint8
// Stride is the Pix stride (in bytes) between vertically adjacent pixels.
Stride int
// Rect is the image's bounds.
Rect image.Rectangle
// SubsampleRatio is the subsample ratio of the original YCbCr image.
SubsampleRatio image.YCbCrSubsampleRatio
}
// PixOffset returns the index of the first element of Pix that corresponds to
// the pixel at (x, y).
func (p *ycc) PixOffset(x, y int) int {
return (y * p.Stride) + (x * 3)
}
func (p *ycc) Bounds() image.Rectangle {
return p.Rect
}
func (p *ycc) ColorModel() color.Model {
return color.YCbCrModel
}
func (p *ycc) At(x, y int) color.Color {
if !(image.Point{x, y}.In(p.Rect)) {
return color.YCbCr{}
}
i := p.PixOffset(x, y)
return color.YCbCr{
p.Pix[i+0],
p.Pix[i+1],
p.Pix[i+2],
}
}
func (p *ycc) Opaque() bool {
return true
}
// 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 *ycc) SubImage(r image.Rectangle) image.Image {
r = r.Intersect(p.Rect)
if r.Empty() {
return &ycc{SubsampleRatio: p.SubsampleRatio}
}
i := p.PixOffset(r.Min.X, r.Min.Y)
return &ycc{
Pix: p.Pix[i:],
Stride: p.Stride,
Rect: r,
SubsampleRatio: p.SubsampleRatio,
}
}
// newYCC returns a new ycc with the given bounds and subsample ratio.
func newYCC(r image.Rectangle, s image.YCbCrSubsampleRatio) *ycc {
w, h := r.Dx(), r.Dy()
buf := make([]uint8, 3*w*h)
return &ycc{Pix: buf, Stride: 3 * w, Rect: r, SubsampleRatio: s}
}
// YCbCr converts ycc to a YCbCr image with the same subsample ratio
// as the YCbCr image that ycc was generated from.
func (p *ycc) YCbCr() *image.YCbCr {
ycbcr := image.NewYCbCr(p.Rect, p.SubsampleRatio)
var off int
switch ycbcr.SubsampleRatio {
case image.YCbCrSubsampleRatio422:
for y := ycbcr.Rect.Min.Y; y < ycbcr.Rect.Max.Y; y++ {
yy := (y - ycbcr.Rect.Min.Y) * ycbcr.YStride
cy := (y - ycbcr.Rect.Min.Y) * ycbcr.CStride
for x := ycbcr.Rect.Min.X; x < ycbcr.Rect.Max.X; x++ {
xx := (x - ycbcr.Rect.Min.X)
yi := yy + xx
ci := cy + xx/2
ycbcr.Y[yi] = p.Pix[off+0]
ycbcr.Cb[ci] = p.Pix[off+1]
ycbcr.Cr[ci] = p.Pix[off+2]
off += 3
}
}
case image.YCbCrSubsampleRatio420:
for y := ycbcr.Rect.Min.Y; y < ycbcr.Rect.Max.Y; y++ {
yy := (y - ycbcr.Rect.Min.Y) * ycbcr.YStride
cy := (y/2 - ycbcr.Rect.Min.Y/2) * ycbcr.CStride
for x := ycbcr.Rect.Min.X; x < ycbcr.Rect.Max.X; x++ {
xx := (x - ycbcr.Rect.Min.X)
yi := yy + xx
ci := cy + xx/2
ycbcr.Y[yi] = p.Pix[off+0]
ycbcr.Cb[ci] = p.Pix[off+1]
ycbcr.Cr[ci] = p.Pix[off+2]
off += 3
}
}
case image.YCbCrSubsampleRatio440:
for y := ycbcr.Rect.Min.Y; y < ycbcr.Rect.Max.Y; y++ {
yy := (y - ycbcr.Rect.Min.Y) * ycbcr.YStride
cy := (y/2 - ycbcr.Rect.Min.Y/2) * ycbcr.CStride
for x := ycbcr.Rect.Min.X; x < ycbcr.Rect.Max.X; x++ {
xx := (x - ycbcr.Rect.Min.X)
yi := yy + xx
ci := cy + xx
ycbcr.Y[yi] = p.Pix[off+0]
ycbcr.Cb[ci] = p.Pix[off+1]
ycbcr.Cr[ci] = p.Pix[off+2]
off += 3
}
}
default:
// Default to 4:4:4 subsampling.
for y := ycbcr.Rect.Min.Y; y < ycbcr.Rect.Max.Y; y++ {
yy := (y - ycbcr.Rect.Min.Y) * ycbcr.YStride
cy := (y - ycbcr.Rect.Min.Y) * ycbcr.CStride
for x := ycbcr.Rect.Min.X; x < ycbcr.Rect.Max.X; x++ {
xx := (x - ycbcr.Rect.Min.X)
yi := yy + xx
ci := cy + xx
ycbcr.Y[yi] = p.Pix[off+0]
ycbcr.Cb[ci] = p.Pix[off+1]
ycbcr.Cr[ci] = p.Pix[off+2]
off += 3
}
}
}
return ycbcr
}
// imageYCbCrToYCC converts a YCbCr image to a ycc image for resizing.
func imageYCbCrToYCC(in *image.YCbCr) *ycc {
w, h := in.Rect.Dx(), in.Rect.Dy()
buf := make([]uint8, 3*w*h)
p := ycc{Pix: buf, Stride: 3 * w, Rect: in.Rect, SubsampleRatio: in.SubsampleRatio}
var off int
switch in.SubsampleRatio {
case image.YCbCrSubsampleRatio422:
for y := in.Rect.Min.Y; y < in.Rect.Max.Y; y++ {
yy := (y - in.Rect.Min.Y) * in.YStride
cy := (y - in.Rect.Min.Y) * in.CStride
for x := in.Rect.Min.X; x < in.Rect.Max.X; x++ {
xx := (x - in.Rect.Min.X)
yi := yy + xx
ci := cy + xx/2
p.Pix[off+0] = in.Y[yi]
p.Pix[off+1] = in.Cb[ci]
p.Pix[off+2] = in.Cr[ci]
off += 3
}
}
case image.YCbCrSubsampleRatio420:
for y := in.Rect.Min.Y; y < in.Rect.Max.Y; y++ {
yy := (y - in.Rect.Min.Y) * in.YStride
cy := (y/2 - in.Rect.Min.Y/2) * in.CStride
for x := in.Rect.Min.X; x < in.Rect.Max.X; x++ {
xx := (x - in.Rect.Min.X)
yi := yy + xx
ci := cy + xx/2
p.Pix[off+0] = in.Y[yi]
p.Pix[off+1] = in.Cb[ci]
p.Pix[off+2] = in.Cr[ci]
off += 3
}
}
case image.YCbCrSubsampleRatio440:
for y := in.Rect.Min.Y; y < in.Rect.Max.Y; y++ {
yy := (y - in.Rect.Min.Y) * in.YStride
cy := (y/2 - in.Rect.Min.Y/2) * in.CStride
for x := in.Rect.Min.X; x < in.Rect.Max.X; x++ {
xx := (x - in.Rect.Min.X)
yi := yy + xx
ci := cy + xx
p.Pix[off+0] = in.Y[yi]
p.Pix[off+1] = in.Cb[ci]
p.Pix[off+2] = in.Cr[ci]
off += 3
}
}
default:
// Default to 4:4:4 subsampling.
for y := in.Rect.Min.Y; y < in.Rect.Max.Y; y++ {
yy := (y - in.Rect.Min.Y) * in.YStride
cy := (y - in.Rect.Min.Y) * in.CStride
for x := in.Rect.Min.X; x < in.Rect.Max.X; x++ {
xx := (x - in.Rect.Min.X)
yi := yy + xx
ci := cy + xx
p.Pix[off+0] = in.Y[yi]
p.Pix[off+1] = in.Cb[ci]
p.Pix[off+2] = in.Cr[ci]
off += 3
}
}
}
return &p
}

121
ycc_test.go Normal file
View File

@ -0,0 +1,121 @@
/*
Copyright (c) 2014, Charlie Vieth <charlie.vieth@gmail.com>
Permission to use, copy, modify, and/or distribute this software for any purpose
with or without fee is hereby granted, provided that the above copyright notice
and this permission notice appear in all copies.
THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS
OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF
THIS SOFTWARE.
*/
package resize
import (
"image"
"testing"
)
type Image interface {
image.Image
SubImage(image.Rectangle) image.Image
}
func TestImage(t *testing.T) {
testImage := []Image{
newYCC(image.Rect(0, 0, 10, 10), image.YCbCrSubsampleRatio420),
newYCC(image.Rect(0, 0, 10, 10), image.YCbCrSubsampleRatio422),
newYCC(image.Rect(0, 0, 10, 10), image.YCbCrSubsampleRatio440),
newYCC(image.Rect(0, 0, 10, 10), image.YCbCrSubsampleRatio444),
}
for _, m := range testImage {
if !image.Rect(0, 0, 10, 10).Eq(m.Bounds()) {
t.Errorf("%T: want bounds %v, got %v",
m, image.Rect(0, 0, 10, 10), m.Bounds())
continue
}
m = m.SubImage(image.Rect(3, 2, 9, 8)).(Image)
if !image.Rect(3, 2, 9, 8).Eq(m.Bounds()) {
t.Errorf("%T: sub-image want bounds %v, got %v",
m, image.Rect(3, 2, 9, 8), m.Bounds())
continue
}
// Test that taking an empty sub-image starting at a corner does not panic.
m.SubImage(image.Rect(0, 0, 0, 0))
m.SubImage(image.Rect(10, 0, 10, 0))
m.SubImage(image.Rect(0, 10, 0, 10))
m.SubImage(image.Rect(10, 10, 10, 10))
}
}
func TestConvertYCbCr(t *testing.T) {
testImage := []Image{
image.NewYCbCr(image.Rect(0, 0, 50, 50), image.YCbCrSubsampleRatio420),
image.NewYCbCr(image.Rect(0, 0, 50, 50), image.YCbCrSubsampleRatio422),
image.NewYCbCr(image.Rect(0, 0, 50, 50), image.YCbCrSubsampleRatio440),
image.NewYCbCr(image.Rect(0, 0, 50, 50), image.YCbCrSubsampleRatio444),
}
for _, img := range testImage {
m := img.(*image.YCbCr)
for y := m.Rect.Min.Y; y < m.Rect.Max.Y; y++ {
for x := m.Rect.Min.X; x < m.Rect.Max.X; x++ {
yi := m.YOffset(x, y)
ci := m.COffset(x, y)
m.Y[yi] = uint8(16*y + x)
m.Cb[ci] = uint8(y + 16*x)
m.Cr[ci] = uint8(y + 16*x)
}
}
// test conversion from YCbCr to ycc
yc := imageYCbCrToYCC(m)
for y := m.Rect.Min.Y; y < m.Rect.Max.Y; y++ {
for x := m.Rect.Min.X; x < m.Rect.Max.X; x++ {
ystride := 3 * (m.Rect.Max.X - m.Rect.Min.X)
xstride := 3
yi := m.YOffset(x, y)
ci := m.COffset(x, y)
si := (y * ystride) + (x * xstride)
if m.Y[yi] != yc.Pix[si] {
t.Errorf("Err Y - found: %d expected: %d x: %d y: %d yi: %d si: %d",
m.Y[yi], yc.Pix[si], x, y, yi, si)
}
if m.Cb[ci] != yc.Pix[si+1] {
t.Errorf("Err Cb - found: %d expected: %d x: %d y: %d ci: %d si: %d",
m.Cb[ci], yc.Pix[si+1], x, y, ci, si+1)
}
if m.Cr[ci] != yc.Pix[si+2] {
t.Errorf("Err Cr - found: %d expected: %d x: %d y: %d ci: %d si: %d",
m.Cr[ci], yc.Pix[si+2], x, y, ci, si+2)
}
}
}
// test conversion from ycc back to YCbCr
ym := yc.YCbCr()
for y := m.Rect.Min.Y; y < m.Rect.Max.Y; y++ {
for x := m.Rect.Min.X; x < m.Rect.Max.X; x++ {
yi := m.YOffset(x, y)
ci := m.COffset(x, y)
if m.Y[yi] != ym.Y[yi] {
t.Errorf("Err Y - found: %d expected: %d x: %d y: %d yi: %d",
m.Y[yi], ym.Y[yi], x, y, yi)
}
if m.Cb[ci] != ym.Cb[ci] {
t.Errorf("Err Cb - found: %d expected: %d x: %d y: %d ci: %d",
m.Cb[ci], ym.Cb[ci], x, y, ci)
}
if m.Cr[ci] != ym.Cr[ci] {
t.Errorf("Err Cr - found: %d expected: %d x: %d y: %d ci: %d",
m.Cr[ci], ym.Cr[ci], x, y, ci)
}
}
}
}
}