aw/go-resize
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Use RGBA, RGBA64 image types as output.

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These image types use premultiplied alpha values which are also used during the interpolation. If we'd use NRGBA, NRGBA64 as output, we'd have to reverse the premultiplication.
This commit is contained in:
nfnt 2016-01-07 21:25:38 +01:00
parent 9780a95734
commit 0f9f918da3
3 changed files with 59 additions and 111 deletions
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104
converter.go
View File

@ -43,7 +43,7 @@ func clampUint16(in int64) uint16 {
return 0
}
func resizeGeneric(in image.Image, out *image.NRGBA64, scale float64, coeffs []int32, offset []int, filterLength int) {
func resizeGeneric(in image.Image, out *image.RGBA64, scale float64, coeffs []int32, offset []int, filterLength int) {
newBounds := out.Bounds()
maxX := in.Bounds().Dx() - 1
@ -63,7 +63,7 @@ func resizeGeneric(in image.Image, out *image.NRGBA64, scale float64, coeffs []i
case xi >= maxX:
xi = maxX
}
// Forward alpha-premultiplication (if needed)
r, g, b, a := in.At(xi+in.Bounds().Min.X, x+in.Bounds().Min.Y).RGBA()
rgba[0] += int64(coeff) * int64(r)
@ -75,34 +75,24 @@ func resizeGeneric(in image.Image, out *image.NRGBA64, scale float64, coeffs []i
}
offset := (y-newBounds.Min.Y)*out.Stride + (x-newBounds.Min.X)*8
// Reverse alpha-premultiplication
r := rgba[0] / sum
g := rgba[1] / sum
b := rgba[2] / sum
a := rgba[3] / sum
if a != 0 {
r = r * 0xffff / a
g = g * 0xffff / a
b = b * 0xffff / a
}
value := clampUint16(r)
value := clampUint16(rgba[0] / sum)
out.Pix[offset+0] = uint8(value >> 8)
out.Pix[offset+1] = uint8(value)
value = clampUint16(g)
value = clampUint16(rgba[1] / sum)
out.Pix[offset+2] = uint8(value >> 8)
out.Pix[offset+3] = uint8(value)
value = clampUint16(b)
value = clampUint16(rgba[2] / sum)
out.Pix[offset+4] = uint8(value >> 8)
out.Pix[offset+5] = uint8(value)
value = clampUint16(a)
value = clampUint16(rgba[3] / sum)
out.Pix[offset+6] = uint8(value >> 8)
out.Pix[offset+7] = uint8(value)
}
}
}
func resizeRGBA(in *image.RGBA, out *image.NRGBA, scale float64, coeffs []int16, offset []int, filterLength int) {
func resizeRGBA(in *image.RGBA, out *image.RGBA, scale float64, coeffs []int16, offset []int, filterLength int) {
newBounds := out.Bounds()
maxX := in.Bounds().Dx() - 1
@ -135,27 +125,16 @@ func resizeRGBA(in *image.RGBA, out *image.NRGBA, scale float64, coeffs []int16,
}
xo := (y-newBounds.Min.Y)*out.Stride + (x-newBounds.Min.X)*4
// Reverse alpha-premultiplication
r := rgba[0] / sum
g := rgba[1] / sum
b := rgba[2] / sum
a := rgba[3] / sum
if a != 0 {
r = r * 0xff / a
g = g * 0xff / a
b = b * 0xff / a
}
out.Pix[xo+0] = clampUint8(r)
out.Pix[xo+1] = clampUint8(g)
out.Pix[xo+2] = clampUint8(b)
out.Pix[xo+3] = clampUint8(a)
out.Pix[xo+0] = clampUint8(rgba[0] / sum)
out.Pix[xo+1] = clampUint8(rgba[1] / sum)
out.Pix[xo+2] = clampUint8(rgba[2] / sum)
out.Pix[xo+3] = clampUint8(rgba[3] / sum)
}
}
}
func resizeNRGBA(in *image.NRGBA, out *image.NRGBA, scale float64, coeffs []int16, offset []int, filterLength int) {
func resizeNRGBA(in *image.NRGBA, out *image.RGBA, scale float64, coeffs []int16, offset []int, filterLength int) {
newBounds := out.Bounds()
maxX := in.Bounds().Dx() - 1
@ -190,27 +169,16 @@ func resizeNRGBA(in *image.NRGBA, out *image.NRGBA, scale float64, coeffs []int1
}
xo := (y-newBounds.Min.Y)*out.Stride + (x-newBounds.Min.X)*4
// Reverse alpha-premultiplication
r := rgba[0] / sum
g := rgba[1] / sum
b := rgba[2] / sum
a := rgba[3] / sum
if a != 0 {
r = r * 0xff / a
g = g * 0xff / a
b = b * 0xff / a
}
out.Pix[xo+0] = clampUint8(r)
out.Pix[xo+1] = clampUint8(g)
out.Pix[xo+2] = clampUint8(b)
out.Pix[xo+3] = clampUint8(a)
out.Pix[xo+0] = clampUint8(rgba[0] / sum)
out.Pix[xo+1] = clampUint8(rgba[1] / sum)
out.Pix[xo+2] = clampUint8(rgba[2] / sum)
out.Pix[xo+3] = clampUint8(rgba[3] / sum)
}
}
}
func resizeRGBA64(in *image.RGBA64, out *image.NRGBA64, scale float64, coeffs []int32, offset []int, filterLength int) {
func resizeRGBA64(in *image.RGBA64, out *image.RGBA64, scale float64, coeffs []int32, offset []int, filterLength int) {
newBounds := out.Bounds()
maxX := in.Bounds().Dx() - 1
@ -243,34 +211,24 @@ func resizeRGBA64(in *image.RGBA64, out *image.NRGBA64, scale float64, coeffs []
}
xo := (y-newBounds.Min.Y)*out.Stride + (x-newBounds.Min.X)*8
// Reverse alpha-premultiplication
r := rgba[0] / sum
g := rgba[1] / sum
b := rgba[2] / sum
a := rgba[3] / sum
if a != 0 {
r = r * 0xffff / a
g = g * 0xffff / a
b = b * 0xffff / a
}
value := clampUint16(r)
value := clampUint16(rgba[0] / sum)
out.Pix[xo+0] = uint8(value >> 8)
out.Pix[xo+1] = uint8(value)
value = clampUint16(g)
value = clampUint16(rgba[1] / sum)
out.Pix[xo+2] = uint8(value >> 8)
out.Pix[xo+3] = uint8(value)
value = clampUint16(b)
value = clampUint16(rgba[2] / sum)
out.Pix[xo+4] = uint8(value >> 8)
out.Pix[xo+5] = uint8(value)
value = clampUint16(a)
value = clampUint16(rgba[3] / sum)
out.Pix[xo+6] = uint8(value >> 8)
out.Pix[xo+7] = uint8(value)
}
}
}
func resizeNRGBA64(in *image.NRGBA64, out *image.NRGBA64, scale float64, coeffs []int32, offset []int, filterLength int) {
func resizeNRGBA64(in *image.NRGBA64, out *image.RGBA64, scale float64, coeffs []int32, offset []int, filterLength int) {
newBounds := out.Bounds()
maxX := in.Bounds().Dx() - 1
@ -305,27 +263,17 @@ func resizeNRGBA64(in *image.NRGBA64, out *image.NRGBA64, scale float64, coeffs
}
xo := (y-newBounds.Min.Y)*out.Stride + (x-newBounds.Min.X)*8
// Reverse alpha-premultiplication
r := rgba[0] / sum
g := rgba[1] / sum
b := rgba[2] / sum
a := rgba[3] / sum
if a != 0 {
r = r * 0xffff / a
g = g * 0xffff / a
b = b * 0xffff / a
}
value := clampUint16(r)
value := clampUint16(rgba[0] / sum)
out.Pix[xo+0] = uint8(value >> 8)
out.Pix[xo+1] = uint8(value)
value = clampUint16(g)
value = clampUint16(rgba[1] / sum)
out.Pix[xo+2] = uint8(value >> 8)
out.Pix[xo+3] = uint8(value)
value = clampUint16(b)
value = clampUint16(rgba[2] / sum)
out.Pix[xo+4] = uint8(value >> 8)
out.Pix[xo+5] = uint8(value)
value = clampUint16(a)
value = clampUint16(rgba[3] / sum)
out.Pix[xo+6] = uint8(value >> 8)
out.Pix[xo+7] = uint8(value)
}

50
resize.go
View File

@ -105,14 +105,14 @@ func Resize(width, height uint, img image.Image, interp InterpolationFunction) i
switch input := img.(type) {
case *image.RGBA:
// 8-bit precision
temp := image.NewNRGBA(image.Rect(0, 0, input.Bounds().Dy(), int(width)))
result := image.NewNRGBA(image.Rect(0, 0, int(width), int(height)))
temp := image.NewRGBA(image.Rect(0, 0, input.Bounds().Dy(), int(width)))
result := image.NewRGBA(image.Rect(0, 0, int(width), int(height)))
// horizontal filter, results in transposed temporary image
coeffs, offset, filterLength := createWeights8(temp.Bounds().Dy(), taps, blur, scaleX, kernel)
wg.Add(cpus)
for i := 0; i < cpus; i++ {
slice := makeSlice(temp, i, cpus).(*image.NRGBA)
slice := makeSlice(temp, i, cpus).(*image.RGBA)
go func() {
defer wg.Done()
resizeRGBA(input, slice, scaleX, coeffs, offset, filterLength)
@ -124,24 +124,24 @@ func Resize(width, height uint, img image.Image, interp InterpolationFunction) i
coeffs, offset, filterLength = createWeights8(result.Bounds().Dy(), taps, blur, scaleY, kernel)
wg.Add(cpus)
for i := 0; i < cpus; i++ {
slice := makeSlice(result, i, cpus).(*image.NRGBA)
slice := makeSlice(result, i, cpus).(*image.RGBA)
go func() {
defer wg.Done()
resizeNRGBA(temp, slice, scaleY, coeffs, offset, filterLength)
resizeRGBA(temp, slice, scaleY, coeffs, offset, filterLength)
}()
}
wg.Wait()
return result
case *image.NRGBA:
// 8-bit precision
temp := image.NewNRGBA(image.Rect(0, 0, input.Bounds().Dy(), int(width)))
result := image.NewNRGBA(image.Rect(0, 0, int(width), int(height)))
temp := image.NewRGBA(image.Rect(0, 0, input.Bounds().Dy(), int(width)))
result := image.NewRGBA(image.Rect(0, 0, int(width), int(height)))
// horizontal filter, results in transposed temporary image
coeffs, offset, filterLength := createWeights8(temp.Bounds().Dy(), taps, blur, scaleX, kernel)
wg.Add(cpus)
for i := 0; i < cpus; i++ {
slice := makeSlice(temp, i, cpus).(*image.NRGBA)
slice := makeSlice(temp, i, cpus).(*image.RGBA)
go func() {
defer wg.Done()
resizeNRGBA(input, slice, scaleX, coeffs, offset, filterLength)
@ -153,10 +153,10 @@ func Resize(width, height uint, img image.Image, interp InterpolationFunction) i
coeffs, offset, filterLength = createWeights8(result.Bounds().Dy(), taps, blur, scaleY, kernel)
wg.Add(cpus)
for i := 0; i < cpus; i++ {
slice := makeSlice(result, i, cpus).(*image.NRGBA)
slice := makeSlice(result, i, cpus).(*image.RGBA)
go func() {
defer wg.Done()
resizeNRGBA(temp, slice, scaleY, coeffs, offset, filterLength)
resizeRGBA(temp, slice, scaleY, coeffs, offset, filterLength)
}()
}
wg.Wait()
@ -194,14 +194,14 @@ func Resize(width, height uint, img image.Image, interp InterpolationFunction) i
return result.YCbCr()
case *image.RGBA64:
// 16-bit precision
temp := image.NewNRGBA64(image.Rect(0, 0, input.Bounds().Dy(), int(width)))
result := image.NewNRGBA64(image.Rect(0, 0, int(width), int(height)))
temp := image.NewRGBA64(image.Rect(0, 0, input.Bounds().Dy(), int(width)))
result := image.NewRGBA64(image.Rect(0, 0, int(width), int(height)))
// horizontal filter, results in transposed temporary image
coeffs, offset, filterLength := createWeights16(temp.Bounds().Dy(), taps, blur, scaleX, kernel)
wg.Add(cpus)
for i := 0; i < cpus; i++ {
slice := makeSlice(temp, i, cpus).(*image.NRGBA64)
slice := makeSlice(temp, i, cpus).(*image.RGBA64)
go func() {
defer wg.Done()
resizeRGBA64(input, slice, scaleX, coeffs, offset, filterLength)
@ -213,24 +213,24 @@ func Resize(width, height uint, img image.Image, interp InterpolationFunction) i
coeffs, offset, filterLength = createWeights16(result.Bounds().Dy(), taps, blur, scaleY, kernel)
wg.Add(cpus)
for i := 0; i < cpus; i++ {
slice := makeSlice(result, i, cpus).(*image.NRGBA64)
slice := makeSlice(result, i, cpus).(*image.RGBA64)
go func() {
defer wg.Done()
resizeNRGBA64(temp, slice, scaleY, coeffs, offset, filterLength)
resizeRGBA64(temp, slice, scaleY, coeffs, offset, filterLength)
}()
}
wg.Wait()
return result
case *image.NRGBA64:
// 16-bit precision
temp := image.NewNRGBA64(image.Rect(0, 0, input.Bounds().Dy(), int(width)))
result := image.NewNRGBA64(image.Rect(0, 0, int(width), int(height)))
temp := image.NewRGBA64(image.Rect(0, 0, input.Bounds().Dy(), int(width)))
result := image.NewRGBA64(image.Rect(0, 0, int(width), int(height)))
// horizontal filter, results in transposed temporary image
coeffs, offset, filterLength := createWeights16(temp.Bounds().Dy(), taps, blur, scaleX, kernel)
wg.Add(cpus)
for i := 0; i < cpus; i++ {
slice := makeSlice(temp, i, cpus).(*image.NRGBA64)
slice := makeSlice(temp, i, cpus).(*image.RGBA64)
go func() {
defer wg.Done()
resizeNRGBA64(input, slice, scaleX, coeffs, offset, filterLength)
@ -242,10 +242,10 @@ func Resize(width, height uint, img image.Image, interp InterpolationFunction) i
coeffs, offset, filterLength = createWeights16(result.Bounds().Dy(), taps, blur, scaleY, kernel)
wg.Add(cpus)
for i := 0; i < cpus; i++ {
slice := makeSlice(result, i, cpus).(*image.NRGBA64)
slice := makeSlice(result, i, cpus).(*image.RGBA64)
go func() {
defer wg.Done()
resizeNRGBA64(temp, slice, scaleY, coeffs, offset, filterLength)
resizeRGBA64(temp, slice, scaleY, coeffs, offset, filterLength)
}()
}
wg.Wait()
@ -310,14 +310,14 @@ func Resize(width, height uint, img image.Image, interp InterpolationFunction) i
return result
default:
// 16-bit precision
temp := image.NewNRGBA64(image.Rect(0, 0, img.Bounds().Dy(), int(width)))
result := image.NewNRGBA64(image.Rect(0, 0, int(width), int(height)))
temp := image.NewRGBA64(image.Rect(0, 0, img.Bounds().Dy(), int(width)))
result := image.NewRGBA64(image.Rect(0, 0, int(width), int(height)))
// horizontal filter, results in transposed temporary image
coeffs, offset, filterLength := createWeights16(temp.Bounds().Dy(), taps, blur, scaleX, kernel)
wg.Add(cpus)
for i := 0; i < cpus; i++ {
slice := makeSlice(temp, i, cpus).(*image.NRGBA64)
slice := makeSlice(temp, i, cpus).(*image.RGBA64)
go func() {
defer wg.Done()
resizeGeneric(img, slice, scaleX, coeffs, offset, filterLength)
@ -329,10 +329,10 @@ func Resize(width, height uint, img image.Image, interp InterpolationFunction) i
coeffs, offset, filterLength = createWeights16(result.Bounds().Dy(), taps, blur, scaleY, kernel)
wg.Add(cpus)
for i := 0; i < cpus; i++ {
slice := makeSlice(result, i, cpus).(*image.NRGBA64)
slice := makeSlice(result, i, cpus).(*image.RGBA64)
go func() {
defer wg.Done()
resizeNRGBA64(temp, slice, scaleY, coeffs, offset, filterLength)
resizeRGBA64(temp, slice, scaleY, coeffs, offset, filterLength)
}()
}
wg.Wait()

12
resize_test.go
View File

@ -56,7 +56,7 @@ func Test_SameColorWithRGBA(t *testing.T) {
out := Resize(10, 10, img, Lanczos3)
for y := out.Bounds().Min.Y; y < out.Bounds().Max.Y; y++ {
for x := out.Bounds().Min.X; x < out.Bounds().Max.X; x++ {
color := out.At(x, y).(color.NRGBA)
color := out.At(x, y).(color.RGBA)
if color.R != 0x80 || color.G != 0x80 || color.B != 0x80 || color.A != 0xFF {
t.Errorf("%+v", color)
}
@ -74,7 +74,7 @@ func Test_SameColorWithNRGBA(t *testing.T) {
out := Resize(10, 10, img, Lanczos3)
for y := out.Bounds().Min.Y; y < out.Bounds().Max.Y; y++ {
for x := out.Bounds().Min.X; x < out.Bounds().Max.X; x++ {
color := out.At(x, y).(color.NRGBA)
color := out.At(x, y).(color.RGBA)
if color.R != 0x80 || color.G != 0x80 || color.B != 0x80 || color.A != 0xFF {
t.Errorf("%+v", color)
}
@ -92,7 +92,7 @@ func Test_SameColorWithRGBA64(t *testing.T) {
out := Resize(10, 10, img, Lanczos3)
for y := out.Bounds().Min.Y; y < out.Bounds().Max.Y; y++ {
for x := out.Bounds().Min.X; x < out.Bounds().Max.X; x++ {
color := out.At(x, y).(color.NRGBA64)
color := out.At(x, y).(color.RGBA64)
if color.R != 0x8000 || color.G != 0x8000 || color.B != 0x8000 || color.A != 0xFFFF {
t.Errorf("%+v", color)
}
@ -110,7 +110,7 @@ func Test_SameColorWithNRGBA64(t *testing.T) {
out := Resize(10, 10, img, Lanczos3)
for y := out.Bounds().Min.Y; y < out.Bounds().Max.Y; y++ {
for x := out.Bounds().Min.X; x < out.Bounds().Max.X; x++ {
color := out.At(x, y).(color.NRGBA64)
color := out.At(x, y).(color.RGBA64)
if color.R != 0x8000 || color.G != 0x8000 || color.B != 0x8000 || color.A != 0xFFFF {
t.Errorf("%+v", color)
}
@ -204,8 +204,8 @@ func Test_ResizeWithPremultipliedAlpha(t *testing.T) {
out := Resize(1, 2, img, MitchellNetravali)
outputColor := out.At(0, 0).(color.NRGBA)
if outputColor.R != 0xFF {
outputColor := out.At(0, 0).(color.RGBA)
if outputColor.R != 0x80 {
t.Fail()
}
}