Kernel simplified
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parent
eaf9383af0
commit
3fc31c95cc
45
filters.go
45
filters.go
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@ -23,12 +23,12 @@ import (
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)
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// color.RGBA64 as array
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type RGBA [4]uint16
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type rgba16 [4]uint16
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// build RGBA from an arbitrary color
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func toRGBA(c color.Color) RGBA {
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func toRGBA(c color.Color) rgba16 {
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r, g, b, a := c.RGBA()
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return RGBA{uint16(r), uint16(g), uint16(b), uint16(a)}
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return rgba16{uint16(r), uint16(g), uint16(b), uint16(a)}
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}
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func clampToUint16(x float32) (y uint16) {
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@ -41,15 +41,17 @@ func clampToUint16(x float32) (y uint16) {
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return
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}
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func convolution1d(x float32, kernel func(float32, int) float32, p []RGBA) (c RGBA) {
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func convolution1d(x float32, kernel func(float32) float32, p []rgba16) (c rgba16) {
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x -= float32(int(x))
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m := float32(len(p)/2-1)
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var k float32
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var sum float32 = 0
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l := [4]float32{0.0, 0.0, 0.0, 0.0}
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for j := range p {
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k = kernel(x, j)
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k = kernel(x+m-float32(j))
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sum += k
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for i := range c {
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l[i] += float32(p[j][i]) * k
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@ -61,11 +63,11 @@ func convolution1d(x float32, kernel func(float32, int) float32, p []RGBA) (c RG
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return
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}
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func filter(x, y float32, img image.Image, n int, kernel func(x float32, j int) float32) color.RGBA64 {
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func filter(x, y float32, img image.Image, n int, kernel func(x float32) float32) color.RGBA64 {
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xf, yf := int(x)-n/2+1, int(y)-n/2+1
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row := make([]RGBA, n)
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col := make([]RGBA, n)
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row := make([]rgba16, n)
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col := make([]rgba16, n)
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for i := 0; i < n; i++ {
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for j := 0; j < n; j++ {
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@ -82,8 +84,8 @@ func filter(x, y float32, img image.Image, n int, kernel func(x float32, j int)
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// Approximates a value by returning the value of the nearest point.
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func NearestNeighbor(x, y float32, img image.Image) color.RGBA64 {
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n := 2
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kernel := func(x float32, j int) (y float32) {
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if x+0.5 >= float32(j) && x+0.5 < float32(j)+1 {
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kernel := func(x float32) (y float32) {
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if x >= -0.5 && x < 0.5 {
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y = 1
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} else {
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y = 0
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@ -96,9 +98,8 @@ func NearestNeighbor(x, y float32, img image.Image) color.RGBA64 {
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// Bicubic interpolation
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func Bilinear(x, y float32, img image.Image) color.RGBA64 {
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n := 2
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kernel := func(x float32, j int) float32 {
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xa := float32(math.Abs(float64(x - float32(j))))
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return 1 - xa
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kernel := func(x float32) float32 {
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return 1 - float32(math.Abs(float64(x)))
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}
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return filter(x, y, img, n, kernel)
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}
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@ -106,12 +107,12 @@ func Bilinear(x, y float32, img image.Image) color.RGBA64 {
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// Bicubic interpolation
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func Bicubic(x, y float32, img image.Image) color.RGBA64 {
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n := 4
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kernel := func(x float32, j int) (y float32) {
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xa := float32(math.Abs(float64(x - float32(j-1))))
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if xa <= 1 {
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y = 1.5*xa*xa*xa - 2.5*xa*xa + 1
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kernel := func(x float32) (y float32) {
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absX := float32(math.Abs(float64(x)))
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if absX <= 1 {
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y = absX*absX*(1.5*absX-2.5) + 1
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} else {
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y = -0.5*xa*xa*xa + 2.5*xa*xa - 4*xa + 2
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y = absX*(absX*(2.5-0.5*absX)-4) + 2
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}
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return
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}
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@ -121,8 +122,8 @@ func Bicubic(x, y float32, img image.Image) color.RGBA64 {
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// Lanczos interpolation (a=2).
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func Lanczos2(x, y float32, img image.Image) color.RGBA64 {
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n := 4
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kernel := func(x float32, j int) float32 {
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return float32(Sinc(float64(x-float32(j-1)))) * float32(Sinc(float64((x-float32(j-1))/float32(2))))
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kernel := func(x float32) float32 {
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return float32(Sinc(float64(x))) * float32(Sinc(float64((x)/float32(2))))
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}
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return filter(x, y, img, n, kernel)
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}
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@ -130,8 +131,8 @@ func Lanczos2(x, y float32, img image.Image) color.RGBA64 {
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// Lanczos interpolation (a=3).
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func Lanczos3(x, y float32, img image.Image) color.RGBA64 {
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n := 6
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kernel := func(x float32, j int) float32 {
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return float32(Sinc(float64(x-float32(j-2)))) * float32(Sinc(float64((x-float32(j-2))/float32(3))))
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kernel := func(x float32) float32 {
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return float32(Sinc(float64(x))) * float32(Sinc(float64((x)/float32(3))))
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}
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return filter(x, y, img, n, kernel)
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}
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@ -14,7 +14,7 @@ func init() {
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func Test_Nearest(t *testing.T) {
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m := Resize(6, 0, img, NearestNeighbor)
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if m.At(2, 2) != m.At(3, 3) {
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if m.At(2, 2) == m.At(3, 3) {
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t.Fail()
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}
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}
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