aw/go-resize
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Kernel simplified

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This commit is contained in:
jst 2012-09-15 19:30:32 +02:00
parent eaf9383af0
commit 3fc31c95cc
2 changed files with 24 additions and 23 deletions
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45
filters.go
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@ -23,12 +23,12 @@ import (
) )
// color.RGBA64 as array // color.RGBA64 as array
type RGBA [4]uint16 type rgba16 [4]uint16
// build RGBA from an arbitrary color // build RGBA from an arbitrary color
func toRGBA(c color.Color) RGBA { func toRGBA(c color.Color) rgba16 {
r, g, b, a := c.RGBA() r, g, b, a := c.RGBA()
return RGBA{uint16(r), uint16(g), uint16(b), uint16(a)} return rgba16{uint16(r), uint16(g), uint16(b), uint16(a)}
} }
func clampToUint16(x float32) (y uint16) { func clampToUint16(x float32) (y uint16) {
@ -41,15 +41,17 @@ func clampToUint16(x float32) (y uint16) {
return return
} }
func convolution1d(x float32, kernel func(float32, int) float32, p []RGBA) (c RGBA) { func convolution1d(x float32, kernel func(float32) float32, p []rgba16) (c rgba16) {
x -= float32(int(x)) x -= float32(int(x))
m := float32(len(p)/2-1)
var k float32 var k float32
var sum float32 = 0 var sum float32 = 0
l := [4]float32{0.0, 0.0, 0.0, 0.0} l := [4]float32{0.0, 0.0, 0.0, 0.0}
for j := range p { for j := range p {
k = kernel(x, j) k = kernel(x+m-float32(j))
sum += k sum += k
for i := range c { for i := range c {
l[i] += float32(p[j][i]) * k l[i] += float32(p[j][i]) * k
@ -61,11 +63,11 @@ func convolution1d(x float32, kernel func(float32, int) float32, p []RGBA) (c RG
return return
} }
func filter(x, y float32, img image.Image, n int, kernel func(x float32, j int) float32) color.RGBA64 { func filter(x, y float32, img image.Image, n int, kernel func(x float32) float32) color.RGBA64 {
xf, yf := int(x)-n/2+1, int(y)-n/2+1 xf, yf := int(x)-n/2+1, int(y)-n/2+1
row := make([]RGBA, n) row := make([]rgba16, n)
col := make([]RGBA, n) col := make([]rgba16, n)
for i := 0; i < n; i++ { for i := 0; i < n; i++ {
for j := 0; j < n; j++ { for j := 0; j < n; j++ {
@ -82,8 +84,8 @@ func filter(x, y float32, img image.Image, n int, kernel func(x float32, j int)
// Approximates a value by returning the value of the nearest point. // Approximates a value by returning the value of the nearest point.
func NearestNeighbor(x, y float32, img image.Image) color.RGBA64 { func NearestNeighbor(x, y float32, img image.Image) color.RGBA64 {
n := 2 n := 2
kernel := func(x float32, j int) (y float32) { kernel := func(x float32) (y float32) {
if x+0.5 >= float32(j) && x+0.5 < float32(j)+1 { if x >= -0.5 && x < 0.5 {
y = 1 y = 1
} else { } else {
y = 0 y = 0
@ -96,9 +98,8 @@ func NearestNeighbor(x, y float32, img image.Image) color.RGBA64 {
// Bicubic interpolation // Bicubic interpolation
func Bilinear(x, y float32, img image.Image) color.RGBA64 { func Bilinear(x, y float32, img image.Image) color.RGBA64 {
n := 2 n := 2
kernel := func(x float32, j int) float32 { kernel := func(x float32) float32 {
xa := float32(math.Abs(float64(x - float32(j)))) return 1 - float32(math.Abs(float64(x)))
return 1 - xa
} }
return filter(x, y, img, n, kernel) return filter(x, y, img, n, kernel)
} }
@ -106,12 +107,12 @@ func Bilinear(x, y float32, img image.Image) color.RGBA64 {
// Bicubic interpolation // Bicubic interpolation
func Bicubic(x, y float32, img image.Image) color.RGBA64 { func Bicubic(x, y float32, img image.Image) color.RGBA64 {
n := 4 n := 4
kernel := func(x float32, j int) (y float32) { kernel := func(x float32) (y float32) {
xa := float32(math.Abs(float64(x - float32(j-1)))) absX := float32(math.Abs(float64(x)))
if xa <= 1 { if absX <= 1 {
y = 1.5*xa*xa*xa - 2.5*xa*xa + 1 y = absX*absX*(1.5*absX-2.5) + 1
} else { } else {
y = -0.5*xa*xa*xa + 2.5*xa*xa - 4*xa + 2 y = absX*(absX*(2.5-0.5*absX)-4) + 2
} }
return return
} }
@ -121,8 +122,8 @@ func Bicubic(x, y float32, img image.Image) color.RGBA64 {
// Lanczos interpolation (a=2). // Lanczos interpolation (a=2).
func Lanczos2(x, y float32, img image.Image) color.RGBA64 { func Lanczos2(x, y float32, img image.Image) color.RGBA64 {
n := 4 n := 4
kernel := func(x float32, j int) float32 { kernel := func(x float32) float32 {
return float32(Sinc(float64(x-float32(j-1)))) * float32(Sinc(float64((x-float32(j-1))/float32(2)))) return float32(Sinc(float64(x))) * float32(Sinc(float64((x)/float32(2))))
} }
return filter(x, y, img, n, kernel) return filter(x, y, img, n, kernel)
} }
@ -130,8 +131,8 @@ func Lanczos2(x, y float32, img image.Image) color.RGBA64 {
// Lanczos interpolation (a=3). // Lanczos interpolation (a=3).
func Lanczos3(x, y float32, img image.Image) color.RGBA64 { func Lanczos3(x, y float32, img image.Image) color.RGBA64 {
n := 6 n := 6
kernel := func(x float32, j int) float32 { kernel := func(x float32) float32 {
return float32(Sinc(float64(x-float32(j-2)))) * float32(Sinc(float64((x-float32(j-2))/float32(3)))) return float32(Sinc(float64(x))) * float32(Sinc(float64((x)/float32(3))))
} }
return filter(x, y, img, n, kernel) return filter(x, y, img, n, kernel)
} }

2
resize_test.go
View File

@ -14,7 +14,7 @@ func init() {
func Test_Nearest(t *testing.T) { func Test_Nearest(t *testing.T) {
m := Resize(6, 0, img, NearestNeighbor) m := Resize(6, 0, img, NearestNeighbor)
if m.At(2, 2) != m.At(3, 3) { if m.At(2, 2) == m.At(3, 3) {
t.Fail() t.Fail()
} }
} }