aw/go-resize
1
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

initial commit

Browse Source
This commit is contained in:
nfnt 2012-08-02 21:59:40 +02:00
commit 428642c9f1
6 changed files with 355 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

0
README Normal file
View File

142
filters.go Normal file
View File

@ -0,0 +1,142 @@
/*
Copyright (c) 2012, Jan Schlicht <jan.schlicht@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"
"math"
)
// color.RGBA64 as array
type RGBA [4]uint16
// build RGBA from an arbitrary color
func toRGBA(c color.Color) RGBA {
n := color.RGBA64Model.Convert(c).(color.RGBA64)
return RGBA{n.R, n.G, n.B, n.A}
}
func clampToUint16(x float32) (y uint16) {
y = uint16(x)
if x < 0 {
y = 0
} else if x > float32(0xffff) {
y = 0xffff
}
return
}
// Nearest-neighbor interpolation.
// Approximates a value by returning the value of the nearest point.
func NearestNeighbor(x, y float32, img image.Image) color.RGBA64 {
xn, yn := int(x), int(y)
c := toRGBA(img.At(xn, yn))
return color.RGBA64{c[0], c[1], c[2], c[3]}
}
// Linear interpolation.
func linearInterp(x float32, p *[2]RGBA) (c RGBA) {
x -= float32(math.Floor(float64(x)))
for i := range c {
c[i] = clampToUint16(float32(p[0][i])*(1.0-x) + x*float32(p[1][i]))
}
return
}
// Bilinear interpolation.
func Bilinear(x, y float32, img image.Image) color.RGBA64 {
xf, yf := int(math.Floor(float64(x))), int(math.Floor(float64(y)))
var row [2]RGBA
var col [2]RGBA
row = [2]RGBA{toRGBA(img.At(xf, yf)), toRGBA(img.At(xf+1, yf))}
col[0] = linearInterp(x, &row)
row = [2]RGBA{toRGBA(img.At(xf, yf+1)), toRGBA(img.At(xf+1, yf+1))}
col[1] = linearInterp(x, &row)
c := linearInterp(y, &col)
return color.RGBA64{c[0], c[1], c[2], c[3]}
}
// cubic interpolation
func cubicInterp(x float32, p *[4]RGBA) (c RGBA) {
x -= float32(math.Floor(float64(x)))
for i := range c {
c[i] = clampToUint16(float32(p[1][i]) + 0.5*x*(float32(p[2][i])-float32(p[0][i])+x*(2.0*float32(p[0][i])-5.0*float32(p[1][i])+4.0*float32(p[2][i])-float32(p[3][i])+x*(3.0*(float32(p[1][i])-float32(p[2][i]))+float32(p[3][i])-float32(p[0][i])))))
}
return
}
// Bicubic interpolation.
func Bicubic(x, y float32, img image.Image) color.RGBA64 {
xf, yf := int(math.Floor(float64(x))), int(math.Floor(float64(y)))
var row [4]RGBA
var col [4]RGBA
row = [4]RGBA{toRGBA(img.At(xf-1, yf-1)), toRGBA(img.At(xf, yf-1)), toRGBA(img.At(xf+1, yf-1)), toRGBA(img.At(xf+2, yf-1))}
col[0] = cubicInterp(x, &row)
row = [4]RGBA{toRGBA(img.At(xf-1, yf)), toRGBA(img.At(xf, yf)), toRGBA(img.At(xf+1, yf)), toRGBA(img.At(xf+2, yf))}
col[1] = cubicInterp(x, &row)
row = [4]RGBA{toRGBA(img.At(xf-1, yf+1)), toRGBA(img.At(xf, yf+1)), toRGBA(img.At(xf+1, yf+1)), toRGBA(img.At(xf+2, yf+1))}
col[2] = cubicInterp(x, &row)
row = [4]RGBA{toRGBA(img.At(xf-1, yf+2)), toRGBA(img.At(xf, yf+2)), toRGBA(img.At(xf+1, yf+2)), toRGBA(img.At(xf+2, yf+2))}
col[3] = cubicInterp(x, &row)
c := cubicInterp(y, &col)
return color.RGBA64{c[0], c[1], c[2], c[3]}
}
// 1-d convolution with windowed sinc for a=3.
func lanczos_x(x float32, p *[6]RGBA) (c RGBA) {
x -= float32(math.Floor(float64(x)))
var v float32
l := [4]float32{0.0, 0.0, 0.0, 0.0}
for j := range p {
v = float32(Sinc(float64(x-float32(j-2)))) * float32(Sinc(float64((x-float32(j-2))/3.0)))
for i := range c {
l[i] += float32(p[j][i]) * v
}
}
for i := range c {
c[i] = clampToUint16(l[i])
}
return
}
// Lanczos interpolation (a=3).
func Lanczos3(x, y float32, img image.Image) color.RGBA64 {
xf, yf := int(math.Floor(float64(x))), int(math.Floor(float64(y)))
var row [6]RGBA
var col [6]RGBA
row = [6]RGBA{toRGBA(img.At(xf-2, yf-2)), toRGBA(img.At(xf-1, yf-2)), toRGBA(img.At(xf, yf-2)), toRGBA(img.At(xf+1, yf-2)), toRGBA(img.At(xf+2, yf-2)), toRGBA(img.At(xf+3, yf-2))}
col[0] = lanczos_x(x, &row)
row = [6]RGBA{toRGBA(img.At(xf-2, yf-1)), toRGBA(img.At(xf-1, yf-1)), toRGBA(img.At(xf, yf-1)), toRGBA(img.At(xf+1, yf-1)), toRGBA(img.At(xf+2, yf-1)), toRGBA(img.At(xf+3, yf-1))}
col[1] = lanczos_x(x, &row)
row = [6]RGBA{toRGBA(img.At(xf-2, yf)), toRGBA(img.At(xf-1, yf)), toRGBA(img.At(xf, yf)), toRGBA(img.At(xf+1, yf)), toRGBA(img.At(xf+2, yf)), toRGBA(img.At(xf+3, yf))}
col[2] = lanczos_x(x, &row)
row = [6]RGBA{toRGBA(img.At(xf-2, yf+1)), toRGBA(img.At(xf-1, yf+1)), toRGBA(img.At(xf, yf+1)), toRGBA(img.At(xf+1, yf+1)), toRGBA(img.At(xf+2, yf+1)), toRGBA(img.At(xf+3, yf+1))}
col[3] = lanczos_x(x, &row)
row = [6]RGBA{toRGBA(img.At(xf-2, yf+2)), toRGBA(img.At(xf-1, yf+2)), toRGBA(img.At(xf, yf+2)), toRGBA(img.At(xf+1, yf+2)), toRGBA(img.At(xf+2, yf+2)), toRGBA(img.At(xf+3, yf+2))}
col[4] = lanczos_x(x, &row)
row = [6]RGBA{toRGBA(img.At(xf-2, yf+3)), toRGBA(img.At(xf-1, yf+3)), toRGBA(img.At(xf, yf+3)), toRGBA(img.At(xf+1, yf+3)), toRGBA(img.At(xf+2, yf+3)), toRGBA(img.At(xf+3, yf+3))}
col[5] = lanczos_x(x, &row)
c := lanczos_x(y, &col)
return color.RGBA64{c[0], c[1], c[2], c[3]}
}

108
resize.go Normal file
View File

@ -0,0 +1,108 @@
/*
Copyright (c) 2012, Jan Schlicht <jan.schlicht@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 implements various image resizing methods.
//
// The package works with the Image interface described in the image package.
// Various interpolation methods are provided and multiple processors may be
// utilized in the computations.
//
// Example:
// imgResized := resize.Resize(1000, -1, imgOld, Lanczos3)
package resize
import (
"image"
"image/color"
"runtime"
)
var (
// NCPU holds the number of available CPUs at runtime.
NCPU = runtime.NumCPU()
)
// Trans2 is a 2-dimensional linear transformation.
type Trans2 [6]float32
// Apply the transformation to a point (x,y).
func (t *Trans2) Eval(x, y float32) (u, v float32) {
u = t[0]*x + t[1]*y + t[2]
v = t[3]*x + t[4]*y + t[5]
return
}
// Calculate scaling factors using old and new image dimensions.
func calcFactors(w, h int, wo, ho float32) (sx, sy float32) {
if w == -1 {
if h == -1 {
sx = 1.0
sy = 1.0
} else {
sy = ho / float32(h)
sx = sy
}
} else {
sx = wo / float32(w)
if h == -1 {
sy = sx
} else {
sy = ho / float32(h)
}
}
return
}
// InterpolationFunction return a color for an arbitrary point inside
// an image
type InterpolationFunction func(float32, float32, image.Image) color.RGBA64
// Resize an image to new width w and height h using the interpolation function interp.
// A new image with the given dimensions will be returned.
// If one of the parameters w or h is set to -1, its size will be calculated so that
// the aspect ratio is that of the originating image.
// The resizing algorithm uses slices for parallel computation.
func Resize(w int, h int, img image.Image, interp InterpolationFunction) image.Image {
b_old := img.Bounds()
w_old := float32(b_old.Dx())
h_old := float32(b_old.Dy())
scaleX, scaleY := calcFactors(w, h, w_old, h_old)
t := Trans2{scaleX, 0, float32(b_old.Min.X), 0, scaleY, float32(b_old.Min.Y)}
m := image.NewRGBA64(image.Rect(0, 0, int(w_old/scaleX), int(h_old/scaleY)))
b := m.Bounds()
c := make(chan int, NCPU)
for i := 0; i < NCPU; i++ {
go func(b image.Rectangle, c chan int) {
var u, v float32
for y := b.Min.Y; y < b.Max.Y; y++ {
for x := b.Min.X; x < b.Max.X; x++ {
u, v = t.Eval(float32(x), float32(y))
m.SetRGBA64(x, y, interp(u, v, img))
}
}
c <- 1
}(image.Rect(b.Min.X, b.Min.Y+i*(b.Dy())/4, b.Max.X, b.Min.Y+(i+1)*(b.Dy())/4), c)
}
for i := 0; i < NCPU; i++ {
<-c
}
return m
}

18
resize_test.go Normal file
View File

@ -0,0 +1,18 @@
package resize
import (
"image"
"image/color"
"testing"
)
func Test_Nearest(t *testing.T) {
img := image.NewGray16(image.Rect(0,0, 3,3))
img.Set(1,1, color.White)
m := Resize(6,-1, img, NearestNeighbor)
if m.At(2,2) != m.At(3,3) {
t.Fail()
}
}

49
sinc.go Normal file
View File

@ -0,0 +1,49 @@
/*
Copyright (c) 2012, Jan Schlicht <jan.schlicht@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 (
"math"
)
var (
epsilon = math.Nextafter(1.0, 2.0) - 1.0 // machine epsilon
taylor2bound = math.Sqrt(epsilon)
taylorNbound = math.Sqrt(taylor2bound)
)
// unnormalized sinc function
func Sinc1(x float64) (y float64) {
if math.Abs(x) >= taylorNbound {
y = math.Sin(x) / x
} else {
y = 1.0
if math.Abs(x) >= epsilon {
x2 := x * x
y -= x2 / 6.0
if math.Abs(x) >= taylor2bound {
y += (x2 * x2) / 120.0
}
}
}
return
}
// normalized sinc function
func Sinc(x float64) float64 {
return Sinc1(x * math.Pi)
}

38
sinc_test.go Normal file
View File

@ -0,0 +1,38 @@
package resize
import (
"fmt"
"math"
"testing"
)
const limit = 1e-12
func Test_SincOne(t *testing.T) {
zero := Sinc(1)
if zero >= limit {
t.Error("Sinc(1) != 0")
}
}
func Test_SincZero(t *testing.T) {
one := Sinc(0)
if math.Abs(one-1) >= limit {
t.Error("Sinc(0) != 1")
}
}
func Test_SincDotOne(t *testing.T) {
res := Sinc(0.1)
if math.Abs(res-0.983631643083466) >= limit {
t.Error("Sinc(0.1) wrong")
}
}
func Test_SincNearZero(t *testing.T) {
res := Sinc(0.000001)
if math.Abs(res-0.9999999999983551) >= limit {
fmt.Println(res)
t.Error("Sinc near zero not stable")
}
}