aw/go-resize
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Make kernel the only dependency of convolution1d

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This commit is contained in:
jst 2012-12-13 22:13:37 +01:00
parent e512502b3c
commit 82ab8b977c
1 changed files with 5 additions and 17 deletions
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22
filters.go
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@ -35,23 +35,13 @@ func clampToUint16(x float32) (y uint16) {
return
}
func boolToUint(b bool) (i uint) {
if b {
i = 1
} else {
i = 0
}
return
}
// describe a resampling filter
type filterModel struct {
// resampling is done by convolution with a (scaled) kernel
kernel func(float32) float32
// instead of blurring an image before downscaling to avoid aliasing,
// to filter is scaled by a factor which leads to a similar effect
// the filter is scaled by a factor which leads to a similar effect
factor [2]float32
// for optimized access to image points
@ -61,15 +51,13 @@ type filterModel struct {
tempRow, tempCol []colorArray
}
func (f *filterModel) convolution1d(x float32, p []colorArray, isCol bool) colorArray {
func (f *filterModel) convolution1d(x float32, p []colorArray, factor float32) colorArray {
var k float32
var sum float32 = 0
c := colorArray{0.0, 0.0, 0.0, 0.0}
index := boolToUint(isCol)
for j := range p {
k = f.kernel((x - float32(j)) / f.factor[index])
k = f.kernel((x - float32(j)) / factor)
sum += k
for i := range c {
c[i] += p[j][i] * k
@ -94,10 +82,10 @@ func (f *filterModel) Interpolate(x, y float32) color.RGBA64 {
f.tempRow[j] = f.at(xf+j, yf+i)
}
f.tempCol[i] = f.convolution1d(x, f.tempRow, false)
f.tempCol[i] = f.convolution1d(x, f.tempRow, f.factor[0])
}
c := f.convolution1d(y, f.tempCol, true)
c := f.convolution1d(y, f.tempCol, f.factor[1])
return color.RGBA64{
clampToUint16(c[0]),
clampToUint16(c[1]),