Multiply instead of dividing
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parent
314cea6612
commit
45368ad0cd
20
filters.go
20
filters.go
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@ -42,7 +42,7 @@ type filterModel struct {
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// instead of blurring an image before downscaling to avoid aliasing,
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// the filter is scaled by a factor which leads to a similar effect
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factor float32
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factorInv float32
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// for optimized access to image points
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converter
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@ -51,12 +51,12 @@ type filterModel struct {
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tempRow []colorArray
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}
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func (f *filterModel) convolution1d(x float32, p []colorArray, factor float32) (c colorArray) {
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func (f *filterModel) convolution1d(x float32, p []colorArray) (c colorArray) {
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var k float32
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var sum float32 = 0
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for j := range p {
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k = f.kernel((x - float32(j)) / factor)
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k = f.kernel((x - float32(j)) * f.factorInv)
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sum += k
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for i := range c {
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c[i] += p[j][i] * k
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@ -79,7 +79,7 @@ func (f *filterModel) Interpolate(u float32, y int) color.RGBA64 {
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f.at(uf+i, y, &f.tempRow[i])
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}
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c := f.convolution1d(u, f.tempRow, f.factor)
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c := f.convolution1d(u, f.tempRow)
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return color.RGBA64{
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clampToUint16(c[0]),
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clampToUint16(c[1]),
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@ -96,37 +96,37 @@ func createFilter(img image.Image, factor float32, size int, kernel func(float32
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switch img.(type) {
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default:
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f = &filterModel{
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kernel, factor,
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kernel, 1. / factor,
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&genericConverter{img},
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make([]colorArray, sizeX),
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}
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case *image.RGBA:
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f = &filterModel{
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kernel, factor,
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kernel, 1. / factor,
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&rgbaConverter{img.(*image.RGBA)},
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make([]colorArray, sizeX),
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}
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case *image.RGBA64:
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f = &filterModel{
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kernel, factor,
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kernel, 1. / factor,
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&rgba64Converter{img.(*image.RGBA64)},
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make([]colorArray, sizeX),
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}
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case *image.Gray:
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f = &filterModel{
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kernel, factor,
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kernel, 1. / factor,
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&grayConverter{img.(*image.Gray)},
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make([]colorArray, sizeX),
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}
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case *image.Gray16:
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f = &filterModel{
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kernel, factor,
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kernel, 1. / factor,
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&gray16Converter{img.(*image.Gray16)},
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make([]colorArray, sizeX),
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}
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case *image.YCbCr:
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f = &filterModel{
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kernel, factor,
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kernel, 1. / factor,
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&ycbcrConverter{img.(*image.YCbCr)},
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make([]colorArray, sizeX),
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}
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