Rename Lanczos functions using look-up tables to Lanczos2Lut, Lanczos3Lut and restore Lanczos2, Lanczos3 to give users the choice between higher speed or higher accuracy.
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16
filters.go
16
filters.go
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@ -209,8 +209,6 @@ func MitchellNetravali(img image.Image, factor [2]float32) Filter {
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}
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func splineKernel(B, C float32) func(float32) float32 {
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const lanczosTableSize = 300
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factorA := 2.0 - 1.5*B - C
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factorB := -3.0 + 2.0*B + C
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factorC := 1.0 - 1.0/3.0*B
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@ -244,14 +242,28 @@ func lanczosKernel(a uint) func(float32) float32 {
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}
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}
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const lanczosTableSize = 300
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// Lanczos interpolation (a=2)
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func Lanczos2(img image.Image, factor [2]float32) Filter {
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return createFilter(img, factor, 4, lanczosKernel(2))
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}
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// Lanczos interpolation (a=2) using a look-up table
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// to speed up computation
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func Lanczos2Lut(img image.Image, factor [2]float32) Filter {
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return createFilter(img, factor, 4,
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tableKernel(lanczosKernel(2), lanczosTableSize, 2.0))
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}
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// Lanczos interpolation (a=3)
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func Lanczos3(img image.Image, factor [2]float32) Filter {
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return createFilter(img, factor, 6, lanczosKernel(3))
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}
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// Lanczos interpolation (a=3) using a look-up table
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// to speed up computation
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func Lanczos3Lut(img image.Image, factor [2]float32) Filter {
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return createFilter(img, factor, 6,
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tableKernel(lanczosKernel(3), lanczosTableSize, 3.0))
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}
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