Reverse alpha-premultiplication for image.RGBA, image.RGBA64 and generic images
types.
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parent
5a6676c19e
commit
c3c062672a
59
converter.go
59
converter.go
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@ -64,6 +64,17 @@ func resizeGeneric(in image.Image, out *image.NRGBA64, scale float64, coeffs []i
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xi = maxX
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xi = maxX
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}
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}
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r, g, b, a := in.At(xi+in.Bounds().Min.X, x+in.Bounds().Min.Y).RGBA()
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r, g, b, a := in.At(xi+in.Bounds().Min.X, x+in.Bounds().Min.Y).RGBA()
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// reverse alpha-premultiplication.
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if a != 0 {
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r *= 0xffff
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r /= a
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g *= 0xffff
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g /= a
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b *= 0xffff
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b /= a
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}
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rgba[0] += int64(coeff) * int64(r)
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rgba[0] += int64(coeff) * int64(r)
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rgba[1] += int64(coeff) * int64(g)
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rgba[1] += int64(coeff) * int64(g)
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rgba[2] += int64(coeff) * int64(b)
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rgba[2] += int64(coeff) * int64(b)
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@ -112,10 +123,26 @@ func resizeRGBA(in *image.RGBA, out *image.NRGBA, scale float64, coeffs []int16,
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default:
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default:
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xi = 0
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xi = 0
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}
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}
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rgba[0] += int32(coeff) * int32(row[xi+0])
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rgba[1] += int32(coeff) * int32(row[xi+1])
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r := uint32(row[xi+0])
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rgba[2] += int32(coeff) * int32(row[xi+2])
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g := uint32(row[xi+1])
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rgba[3] += int32(coeff) * int32(row[xi+3])
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b := uint32(row[xi+2])
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a := uint32(row[xi+3])
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// reverse alpha-premultiplication.
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if a != 0 {
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r *= 0xffff
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r /= a
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g *= 0xffff
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g /= a
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b *= 0xffff
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b /= a
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}
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rgba[0] += int32(coeff) * int32(r)
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rgba[1] += int32(coeff) * int32(g)
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rgba[2] += int32(coeff) * int32(b)
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rgba[3] += int32(coeff) * int32(a)
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sum += int32(coeff)
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sum += int32(coeff)
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}
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}
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}
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}
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@ -192,10 +219,26 @@ func resizeRGBA64(in *image.RGBA64, out *image.NRGBA64, scale float64, coeffs []
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default:
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default:
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xi = 0
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xi = 0
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}
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}
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rgba[0] += int64(coeff) * int64(uint16(row[xi+0])<<8|uint16(row[xi+1]))
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rgba[1] += int64(coeff) * int64(uint16(row[xi+2])<<8|uint16(row[xi+3]))
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r := uint32(uint16(row[xi+0])<<8 | uint16(row[xi+1]))
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rgba[2] += int64(coeff) * int64(uint16(row[xi+4])<<8|uint16(row[xi+5]))
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g := uint32(uint16(row[xi+2])<<8 | uint16(row[xi+3]))
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rgba[3] += int64(coeff) * int64(uint16(row[xi+6])<<8|uint16(row[xi+7]))
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b := uint32(uint16(row[xi+4])<<8 | uint16(row[xi+5]))
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a := uint32(uint16(row[xi+6])<<8 | uint16(row[xi+7]))
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// reverse alpha-premultiplication.
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if a != 0 {
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r *= 0xffff
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r /= a
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g *= 0xffff
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g /= a
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b *= 0xffff
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b /= a
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}
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rgba[0] += int64(coeff) * int64(r)
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rgba[1] += int64(coeff) * int64(g)
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rgba[2] += int64(coeff) * int64(b)
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rgba[3] += int64(coeff) * int64(a)
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sum += int64(coeff)
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sum += int64(coeff)
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}
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}
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}
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}
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