aw/go-resize
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Separate color assignment and alpha pre-multiplication.

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This commit is contained in:
nfnt 2016-01-09 12:18:50 +01:00
parent 0f9f918da3
commit 4d93a29130
1 changed files with 25 additions and 11 deletions
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36
converter.go
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@ -158,13 +158,20 @@ func resizeNRGBA(in *image.NRGBA, out *image.RGBA, scale float64, coeffs []int16
xi = 0 xi = 0
} }
rgba[0] += int32(coeff) * int32(row[xi+0])
rgba[1] += int32(coeff) * int32(row[xi+1])
rgba[2] += int32(coeff) * int32(row[xi+2])
rgba[3] += int32(coeff) * int32(row[xi+3])
sum += int32(coeff)
// Forward alpha-premultiplication // Forward alpha-premultiplication
a := int32(row[xi+3]) a := int32(row[xi+3])
rgba[0] += int32(coeff) * int32(row[xi+0]) * a / 0xff rgba[0] *= a
rgba[1] += int32(coeff) * int32(row[xi+1]) * a / 0xff rgba[0] /= 0xff
rgba[2] += int32(coeff) * int32(row[xi+2]) * a / 0xff rgba[1] *= a
rgba[3] += int32(coeff) * a rgba[1] /= 0xff
sum += int32(coeff) rgba[2] *= a
rgba[2] /= 0xff
} }
} }
@ -252,13 +259,20 @@ func resizeNRGBA64(in *image.NRGBA64, out *image.RGBA64, scale float64, coeffs [
xi = 0 xi = 0
} }
// Forward alpha-premultiplication rgba[0] += int64(coeff) * int64(uint16(row[xi+0])<<8|uint16(row[xi+1]))
a := int64(row[xi+6])<<8 | int64(row[xi+7]) rgba[1] += int64(coeff) * int64(uint16(row[xi+2])<<8|uint16(row[xi+3]))
rgba[0] += int64(coeff) * (int64(row[xi+0])<<8 | int64(row[xi+1])) * a / 0xffff rgba[2] += int64(coeff) * int64(uint16(row[xi+4])<<8|uint16(row[xi+5]))
rgba[1] += int64(coeff) * (int64(row[xi+2])<<8 | int64(row[xi+3])) * a / 0xffff rgba[3] += int64(coeff) * int64(uint16(row[xi+6])<<8|uint16(row[xi+7]))
rgba[2] += int64(coeff) * (int64(row[xi+4])<<8 | int64(row[xi+5])) * a / 0xffff
rgba[3] += int64(coeff) * a
sum += int64(coeff) sum += int64(coeff)
// Forward alpha-premultiplication
a := int64(uint16(row[xi+6])<<8 | uint16(row[xi+7]))
rgba[0] *= a
rgba[0] /= 0xffff
rgba[1] *= a
rgba[1] /= 0xffff
rgba[2] *= a
rgba[2] /= 0xffff
} }
} }