diff options
| -rw-r--r-- | src/types/color.nim | 25 |
1 files changed, 11 insertions, 14 deletions
diff --git a/src/types/color.nim b/src/types/color.nim index d917569a..70908508 100644 --- a/src/types/color.nim +++ b/src/types/color.nim @@ -1,4 +1,3 @@ -import math import options import strutils import tables @@ -295,19 +294,17 @@ func rgba*(r, g, b, a: uint8): RGBAColor func premul(c: RGBAColor): RGBAColor = return RGBAColor(fastmul(c, uint32(c.a))) -const straightAlphaTable = (func(): auto = - var table: array[256, array[256, uint8]] - for a in 0 ..< 256: - let multiplier = if a > 0: (255 / a.float32) else: 0 - for c in 0 ..< 256: - table[a][c] = min(round((c.float32 * multiplier)), 255).uint8 - return table)() - -proc straight*(c: RGBAColor): RGBAColor = - let r = straightAlphaTable[c.a][c.r] - let g = straightAlphaTable[c.a][c.g] - let b = straightAlphaTable[c.a][c.b] - return rgba(r, g, b, c.a) +# This is somewhat faster than floats or a lookup table, and is correct for +# all inputs. +proc straight(c: RGBAColor): RGBAColor = + let a8 = c.a + if a8 == 0: + return RGBAColor(0) + let a = uint32(a8) + let r = (uint32(c.r) * 0xFF00 div a + 0x80) shr 8 + let g = (uint32(c.g) * 0xFF00 div a + 0x80) shr 8 + let b = (uint32(c.b) * 0xFF00 div a + 0x80) shr 8 + return RGBAColor((a shl 24) or (r shl 16) or (g shl 8) or b) func blend*(c0, c1: RGBAColor): RGBAColor = let pc0 = c0.premul() |