diff options
Diffstat (limited to 'src/pkg/image/color/color.go')
| -rw-r--r-- | src/pkg/image/color/color.go | 26 |
1 files changed, 10 insertions, 16 deletions
diff --git a/src/pkg/image/color/color.go b/src/pkg/image/color/color.go index 29a7b8a40..ff596a76a 100644 --- a/src/pkg/image/color/color.go +++ b/src/pkg/image/color/color.go @@ -253,13 +253,6 @@ func gray16Model(c Color) Color { // Palette is a palette of colors. type Palette []Color -func diff(a, b uint32) uint32 { - if a > b { - return a - b - } - return b - a -} - // Convert returns the palette color closest to c in Euclidean R,G,B space. func (p Palette) Convert(c Color) Color { if len(p) == 0 { @@ -271,19 +264,20 @@ func (p Palette) Convert(c Color) Color { // Index returns the index of the palette color closest to c in Euclidean // R,G,B space. func (p Palette) Index(c Color) int { + // A batch version of this computation is in image/draw/draw.go. + cr, cg, cb, _ := c.RGBA() - // Shift by 1 bit to avoid potential uint32 overflow in sum-squared-difference. - cr >>= 1 - cg >>= 1 - cb >>= 1 ret, bestSSD := 0, uint32(1<<32-1) for i, v := range p { vr, vg, vb, _ := v.RGBA() - vr >>= 1 - vg >>= 1 - vb >>= 1 - dr, dg, db := diff(cr, vr), diff(cg, vg), diff(cb, vb) - ssd := (dr * dr) + (dg * dg) + (db * db) + // We shift by 1 bit to avoid potential uint32 overflow in + // sum-squared-difference. + delta := (int32(cr) - int32(vr)) >> 1 + ssd := uint32(delta * delta) + delta = (int32(cg) - int32(vg)) >> 1 + ssd += uint32(delta * delta) + delta = (int32(cb) - int32(vb)) >> 1 + ssd += uint32(delta * delta) if ssd < bestSSD { if ssd == 0 { return i |