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image: tighten Paletted.Opaque to check only those palette entries

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in the image, not all palette entries.

R=r
CC=golang-dev
https://golang.org/cl/4672049
This commit is contained in:
Nigel Tao 2011-07-07 16:32:19 +10:00
parent 07c9a92564
commit 03f987c8ea
2 changed files with 20 additions and 2 deletions
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17
src/pkg/image/image.go
View File

@ -548,7 +548,7 @@ func NewGray16(w, h int) *Gray16 {
return &Gray16{pix, w, Rectangle{ZP, Point{w, h}}}
}
// A PalettedColorModel represents a fixed palette of colors.
// A PalettedColorModel represents a fixed palette of at most 256 colors.
type PalettedColorModel []Color
func diff(a, b uint32) uint32 {
@ -648,7 +648,20 @@ func (p *Paletted) SubImage(r Rectangle) Image {
// Opaque scans the entire image and returns whether or not it is fully opaque.
func (p *Paletted) Opaque() bool {
for _, c := range p.Palette {
var present [256]bool
base := p.Rect.Min.Y * p.Stride
i0, i1 := base+p.Rect.Min.X, base+p.Rect.Max.X
for y := p.Rect.Min.Y; y < p.Rect.Max.Y; y++ {
for _, c := range p.Pix[i0:i1] {
present[c] = true
}
i0 += p.Stride
i1 += p.Stride
}
for i, c := range p.Palette {
if !present[i] {
continue
}
_, _, _, a := c.RGBA()
if a != 0xffff {
return false

5
src/pkg/image/image_test.go
View File

@ -10,6 +10,7 @@ import (
type image interface {
Image
Opaque() bool
Set(int, int, Color)
SubImage(Rectangle) Image
}
@ -49,6 +50,10 @@ func TestImage(t *testing.T) {
t.Errorf("%T: at (6, 3), want a non-zero color, got %v", m, m.At(6, 3))
continue
}
if !m.SubImage(Rect(6, 3, 7, 4)).(image).Opaque() {
t.Errorf("%T: at (6, 3) was not opaque", m)
continue
}
m = m.SubImage(Rect(3, 2, 9, 8)).(image)
if !Rect(3, 2, 9, 8).Eq(m.Bounds()) {
t.Errorf("%T: sub-image want bounds %v, got %v", m, Rect(3, 2, 9, 8), m.Bounds())