Fixes #836.

R=gri
CC=golang-dev
https://golang.org/cl/1548042

diff --git a/src/pkg/exp/draw/draw.go b/src/pkg/exp/draw/draw.go
index 7d9b43ade8d7749e5a682ec2d85cfadb05511ba6..6c50faa84cb032bcb36712b681e6714e6d8c7772 100644 (file)
--- a/src/pkg/exp/draw/draw.go
+++ b/src/pkg/exp/draw/draw.go
@@ -182,7 +182,7 @@ func drawCopyOver(dst *image.RGBA, r Rectangle, src *image.RGBA, sp Point) {
        y0, y1 := r.Min.Y, r.Max.Y
        for y, sy := y0, sp.Y; y != y1; y, sy = y+1, sy+1 {
                dpix := dst.Pixel[y]
-               spix := src.Pixel[y]
+               spix := src.Pixel[sy]
                for x, sx := x0, sp.X; x != x1; x, sx = x+1, sx+1 {
                        // For unknown reasons, even though both dpix[x] and spix[sx] are
                        // image.RGBAColors, on an x86 CPU it seems fastest to call RGBA

diff --git a/src/pkg/exp/draw/draw_test.go b/src/pkg/exp/draw/draw_test.go
index 5303f2b3d85f056421bb9282d12945e35f746c1f..e9fde2535765a98686dddab9e9184ff901c4fed9 100644 (file)
--- a/src/pkg/exp/draw/draw_test.go
+++ b/src/pkg/exp/draw/draw_test.go
@@ -149,3 +149,17 @@ loop:
                }
        }
 }
+
+// TestIssue836 verifies http://code.google.com/p/go/issues/detail?id=836.
+func TestIssue836(t *testing.T) {
+       a := image.NewRGBA(1, 1)
+       b := image.NewRGBA(2, 2)
+       b.Set(0, 0, image.RGBAColor{0, 0, 0, 5})
+       b.Set(1, 0, image.RGBAColor{0, 0, 5, 5})
+       b.Set(0, 1, image.RGBAColor{0, 5, 0, 5})
+       b.Set(1, 1, image.RGBAColor{5, 0, 0, 5})
+       Draw(a, Rect(0, 0, 1, 1), b, Pt(1, 1))
+       if !eq(image.RGBAColor{5, 0, 0, 5}, a.At(0, 0)) {
+               t.Errorf("Issue 836: want %v got %v", image.RGBAColor{5, 0, 0, 5}, a.At(0, 0))
+       }
+}