op/paint: fix subimage rendering by ImageOp

This change is a follow-up to bcf3ff77ff, fixing the two renderers to
properly render images with non-zero origins.

Signed-off-by: Pierre Curto <pierre.curto@gmail.com>

gpu/compute.go

@@ -1802,8 +1802,9 @@ func (c *collector) collect(root *op.Ops, viewport image.Point, texOps *[]textur
 			paintState := state
 			if paintState.matType == materialTexture {
 				// Clip to the bounds of the image, to hide other images in the atlas.
-				bounds := paintState.image.src.Bounds()
-				c.addClip(&paintState, fview, layout.FRect(bounds), nil, ops.Key{}, 0, 0, false)
+				sz := state.image.src.Rect.Size()
+				bounds := f32.Rectangle{Max: layout.FPt(sz)}
+				c.addClip(&paintState, fview, bounds, nil, ops.Key{}, 0, 0, false)
 			}
 			intersect := paintState.clip.intersect
 			if intersect.Empty() {

gpu/gpu.go

@@ -955,7 +955,8 @@ loop:
 			inf := float32(1e6)
 			dst := f32.Rect(-inf, -inf, inf, inf)
 			if state.matType == materialTexture {
-				dst = layout.FRect(state.image.src.Rect)
+				sz := state.image.src.Rect.Size()
+				dst = f32.Rectangle{Max: layout.FPt(sz)}
 			}
 			clipData, bnd, partialTrans := d.boundsForTransformedRect(dst, t)
 			cl := viewport.Intersect(bnd.Add(off))

gpu/internal/rendertest/render_test.go

@@ -339,10 +339,10 @@ func TestImageRGBA(t *testing.T) {
 		w := newWindow(t, 10, 10)
 
 		im := image.NewRGBA(image.Rect(0, 0, 5, 5))
-		im.Set(3, 3, colornames.Black)
-		im.Set(4, 3, colornames.Black)
-		im.Set(3, 4, colornames.Black)
-		im.Set(4, 4, colornames.Black)
+		im.Set(3, 3, colornames.Red)
+		im.Set(4, 3, colornames.Red)
+		im.Set(3, 4, colornames.Red)
+		im.Set(4, 4, colornames.Red)
 		im = im.SubImage(image.Rect(2, 2, 5, 5)).(*image.RGBA)
 		paint.NewImageOp(im).Add(o)
 		paint.PaintOp{}.Add(o)
@@ -350,10 +350,10 @@ func TestImageRGBA(t *testing.T) {
 			t.Error(err)
 		}
 	}, func(r result) {
-		r.expect(1, 1, colornames.Black)
-		r.expect(2, 1, colornames.Black)
-		r.expect(1, 2, colornames.Black)
-		r.expect(2, 2, colornames.Black)
+		r.expect(1, 1, colornames.Red)
+		r.expect(2, 1, colornames.Red)
+		r.expect(1, 2, colornames.Red)
+		r.expect(2, 2, colornames.Red)
 	})
 }