op/paint: remove unnecessary check in ImageOp

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

gpu/internal/driver/driver.go

@@ -229,8 +229,9 @@ func flipImageY(stride, height int, pixels []byte) {
 func UploadImage(t Texture, offset image.Point, img *image.RGBA) {
 	var pixels []byte
 	size := img.Bounds().Size()
-	start := img.PixOffset(0, 0)
-	end := img.PixOffset(size.X, size.Y-1)
+	min := img.Rect.Min
+	start := img.PixOffset(min.X, min.Y)
+	end := img.PixOffset(min.X+size.X, min.Y+size.Y-1)
 	pixels = img.Pix[start:end]
 	t.Upload(offset, size, pixels, img.Stride)
 }

gpu/internal/rendertest/render_test.go

@@ -334,6 +334,29 @@ func TestZeroImage(t *testing.T) {
 	}
 }
 
+func TestImageRGBA(t *testing.T) {
+	run(t, func(o *op.Ops) {
+		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 = im.SubImage(image.Rect(2, 2, 5, 5)).(*image.RGBA)
+		paint.NewImageOp(im).Add(o)
+		paint.PaintOp{}.Add(o)
+		if err := w.Frame(o); err != nil {
+			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)
+	})
+}
+
 // lerp calculates linear interpolation with color b and p.
 func lerp(a, b f32color.RGBA, p float32) f32color.RGBA {
 	return f32color.RGBA{

gpu/internal/rendertest/util_test.go

@@ -145,6 +145,10 @@ func verifyRef(t *testing.T, img *image.RGBA, frame int) (ok bool) {
 	if frame != 0 {
 		path = filepath.Join("refs", t.Name()+"_"+strconv.Itoa(frame)+".png")
 	}
+	if *dumpImages {
+		saveImage(t, path, img)
+		return true
+	}
 	b, err := ioutil.ReadFile(path)
 	if err != nil {
 		t.Error("could not open ref:", err)