internal/graphicscommand: bug fix: replacePixelsCommand should not read pixels

Reading pixels, writing pixels, and using the image as a source might cause a flaky behavior with Metal. Stop reading pixels if possible. Closes #2180
2024-12-25 11:18:54 +01:00 · 2022-07-05 13:26:45 +09:00 · 2022-07-05 13:26:45 +09:00 · 8522bfd0bf
commit 8522bfd0bf
parent dd805c9414
13 changed files with 195 additions and 477 deletions
--- a/internal/atlas/image.go
+++ b/internal/atlas/image.go
@ -495,17 +495,21 @@ func (i *Image) drawTriangles(srcs [graphics.ShaderImageNum]*Image, vertices []f
 }

 // ReplacePixels replaces the pixels on the image.
-func (i *Image) ReplacePixels(pix []byte, mask []byte) {
+func (i *Image) ReplacePixels(pix []byte, x, y, width, height int) {
 	backendsM.Lock()
 	defer backendsM.Unlock()
-	i.replacePixels(pix, mask)
+	i.replacePixels(pix, x, y, width, height)
 }

-func (i *Image) replacePixels(pix []byte, mask []byte) {
+func (i *Image) replacePixels(pix []byte, x, y, width, height int) {
 	if i.disposed {
 		panic("atlas: the image must not be disposed at replacePixels")
 	}

+	if l := 4 * width * height; len(pix) != l {
+		panic(fmt.Sprintf("atlas: len(p) must be %d but %d", l, len(pix)))
+	}
+
 	i.resetUsedAsSourceCount()

 	if i.backend == nil {
@ -516,29 +520,20 @@ func (i *Image) replacePixels(pix []byte, mask []byte) {
 	}

 	px, py, pw, ph := i.regionWithPadding()
-	if pix == nil {
-		if mask != nil {
-			panic("atlas: mask must be nil when pix is nil")
+
+	if x != 0 || y != 0 || width != i.width || height != i.height || i.paddingSize() == 0 {
+		x += px + i.paddingSize()
+		y += py + i.paddingSize()
+
+		if pix == nil {
+			i.backend.restorable.ReplacePixels(nil, x, y, width, height)
+			return
 		}
-		i.backend.restorable.ReplacePixels(nil, nil, px, py, pw, ph)
-		return
-	}

-	ow, oh := pw-2*i.paddingSize(), ph-2*i.paddingSize()
-	if l := 4 * ow * oh; len(pix) != l {
-		panic(fmt.Sprintf("atlas: len(p) must be %d but %d", l, len(pix)))
-	}
-
-	if i.paddingSize() == 0 {
 		// Copy pixels in the case when pix is modified before the graphics command is executed.
-		pix2 := make([]byte, len(pix))
+		pix2 := theTemporaryBytes.alloc(len(pix))
 		copy(pix2, pix)
-		var mask2 []byte
-		if mask != nil {
-			mask2 = make([]byte, len(mask))
-			copy(mask2, mask)
-		}
-		i.backend.restorable.ReplacePixels(pix2, mask2, px, py, pw, ph)
+		i.backend.restorable.ReplacePixels(pix2, x, y, width, height)
 		return
 	}

@ -546,6 +541,7 @@ func (i *Image) replacePixels(pix []byte, mask []byte) {

 	// Clear the edges. pixb might not be zero-cleared.
 	// TODO: These loops assume that paddingSize is 1.
+	// TODO: Is clearing edges explicitly really needed?
 	const paddingSize = 1
 	if paddingSize != i.paddingSize() {
 		panic(fmt.Sprintf("atlas: replacePixels assumes the padding is always 1 but the actual padding was %d", i.paddingSize()))
@ -567,45 +563,13 @@ func (i *Image) replacePixels(pix []byte, mask []byte) {
 	}

 	// Copy the content.
-	for j := 0; j < oh; j++ {
-		copy(pixb[4*((j+paddingSize)*pw+paddingSize):], pix[4*j*ow:4*(j+1)*ow])
+	for j := 0; j < height; j++ {
+		copy(pixb[4*((j+paddingSize)*pw+paddingSize):], pix[4*j*width:4*(j+1)*width])
 	}

-	// Add the paddings to the mask if needed.
-	if mask != nil {
-		origMask := mask
-		mask = theTemporaryBytes.alloc((pw*ph-1)/8 + 1)
-		// Clear the allocated region explicitly (#2089).
-		for i := range mask {
-			mask[i] = 0
-		}
-		for i := 0; i < pw; i++ {
-			// Top edge
-			idx := i
-			mask[idx/8] |= 1 << (idx % 8)
-			// Bottom edge
-			idx = (ph-1)*pw + i
-			mask[idx/8] |= 1 << (idx % 8)
-		}
-		for j := 1; j < ph-1; j++ {
-			// Left edge
-			idx := j * pw
-			mask[idx/8] |= 1 << (idx % 8)
-			// Right edge
-			idx = j*pw + pw - 1
-			mask[idx/8] |= 1 << (idx % 8)
-
-			// Content
-			for i := 1; i < pw-1; i++ {
-				idx := j*pw + i
-				origIdx := (j-paddingSize)*(pw-paddingSize*2) + i - paddingSize
-				origValue := (origMask[origIdx/8] >> (origIdx % 8)) & 1
-				mask[idx/8] |= origValue << (idx % 8)
-			}
-		}
-	}
-
-	i.backend.restorable.ReplacePixels(pixb, mask, px, py, pw, ph)
+	x += px
+	y += py
+	i.backend.restorable.ReplacePixels(pixb, x, y, pw, ph)
 }

 func (img *Image) Pixels(graphicsDriver graphicsdriver.Graphics) ([]byte, error) {
--- a/internal/atlas/image_test.go
+++ b/internal/atlas/image_test.go
@ -63,17 +63,17 @@ func TestEnsureIsolated(t *testing.T) {
 	img1 := atlas.NewImage(bigSize, 100, atlas.ImageTypeRegular)
 	defer img1.MarkDisposed()
 	// Ensure img1's region is allocated.
-	img1.ReplacePixels(make([]byte, 4*bigSize*100), nil)
+	img1.ReplacePixels(make([]byte, 4*bigSize*100), 0, 0, bigSize, 100)

 	img2 := atlas.NewImage(100, bigSize, atlas.ImageTypeRegular)
 	defer img2.MarkDisposed()
-	img2.ReplacePixels(make([]byte, 4*100*bigSize), nil)
+	img2.ReplacePixels(make([]byte, 4*100*bigSize), 0, 0, 100, bigSize)

 	const size = 32

 	img3 := atlas.NewImage(size/2, size/2, atlas.ImageTypeRegular)
 	defer img3.MarkDisposed()
-	img3.ReplacePixels(make([]byte, (size/2)*(size/2)*4), nil)
+	img3.ReplacePixels(make([]byte, (size/2)*(size/2)*4), 0, 0, size/2, size/2)

 	img4 := atlas.NewImage(size, size, atlas.ImageTypeRegular)
 	defer img4.MarkDisposed()
@ -90,7 +90,7 @@ func TestEnsureIsolated(t *testing.T) {
 			pix[4*(i+j*size)+3] = byte(i + j)
 		}
 	}
-	img4.ReplacePixels(pix, nil)
+	img4.ReplacePixels(pix, 0, 0, size, size)

 	const (
 		dx0 = size / 4
@ -157,11 +157,11 @@ func TestReputOnAtlas(t *testing.T) {

 	img0 := atlas.NewImage(size, size, atlas.ImageTypeRegular)
 	defer img0.MarkDisposed()
-	img0.ReplacePixels(make([]byte, 4*size*size), nil)
+	img0.ReplacePixels(make([]byte, 4*size*size), 0, 0, size, size)

 	img1 := atlas.NewImage(size, size, atlas.ImageTypeRegular)
 	defer img1.MarkDisposed()
-	img1.ReplacePixels(make([]byte, 4*size*size), nil)
+	img1.ReplacePixels(make([]byte, 4*size*size), 0, 0, size, size)
 	if got, want := img1.IsOnAtlasForTesting(), true; got != want {
 		t.Errorf("got: %v, want: %v", got, want)
 	}
@ -177,12 +177,12 @@ func TestReputOnAtlas(t *testing.T) {
 			pix[4*(i+j*size)+3] = byte(i + j)
 		}
 	}
-	img2.ReplacePixels(pix, nil)
+	img2.ReplacePixels(pix, 0, 0, size, size)

 	// Create a volatile image. This should always be isolated.
 	img3 := atlas.NewImage(size, size, atlas.ImageTypeVolatile)
 	defer img3.MarkDisposed()
-	img1.ReplacePixels(make([]byte, 4*size*size), nil)
+	img1.ReplacePixels(make([]byte, 4*size*size), 0, 0, size, size)
 	if got, want := img3.IsOnAtlasForTesting(), false; got != want {
 		t.Errorf("got: %v, want: %v", got, want)
 	}
@ -271,7 +271,7 @@ func TestReputOnAtlas(t *testing.T) {
 		if err := atlas.PutImagesOnAtlasForTesting(ui.GraphicsDriverForTesting()); err != nil {
 			t.Fatal(err)
 		}
-		img1.ReplacePixels(make([]byte, 4*size*size), nil)
+		img1.ReplacePixels(make([]byte, 4*size*size), 0, 0, size, size)
 		img0.DrawTriangles([graphics.ShaderImageNum]*atlas.Image{img1}, vs, is, affine.ColorMIdentity{}, graphicsdriver.CompositeModeCopy, graphicsdriver.FilterNearest, graphicsdriver.AddressUnsafe, dr, graphicsdriver.Region{}, [graphics.ShaderImageNum - 1][2]float32{}, nil, nil, false)
 		if got, want := img1.IsOnAtlasForTesting(), false; got != want {
 			t.Errorf("got: %v, want: %v", got, want)
@ -313,7 +313,7 @@ func TestExtend(t *testing.T) {
 		p0[4*i+2] = byte(i)
 		p0[4*i+3] = byte(i)
 	}
-	img0.ReplacePixels(p0, nil)
+	img0.ReplacePixels(p0, 0, 0, w0, h0)

 	const w1, h1 = minImageSizeForTesting + 1, 100
 	img1 := atlas.NewImage(w1, h1, atlas.ImageTypeRegular)
@ -327,7 +327,7 @@ func TestExtend(t *testing.T) {
 		p1[4*i+3] = byte(i)
 	}
 	// Ensure to allocate
-	img1.ReplacePixels(p1, nil)
+	img1.ReplacePixels(p1, 0, 0, w1, h1)

 	pix0, err := img0.Pixels(ui.GraphicsDriverForTesting())
 	if err != nil {
@ -382,7 +382,7 @@ func TestReplacePixelsAfterDrawTriangles(t *testing.T) {
 		pix[4*i+2] = byte(i)
 		pix[4*i+3] = byte(i)
 	}
-	src.ReplacePixels(pix, nil)
+	src.ReplacePixels(pix, 0, 0, w, h)

 	vs := quadVertices(w, h, 0, 0, 1)
 	is := graphics.QuadIndices()
@ -393,7 +393,7 @@ func TestReplacePixelsAfterDrawTriangles(t *testing.T) {
 		Height: h,
 	}
 	dst.DrawTriangles([graphics.ShaderImageNum]*atlas.Image{src}, vs, is, affine.ColorMIdentity{}, graphicsdriver.CompositeModeCopy, graphicsdriver.FilterNearest, graphicsdriver.AddressUnsafe, dr, graphicsdriver.Region{}, [graphics.ShaderImageNum - 1][2]float32{}, nil, nil, false)
-	dst.ReplacePixels(pix, nil)
+	dst.ReplacePixels(pix, 0, 0, w, h)

 	pix, err := dst.Pixels(ui.GraphicsDriverForTesting())
 	if err != nil {
@ -430,7 +430,7 @@ func TestSmallImages(t *testing.T) {
 		pix[4*i+2] = 0xff
 		pix[4*i+3] = 0xff
 	}
-	src.ReplacePixels(pix, nil)
+	src.ReplacePixels(pix, 0, 0, w, h)

 	vs := quadVertices(w, h, 0, 0, 1)
 	is := graphics.QuadIndices()
@ -477,7 +477,7 @@ func TestLongImages(t *testing.T) {
 		pix[4*i+2] = 0xff
 		pix[4*i+3] = 0xff
 	}
-	src.ReplacePixels(pix, nil)
+	src.ReplacePixels(pix, 0, 0, w, h)

 	const scale = 120
 	vs := quadVertices(w, h, 0, 0, scale)
@ -527,12 +527,12 @@ func TestExtendWithBigImage(t *testing.T) {
 	img0 := atlas.NewImage(1, 1, atlas.ImageTypeRegular)
 	defer img0.MarkDisposed()

-	img0.ReplacePixels(make([]byte, 4*1*1), nil)
+	img0.ReplacePixels(make([]byte, 4*1*1), 0, 0, 1, 1)

 	img1 := atlas.NewImage(minImageSizeForTesting+1, minImageSizeForTesting+1, atlas.ImageTypeRegular)
 	defer img1.MarkDisposed()

-	img1.ReplacePixels(make([]byte, 4*(minImageSizeForTesting+1)*(minImageSizeForTesting+1)), nil)
+	img1.ReplacePixels(make([]byte, 4*(minImageSizeForTesting+1)*(minImageSizeForTesting+1)), 0, 0, minImageSizeForTesting+1, minImageSizeForTesting+1)
 }

 // Issue #1217
@ -545,7 +545,7 @@ func TestMaxImageSize(t *testing.T) {
 	s := maxImageSizeForTesting - 2*paddingSize
 	img1 := atlas.NewImage(s, s, atlas.ImageTypeRegular)
 	defer img1.MarkDisposed()
-	img1.ReplacePixels(make([]byte, 4*s*s), nil)
+	img1.ReplacePixels(make([]byte, 4*s*s), 0, 0, s, s)
 }

 // Issue #1217 (disabled)
@ -558,7 +558,7 @@ func Disable_TestMinImageSize(t *testing.T) {
 	s := minImageSizeForTesting
 	img := atlas.NewImage(s, s, atlas.ImageTypeRegular)
 	defer img.MarkDisposed()
-	img.ReplacePixels(make([]byte, 4*s*s), nil)
+	img.ReplacePixels(make([]byte, 4*s*s), 0, 0, s, s)
 }

 func TestMaxImageSizeJust(t *testing.T) {
@ -567,7 +567,7 @@ func TestMaxImageSizeJust(t *testing.T) {
 	// TODO: Should we allow such this size for ImageTypeRegular?
 	img := atlas.NewImage(s, s, atlas.ImageTypeUnmanaged)
 	defer img.MarkDisposed()
-	img.ReplacePixels(make([]byte, 4*s*s), nil)
+	img.ReplacePixels(make([]byte, 4*s*s), 0, 0, s, s)
 }

 func TestMaxImageSizeExceeded(t *testing.T) {
@ -582,7 +582,7 @@ func TestMaxImageSizeExceeded(t *testing.T) {
 		}
 	}()

-	img.ReplacePixels(make([]byte, 4*(s+1)*s), nil)
+	img.ReplacePixels(make([]byte, 4*(s+1)*s), 0, 0, s+1, s)
 }

 // Issue #1421
@ -704,7 +704,7 @@ func TestImageReplacePixelsModify(t *testing.T) {
 				pix[4*(i+j*size)+3] = byte(i + j)
 			}
 		}
-		img.ReplacePixels(pix, nil)
+		img.ReplacePixels(pix, 0, 0, size, size)

 		// Modify pix after ReplacePixels.
 		for j := 0; j < size; j++ {
--- a/internal/atlas/shader_test.go
+++ b/internal/atlas/shader_test.go
@ -62,9 +62,9 @@ func TestImageDrawTwice(t *testing.T) {

 	dst := atlas.NewImage(w, h, atlas.ImageTypeRegular)
 	src0 := atlas.NewImage(w, h, atlas.ImageTypeRegular)
-	src0.ReplacePixels([]byte{0xff, 0xff, 0xff, 0xff}, nil)
+	src0.ReplacePixels([]byte{0xff, 0xff, 0xff, 0xff}, 0, 0, w, h)
 	src1 := atlas.NewImage(w, h, atlas.ImageTypeRegular)
-	src1.ReplacePixels([]byte{0x80, 0x80, 0x80, 0xff}, nil)
+	src1.ReplacePixels([]byte{0x80, 0x80, 0x80, 0xff}, 0, 0, w, h)

 	vs := quadVertices(w, h, 0, 0, 1)
 	is := graphics.QuadIndices()
--- a/internal/buffered/image.go
+++ b/internal/buffered/image.go
@ -29,9 +29,7 @@ type Image struct {
 	width  int
 	height int

-	pixels               []byte
-	mask                 []byte
-	needsToResolvePixels bool
+	pixels []byte
 }

 func BeginFrame(graphicsDriver graphicsdriver.Graphics) error {
@ -68,21 +66,6 @@ func (i *Image) initialize(imageType atlas.ImageType) {

 func (i *Image) invalidatePixels() {
 	i.pixels = nil
-	i.mask = nil
-	i.needsToResolvePixels = false
-}
-
-func (i *Image) resolvePendingPixels(keepPendingPixels bool) {
-	if !i.needsToResolvePixels {
-		return
-	}
-
-	i.img.ReplacePixels(i.pixels, i.mask)
-	if !keepPendingPixels {
-		i.pixels = nil
-		i.mask = nil
-	}
-	i.needsToResolvePixels = false
 }

 func (i *Image) MarkDisposed() {
@ -102,14 +85,7 @@ func (img *Image) At(graphicsDriver graphicsdriver.Graphics, x, y int) (r, g, b,

 	idx := (y*img.width + x)
 	if img.pixels != nil {
-		if img.mask == nil {
-			return img.pixels[4*idx], img.pixels[4*idx+1], img.pixels[4*idx+2], img.pixels[4*idx+3], nil
-		}
-		if img.mask[idx/8]<<(idx%8)&1 != 0 {
-			return img.pixels[4*idx], img.pixels[4*idx+1], img.pixels[4*idx+2], img.pixels[4*idx+3], nil
-		}
-
-		img.resolvePendingPixels(false)
+		return img.pixels[4*idx], img.pixels[4*idx+1], img.pixels[4*idx+2], img.pixels[4*idx+3], nil
 	}

 	pix, err := img.img.Pixels(graphicsDriver)
@ -117,8 +93,6 @@ func (img *Image) At(graphicsDriver graphicsdriver.Graphics, x, y int) (r, g, b,
 		return 0, 0, 0, 0, err
 	}
 	img.pixels = pix
-	// When pixels represents the whole pixels, the mask is not needed.
-	img.mask = nil
 	return img.pixels[4*idx], img.pixels[4*idx+1], img.pixels[4*idx+2], img.pixels[4*idx+3], nil
 }

@ -143,40 +117,8 @@ func (i *Image) ReplacePixels(pix []byte, x, y, width, height int) {
 		}
 	}

-	if x == 0 && y == 0 && width == i.width && height == i.height {
-		i.invalidatePixels()
-		i.img.ReplacePixels(pix, nil)
-		return
-	}
-
-	// TODO: If width/height is big enough, ReplacePixels can be called instead of replacePendingPixels.
-	// Check if this is efficient.
-
-	i.replacePendingPixels(pix, x, y, width, height)
-}
-
-func (img *Image) replacePendingPixels(pix []byte, x, y, width, height int) {
-	if img.pixels == nil {
-		img.pixels = make([]byte, 4*img.width*img.height)
-		if img.mask == nil {
-			img.mask = make([]byte, (img.width*img.height-1)/8+1)
-		}
-	}
-	for j := 0; j < height; j++ {
-		copy(img.pixels[4*((j+y)*img.width+x):], pix[4*j*width:4*(j+1)*width])
-	}
-
-	// A mask is created only when partial regions are replaced by replacePendingPixels.
-	if img.mask != nil {
-		for j := 0; j < height; j++ {
-			for i := 0; i < width; i++ {
-				idx := (y+j)*img.width + x + i
-				img.mask[idx/8] |= 1 << (idx % 8)
-			}
-		}
-	}
-
-	img.needsToResolvePixels = true
+	i.invalidatePixels()
+	i.img.ReplacePixels(pix, x, y, width, height)
 }

 // DrawTriangles draws the src image with the given vertices.
@ -203,22 +145,19 @@ func (i *Image) DrawTriangles(srcs [graphics.ShaderImageNum]*Image, vertices []f
 	if shader == nil {
 		// Fast path for rendering without a shader (#1355).
 		img := srcs[0]
-		img.resolvePendingPixels(true)
 		imgs[0] = img.img
 	} else {
 		for i, img := range srcs {
 			if img == nil {
 				continue
 			}
-			img.resolvePendingPixels(true)
 			imgs[i] = img.img
 		}
 		s = shader.shader
 	}
-	i.resolvePendingPixels(false)

-	i.img.DrawTriangles(imgs, vertices, indices, colorm, mode, filter, address, dstRegion, srcRegion, subimageOffsets, s, uniforms, evenOdd)
 	i.invalidatePixels()
+	i.img.DrawTriangles(imgs, vertices, indices, colorm, mode, filter, address, dstRegion, srcRegion, subimageOffsets, s, uniforms, evenOdd)
 }

 type Shader struct {
--- a/internal/graphicscommand/command.go
+++ b/internal/graphicscommand/command.go
@ -523,37 +523,11 @@ func (c *replacePixelsCommand) String() string {

 // Exec executes the replacePixelsCommand.
 func (c *replacePixelsCommand) Exec(graphicsDriver graphicsdriver.Graphics, indexOffset int) error {
-	var lastArgIdx int
-	for i, a := range c.args {
-		if a.Mask == nil {
-			continue
-		}
-		if len(c.args[lastArgIdx:i]) > 0 {
-			c.dst.image.ReplacePixels(c.args[lastArgIdx:i])
-			lastArgIdx = i
-		}
-
-		orig := make([]byte, 4*c.dst.width*c.dst.height)
-		if err := c.dst.image.ReadPixels(orig); err != nil {
-			return err
-		}
-		for j := 0; j < a.Height; j++ {
-			for i := 0; i < a.Width; i++ {
-				idx := j*a.Width + i
-				if a.Mask[idx/8]>>(idx%8)&1 == 0 {
-					srcIdx := (a.Y+j)*c.dst.width + a.X + i
-					copy(a.Pixels[4*idx:4*(idx+1)], orig[4*srcIdx:4*(srcIdx+1)])
-				}
-			}
-		}
-
-		a.Mask = nil
+	if len(c.args) == 0 {
+		return nil
 	}
-
-	if len(c.args[lastArgIdx:]) > 0 {
-		if err := c.dst.image.ReplacePixels(c.args[lastArgIdx:]); err != nil {
-			return err
-		}
+	if err := c.dst.image.ReplacePixels(c.args); err != nil {
+		return err
 	}
 	return nil
 }
--- a/internal/graphicscommand/image.go
+++ b/internal/graphicscommand/image.go
@ -166,10 +166,9 @@ func (i *Image) ReadPixels(graphicsDriver graphicsdriver.Graphics, buf []byte) e
 	return nil
 }

-func (i *Image) ReplacePixels(pixels []byte, mask []byte, x, y, width, height int) {
+func (i *Image) ReplacePixels(pixels []byte, x, y, width, height int) {
 	i.bufferedRP = append(i.bufferedRP, &graphicsdriver.ReplacePixelsArgs{
 		Pixels: pixels,
-		Mask:   mask,
 		X:      x,
 		Y:      y,
 		Width:  width,
--- a/internal/graphicscommand/image_test.go
+++ b/internal/graphicscommand/image_test.go
@ -87,60 +87,11 @@ func TestReplacePixelsPartAfterDrawTriangles(t *testing.T) {
 	}
 	dst.DrawTriangles([graphics.ShaderImageNum]*graphicscommand.Image{clr}, [graphics.ShaderImageNum - 1][2]float32{}, vs, is, affine.ColorMIdentity{}, graphicsdriver.CompositeModeClear, graphicsdriver.FilterNearest, graphicsdriver.AddressUnsafe, dr, graphicsdriver.Region{}, nil, nil, false)
 	dst.DrawTriangles([graphics.ShaderImageNum]*graphicscommand.Image{src}, [graphics.ShaderImageNum - 1][2]float32{}, vs, is, affine.ColorMIdentity{}, graphicsdriver.CompositeModeSourceOver, graphicsdriver.FilterNearest, graphicsdriver.AddressUnsafe, dr, graphicsdriver.Region{}, nil, nil, false)
-	dst.ReplacePixels(make([]byte, 4), nil, 0, 0, 1, 1)
+	dst.ReplacePixels(make([]byte, 4), 0, 0, 1, 1)

 	// TODO: Check the result.
 }

-func TestReplacePixelsWithMask(t *testing.T) {
-	const w, h = 4, 3
-	src := graphicscommand.NewImage(w, h, false)
-	dst := graphicscommand.NewImage(w, h, false)
-
-	vs := quadVertices(src, w, h)
-	is := graphics.QuadIndices()
-	dr := graphicsdriver.Region{
-		X:      0,
-		Y:      0,
-		Width:  w,
-		Height: h,
-	}
-	dst.DrawTriangles([graphics.ShaderImageNum]*graphicscommand.Image{src}, [graphics.ShaderImageNum - 1][2]float32{}, vs, is, affine.ColorMIdentity{}, graphicsdriver.CompositeModeClear, graphicsdriver.FilterNearest, graphicsdriver.AddressUnsafe, dr, graphicsdriver.Region{}, nil, nil, false)
-
-	pix0 := make([]byte, 4*w*h)
-	for i := range pix0 {
-		pix0[i] = 0x40
-	}
-	dst.ReplacePixels(pix0, nil, 0, 0, w, h)
-
-	pix1 := make([]byte, 4*w*h)
-	for i := range pix1 {
-		pix1[i] = 0x80
-	}
-	mask1 := []byte{0b11110110, 0b00000110}
-	dst.ReplacePixels(pix1, mask1, 0, 0, w, h)
-
-	readPix := make([]byte, 4*w*h)
-	if err := dst.ReadPixels(ui.GraphicsDriverForTesting(), readPix); err != nil {
-		t.Fatal(err)
-	}
-	for j := 0; j < h; j++ {
-		for i := 0; i < w; i++ {
-			idx := 4 * (i + w*j)
-			got := color.RGBA{readPix[idx], readPix[idx+1], readPix[idx+2], readPix[idx+3]}
-			var want color.RGBA
-			if (i != 0 && i != w-1) || (j != 0 && j != h-1) {
-				want = color.RGBA{0x80, 0x80, 0x80, 0x80}
-			} else {
-				want = color.RGBA{0x40, 0x40, 0x40, 0x40}
-			}
-			if got != want {
-				t.Errorf("dst.At(%d, %d) after ReplacePixels: got %v, want: %v", i, j, got, want)
-			}
-		}
-	}
-}
-
 func TestShader(t *testing.T) {
 	const w, h = 16, 16
 	clr := graphicscommand.NewImage(w, h, false)
--- a/internal/graphicsdriver/graphics.go
+++ b/internal/graphicsdriver/graphics.go
@ -77,7 +77,6 @@ type ImageID int

 type ReplacePixelsArgs struct {
 	Pixels []byte
-	Mask   []byte
 	X      int
 	Y      int
 	Width  int
--- a/internal/processtest/testdata/issue2182.go
+++ b/internal/processtest/testdata/issue2182.go
@ -0,0 +1,93 @@
+// Copyright 2022 The Ebitengine Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//go:build ignore
+// +build ignore
+
+package main
+
+import (
+	"errors"
+	"fmt"
+	"image"
+	"image/color"
+
+	"github.com/hajimehoshi/ebiten/v2"
+	"github.com/hajimehoshi/ebiten/v2/ebitenutil"
+)
+
+var regularTermination = errors.New("regular termination")
+
+var (
+	baseImage    *ebiten.Image
+	derivedImage *ebiten.Image
+)
+
+func init() {
+	const (
+		w = 36
+		h = 40
+	)
+
+	baseImage = ebiten.NewImage(w, h)
+	derivedImage = ebiten.NewImage(w, h)
+
+	baseImage.Fill(color.White)
+	for j := 0; j < h; j++ {
+		for i := 0; i < w; i++ {
+			baseImage.SubImage(image.Rect(i, j, i+1, j+1)).(*ebiten.Image).ReplacePixels([]byte{0, 0, 0, 0xff})
+		}
+	}
+	derivedImage.DrawImage(baseImage, nil)
+}
+
+type Game struct {
+	count int
+}
+
+func (g *Game) Update() error {
+	g.count++
+	if g.count == 16 {
+		return regularTermination
+	}
+	return nil
+}
+
+func (g *Game) Draw(screen *ebiten.Image) {
+	screen.Fill(color.White)
+
+	screen.DrawImage(derivedImage, nil)
+	if g.count >= 8 {
+		if got, want := screen.At(0, 0), (color.RGBA{0, 0, 0, 0xff}); got != want {
+			panic(fmt.Sprintf("got: %v, want: %v", got, want))
+		}
+	}
+
+	// The blow 3 line matters to reproduce #2154.
+	mx, my := ebiten.CursorPosition()
+	msg := fmt.Sprintf("TPS: %.01f; FPS: %.01f; cursor: (%d, %d)", ebiten.CurrentTPS(), ebiten.CurrentFPS(), mx, my)
+	ebitenutil.DebugPrint(screen, msg)
+}
+
+func (g *Game) Layout(outsideWidth, outsideHeight int) (int, int) {
+	return 640, 480
+}
+
+func main() {
+	ebiten.SetWindowTitle("Test")
+
+	if err := ebiten.RunGame(&Game{}); err != nil && err != regularTermination {
+		panic(err)
+	}
+}
--- a/internal/restorable/image.go
+++ b/internal/restorable/image.go
@ -38,11 +38,11 @@ func (p *Pixels) Apply(img *graphicscommand.Image) {
 	p.pixelsRecords.apply(img)
 }

-func (p *Pixels) AddOrReplace(pix []byte, mask []byte, x, y, width, height int) {
+func (p *Pixels) AddOrReplace(pix []byte, x, y, width, height int) {
 	if p.pixelsRecords == nil {
 		p.pixelsRecords = &pixelsRecords{}
 	}
-	p.pixelsRecords.addOrReplace(pix, mask, x, y, width, height)
+	p.pixelsRecords.addOrReplace(pix, x, y, width, height)
 }

 func (p *Pixels) Clear(x, y, width, height int) {
@ -144,7 +144,7 @@ func ensureEmptyImage() *Image {

 	// As emptyImage is the source at clearImage, initialize this with ReplacePixels, not clearImage.
 	// This operation is also important when restoring emptyImage.
-	emptyImage.ReplacePixels(pix, nil, 0, 0, w, h)
+	emptyImage.ReplacePixels(pix, 0, 0, w, h)
 	theImages.add(emptyImage)
 	return emptyImage
 }
@ -267,7 +267,7 @@ func (i *Image) makeStale() {

 // ClearPixels clears the specified region by ReplacePixels.
 func (i *Image) ClearPixels(x, y, width, height int) {
-	i.ReplacePixels(nil, nil, x, y, width, height)
+	i.ReplacePixels(nil, x, y, width, height)
 }

 func (i *Image) needsRestoring() bool {
@ -277,7 +277,7 @@ func (i *Image) needsRestoring() bool {
 // ReplacePixels replaces the image pixels with the given pixels slice.
 //
 // The specified region must not be overlapped with other regions by ReplacePixels.
-func (i *Image) ReplacePixels(pixels []byte, mask []byte, x, y, width, height int) {
+func (i *Image) ReplacePixels(pixels []byte, x, y, width, height int) {
 	if width <= 0 || height <= 0 {
 		panic("restorable: width/height must be positive")
 	}
@ -291,12 +291,12 @@ func (i *Image) ReplacePixels(pixels []byte, mask []byte, x, y, width, height in
 	theImages.makeStaleIfDependingOn(i)

 	if pixels != nil {
-		i.image.ReplacePixels(pixels, mask, x, y, width, height)
+		i.image.ReplacePixels(pixels, x, y, width, height)
 	} else {
 		// TODO: When pixels == nil, we don't have to care the pixel state there. In such cases, the image
 		// accepts only ReplacePixels and not Fill or DrawTriangles.
 		// TODO: Separate Image struct into two: images for only-ReplacePixels, and the others.
-		i.image.ReplacePixels(make([]byte, 4*width*height), nil, x, y, width, height)
+		i.image.ReplacePixels(make([]byte, 4*width*height), x, y, width, height)
 	}

 	if !needsRestoring() || !i.needsRestoring() {
@ -310,7 +310,7 @@ func (i *Image) ReplacePixels(pixels []byte, mask []byte, x, y, width, height in
 			// This function is responsible to copy this.
 			copiedPixels := make([]byte, len(pixels))
 			copy(copiedPixels, pixels)
-			i.basePixels.AddOrReplace(copiedPixels, mask, 0, 0, w, h)
+			i.basePixels.AddOrReplace(copiedPixels, 0, 0, w, h)
 		} else {
 			i.basePixels.Clear(0, 0, w, h)
 		}
@ -334,7 +334,7 @@ func (i *Image) ReplacePixels(pixels []byte, mask []byte, x, y, width, height in
 		// This function is responsible to copy this.
 		copiedPixels := make([]byte, len(pixels))
 		copy(copiedPixels, pixels)
-		i.basePixels.AddOrReplace(copiedPixels, mask, x, y, width, height)
+		i.basePixels.AddOrReplace(copiedPixels, x, y, width, height)
 	} else {
 		i.basePixels.Clear(x, y, width, height)
 	}
@ -490,7 +490,7 @@ func (i *Image) readPixelsFromGPU(graphicsDriver graphicsdriver.Graphics) error
 		return err
 	}
 	i.basePixels = Pixels{}
-	i.basePixels.AddOrReplace(pix, nil, 0, 0, i.width, i.height)
+	i.basePixels.AddOrReplace(pix, 0, 0, i.width, i.height)
 	i.clearDrawTrianglesHistory()
 	i.stale = false
 	return nil
@ -615,7 +615,7 @@ func (i *Image) restore(graphicsDriver graphicsdriver.Graphics) error {
 		if err := gimg.ReadPixels(graphicsDriver, pix); err != nil {
 			return err
 		}
-		i.basePixels.AddOrReplace(pix, nil, 0, 0, w, h)
+		i.basePixels.AddOrReplace(pix, 0, 0, w, h)
 	}

 	i.image = gimg
--- a/internal/restorable/images_test.go
+++ b/internal/restorable/images_test.go
@ -61,7 +61,7 @@ func TestRestore(t *testing.T) {
 	defer img0.Dispose()

 	clr0 := color.RGBA{0x00, 0x00, 0x00, 0xff}
-	img0.ReplacePixels([]byte{clr0.R, clr0.G, clr0.B, clr0.A}, nil, 0, 0, 1, 1)
+	img0.ReplacePixels([]byte{clr0.R, clr0.G, clr0.B, clr0.A}, 0, 0, 1, 1)
 	if err := restorable.ResolveStaleImages(ui.GraphicsDriverForTesting()); err != nil {
 		t.Fatal(err)
 	}
@ -135,7 +135,7 @@ func TestRestoreChain(t *testing.T) {
 		}
 	}()
 	clr := color.RGBA{0x00, 0x00, 0x00, 0xff}
-	imgs[0].ReplacePixels([]byte{clr.R, clr.G, clr.B, clr.A}, nil, 0, 0, 1, 1)
+	imgs[0].ReplacePixels([]byte{clr.R, clr.G, clr.B, clr.A}, 0, 0, 1, 1)
 	for i := 0; i < num-1; i++ {
 		vs := quadVertices(imgs[i], 1, 1, 0, 0)
 		is := graphics.QuadIndices()
@ -180,11 +180,11 @@ func TestRestoreChain2(t *testing.T) {
 	}()

 	clr0 := color.RGBA{0xff, 0x00, 0x00, 0xff}
-	imgs[0].ReplacePixels([]byte{clr0.R, clr0.G, clr0.B, clr0.A}, nil, 0, 0, w, h)
+	imgs[0].ReplacePixels([]byte{clr0.R, clr0.G, clr0.B, clr0.A}, 0, 0, w, h)
 	clr7 := color.RGBA{0x00, 0xff, 0x00, 0xff}
-	imgs[7].ReplacePixels([]byte{clr7.R, clr7.G, clr7.B, clr7.A}, nil, 0, 0, w, h)
+	imgs[7].ReplacePixels([]byte{clr7.R, clr7.G, clr7.B, clr7.A}, 0, 0, w, h)
 	clr8 := color.RGBA{0x00, 0x00, 0xff, 0xff}
-	imgs[8].ReplacePixels([]byte{clr8.R, clr8.G, clr8.B, clr8.A}, nil, 0, 0, w, h)
+	imgs[8].ReplacePixels([]byte{clr8.R, clr8.G, clr8.B, clr8.A}, 0, 0, w, h)

 	is := graphics.QuadIndices()
 	dr := graphicsdriver.Region{
@ -234,7 +234,7 @@ func TestRestoreOverrideSource(t *testing.T) {
 	}()
 	clr0 := color.RGBA{0x00, 0x00, 0x00, 0xff}
 	clr1 := color.RGBA{0x00, 0x00, 0x01, 0xff}
-	img1.ReplacePixels([]byte{clr0.R, clr0.G, clr0.B, clr0.A}, nil, 0, 0, w, h)
+	img1.ReplacePixels([]byte{clr0.R, clr0.G, clr0.B, clr0.A}, 0, 0, w, h)
 	is := graphics.QuadIndices()
 	dr := graphicsdriver.Region{
 		X:      0,
@ -244,7 +244,7 @@ func TestRestoreOverrideSource(t *testing.T) {
 	}
 	img2.DrawTriangles([graphics.ShaderImageNum]*restorable.Image{img1}, [graphics.ShaderImageNum - 1][2]float32{}, quadVertices(img1, w, h, 0, 0), is, affine.ColorMIdentity{}, graphicsdriver.CompositeModeSourceOver, graphicsdriver.FilterNearest, graphicsdriver.AddressUnsafe, dr, graphicsdriver.Region{}, nil, nil, false)
 	img3.DrawTriangles([graphics.ShaderImageNum]*restorable.Image{img2}, [graphics.ShaderImageNum - 1][2]float32{}, quadVertices(img2, w, h, 0, 0), is, affine.ColorMIdentity{}, graphicsdriver.CompositeModeSourceOver, graphicsdriver.FilterNearest, graphicsdriver.AddressUnsafe, dr, graphicsdriver.Region{}, nil, nil, false)
-	img0.ReplacePixels([]byte{clr1.R, clr1.G, clr1.B, clr1.A}, nil, 0, 0, w, h)
+	img0.ReplacePixels([]byte{clr1.R, clr1.G, clr1.B, clr1.A}, 0, 0, w, h)
 	img1.DrawTriangles([graphics.ShaderImageNum]*restorable.Image{img0}, [graphics.ShaderImageNum - 1][2]float32{}, quadVertices(img0, w, h, 0, 0), is, affine.ColorMIdentity{}, graphicsdriver.CompositeModeSourceOver, graphicsdriver.FilterNearest, graphicsdriver.AddressUnsafe, dr, graphicsdriver.Region{}, nil, nil, false)
 	if err := restorable.ResolveStaleImages(ui.GraphicsDriverForTesting()); err != nil {
 		t.Fatal(err)
@ -417,7 +417,7 @@ func TestRestoreComplexGraph(t *testing.T) {
 func newImageFromImage(rgba *image.RGBA) *restorable.Image {
 	s := rgba.Bounds().Size()
 	img := restorable.NewImage(s.X, s.Y, restorable.ImageTypeRegular)
-	img.ReplacePixels(rgba.Pix, nil, 0, 0, s.X, s.Y)
+	img.ReplacePixels(rgba.Pix, 0, 0, s.X, s.Y)
 	return img
 }

@ -491,7 +491,7 @@ func TestReplacePixels(t *testing.T) {
 	for i := range pix {
 		pix[i] = 0xff
 	}
-	img.ReplacePixels(pix, nil, 5, 7, 4, 4)
+	img.ReplacePixels(pix, 5, 7, 4, 4)
 	// Check the region (5, 7)-(9, 11). Outside state is indeterministic.
 	for j := 7; j < 11; j++ {
 		for i := 5; i < 9; i++ {
@ -547,7 +547,7 @@ func TestDrawTrianglesAndReplacePixels(t *testing.T) {
 		Height: 1,
 	}
 	img1.DrawTriangles([graphics.ShaderImageNum]*restorable.Image{img0}, [graphics.ShaderImageNum - 1][2]float32{}, vs, is, affine.ColorMIdentity{}, graphicsdriver.CompositeModeCopy, graphicsdriver.FilterNearest, graphicsdriver.AddressUnsafe, dr, graphicsdriver.Region{}, nil, nil, false)
-	img1.ReplacePixels([]byte{0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff}, nil, 0, 0, 2, 1)
+	img1.ReplacePixels([]byte{0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff}, 0, 0, 2, 1)

 	if err := restorable.ResolveStaleImages(ui.GraphicsDriverForTesting()); err != nil {
 		t.Fatal(err)
@ -618,7 +618,7 @@ func TestReplacePixelsPart(t *testing.T) {

 	img := restorable.NewImage(4, 4, restorable.ImageTypeRegular)
 	// This doesn't make the image stale. Its base pixels are available.
-	img.ReplacePixels(pix, nil, 1, 1, 2, 2)
+	img.ReplacePixels(pix, 1, 1, 2, 2)

 	cases := []struct {
 		i    int
@ -693,7 +693,7 @@ func TestReplacePixelsOnly(t *testing.T) {
 	defer img1.Dispose()

 	for i := 0; i < w*h; i += 5 {
-		img0.ReplacePixels([]byte{1, 2, 3, 4}, nil, i%w, i/w, 1, 1)
+		img0.ReplacePixels([]byte{1, 2, 3, 4}, i%w, i/w, 1, 1)
 	}

 	vs := quadVertices(img0, 1, 1, 0, 0)
@ -705,7 +705,7 @@ func TestReplacePixelsOnly(t *testing.T) {
 		Height: 1,
 	}
 	img1.DrawTriangles([graphics.ShaderImageNum]*restorable.Image{img0}, [graphics.ShaderImageNum - 1][2]float32{}, vs, is, affine.ColorMIdentity{}, graphicsdriver.CompositeModeCopy, graphicsdriver.FilterNearest, graphicsdriver.AddressUnsafe, dr, graphicsdriver.Region{}, nil, nil, false)
-	img0.ReplacePixels([]byte{5, 6, 7, 8}, nil, 0, 0, 1, 1)
+	img0.ReplacePixels([]byte{5, 6, 7, 8}, 0, 0, 1, 1)

 	// BasePixelsForTesting is available without GPU accessing.
 	for j := 0; j < h; j++ {
@ -747,14 +747,14 @@ func TestReadPixelsFromVolatileImage(t *testing.T) {
 	src := restorable.NewImage(w, h, restorable.ImageTypeRegular)

 	// First, make sure that dst has pixels
-	dst.ReplacePixels(make([]byte, 4*w*h), nil, 0, 0, w, h)
+	dst.ReplacePixels(make([]byte, 4*w*h), 0, 0, w, h)

 	// Second, draw src to dst. If the implementation is correct, dst becomes stale.
 	pix := make([]byte, 4*w*h)
 	for i := range pix {
 		pix[i] = 0xff
 	}
-	src.ReplacePixels(pix, nil, 0, 0, w, h)
+	src.ReplacePixels(pix, 0, 0, w, h)
 	vs := quadVertices(src, 1, 1, 0, 0)
 	is := graphics.QuadIndices()
 	dr := graphicsdriver.Region{
@ -791,7 +791,7 @@ func TestAllowReplacePixelsAfterDrawTriangles(t *testing.T) {
 		Height: h,
 	}
 	dst.DrawTriangles([graphics.ShaderImageNum]*restorable.Image{src}, [graphics.ShaderImageNum - 1][2]float32{}, vs, is, affine.ColorMIdentity{}, graphicsdriver.CompositeModeSourceOver, graphicsdriver.FilterNearest, graphicsdriver.AddressUnsafe, dr, graphicsdriver.Region{}, nil, nil, false)
-	dst.ReplacePixels(make([]byte, 4*w*h), nil, 0, 0, w, h)
+	dst.ReplacePixels(make([]byte, 4*w*h), 0, 0, w, h)
 	// ReplacePixels for a whole image doesn't panic.
 }

@ -815,7 +815,7 @@ func TestDisallowReplacePixelsForPartAfterDrawTriangles(t *testing.T) {
 		Height: h,
 	}
 	dst.DrawTriangles([graphics.ShaderImageNum]*restorable.Image{src}, [graphics.ShaderImageNum - 1][2]float32{}, vs, is, affine.ColorMIdentity{}, graphicsdriver.CompositeModeSourceOver, graphicsdriver.FilterNearest, graphicsdriver.AddressUnsafe, dr, graphicsdriver.Region{}, nil, nil, false)
-	dst.ReplacePixels(make([]byte, 4), nil, 0, 0, 1, 1)
+	dst.ReplacePixels(make([]byte, 4), 0, 0, 1, 1)
 }

 func TestExtend(t *testing.T) {
@ -837,7 +837,7 @@ func TestExtend(t *testing.T) {
 		}
 	}

-	orig.ReplacePixels(pix, nil, 0, 0, w, h)
+	orig.ReplacePixels(pix, 0, 0, w, h)
 	extended := orig.Extend(w*2, h*2) // After this, orig is already disposed.

 	for j := 0; j < h*2; j++ {
@ -860,13 +860,13 @@ func TestExtend(t *testing.T) {
 func TestClearPixels(t *testing.T) {
 	const w, h = 16, 16
 	img := restorable.NewImage(w, h, restorable.ImageTypeRegular)
-	img.ReplacePixels(make([]byte, 4*4*4), nil, 0, 0, 4, 4)
-	img.ReplacePixels(make([]byte, 4*4*4), nil, 4, 0, 4, 4)
+	img.ReplacePixels(make([]byte, 4*4*4), 0, 0, 4, 4)
+	img.ReplacePixels(make([]byte, 4*4*4), 4, 0, 4, 4)
 	img.ClearPixels(0, 0, 4, 4)
 	img.ClearPixels(4, 0, 4, 4)

 	// After clearing, the regions will be available again.
-	img.ReplacePixels(make([]byte, 4*8*4), nil, 0, 0, 8, 4)
+	img.ReplacePixels(make([]byte, 4*8*4), 0, 0, 8, 4)
 }

 func TestMutateSlices(t *testing.T) {
@ -880,7 +880,7 @@ func TestMutateSlices(t *testing.T) {
 		pix[4*i+2] = byte(i)
 		pix[4*i+3] = 0xff
 	}
-	src.ReplacePixels(pix, nil, 0, 0, w, h)
+	src.ReplacePixels(pix, 0, 0, w, h)

 	vs := quadVertices(src, w, h, 0, 0)
 	is := make([]uint16, len(graphics.QuadIndices()))
@ -937,7 +937,7 @@ func TestOverlappedPixels(t *testing.T) {
 			pix0[idx+3] = 0xff
 		}
 	}
-	dst.ReplacePixels(pix0, nil, 0, 0, 2, 2)
+	dst.ReplacePixels(pix0, 0, 0, 2, 2)

 	pix1 := make([]byte, 4*2*2)
 	for j := 0; j < 2; j++ {
@ -949,7 +949,7 @@ func TestOverlappedPixels(t *testing.T) {
 			pix1[idx+3] = 0xff
 		}
 	}
-	dst.ReplacePixels(pix1, nil, 1, 1, 2, 2)
+	dst.ReplacePixels(pix1, 1, 1, 2, 2)

 	wantColors := []color.RGBA{
 		{0xff, 0, 0, 0xff},
@ -978,7 +978,7 @@ func TestOverlappedPixels(t *testing.T) {
 		}
 	}

-	dst.ReplacePixels(nil, nil, 1, 0, 2, 2)
+	dst.ReplacePixels(nil, 1, 0, 2, 2)

 	wantColors = []color.RGBA{
 		{0xff, 0, 0, 0xff},
@ -1017,7 +1017,7 @@ func TestOverlappedPixels(t *testing.T) {
 			pix2[idx+3] = 0xff
 		}
 	}
-	dst.ReplacePixels(pix2, nil, 1, 1, 2, 2)
+	dst.ReplacePixels(pix2, 1, 1, 2, 2)

 	wantColors = []color.RGBA{
 		{0xff, 0, 0, 0xff},
@ -1067,151 +1067,3 @@ func TestOverlappedPixels(t *testing.T) {
 		}
 	}
 }
-
-func TestReplacePixelsWithMask(t *testing.T) {
-	dst := restorable.NewImage(3, 3, restorable.ImageTypeRegular)
-
-	pix0 := make([]byte, 4*2*2)
-	for j := 0; j < 2; j++ {
-		for i := 0; i < 2; i++ {
-			idx := 4 * (j*2 + i)
-			pix0[idx] = 0xff
-			pix0[idx+1] = 0
-			pix0[idx+2] = 0
-			pix0[idx+3] = 0xff
-		}
-	}
-	dst.ReplacePixels(pix0, nil, 0, 0, 2, 2)
-
-	pix1 := make([]byte, 4*2*2)
-	for j := 0; j < 2; j++ {
-		for i := 0; i < 2; i++ {
-			idx := 4 * (j*2 + i)
-			pix1[idx] = 0
-			pix1[idx+1] = 0xff
-			pix1[idx+2] = 0
-			pix1[idx+3] = 0xff
-		}
-	}
-
-	mask1 := []byte{0b00001110}
-	dst.ReplacePixels(pix1, mask1, 1, 1, 2, 2)
-
-	wantColors := []color.RGBA{
-		{0xff, 0, 0, 0xff},
-		{0xff, 0, 0, 0xff},
-		{0, 0, 0, 0},
-
-		{0xff, 0, 0, 0xff},
-		{0xff, 0, 0, 0xff},
-		{0, 0xff, 0, 0xff},
-
-		{0, 0, 0, 0},
-		{0, 0xff, 0, 0xff},
-		{0, 0xff, 0, 0xff},
-	}
-	for j := 0; j < 3; j++ {
-		for i := 0; i < 3; i++ {
-			r, g, b, a, err := dst.At(ui.GraphicsDriverForTesting(), i, j)
-			if err != nil {
-				t.Fatal(err)
-			}
-			got := color.RGBA{r, g, b, a}
-			want := wantColors[3*j+i]
-			if got != want {
-				t.Errorf("color at (%d, %d): got %v, want: %v", i, j, got, want)
-			}
-		}
-	}
-
-	dst.ReplacePixels(nil, nil, 1, 0, 2, 2)
-
-	wantColors = []color.RGBA{
-		{0xff, 0, 0, 0xff},
-		{0, 0, 0, 0},
-		{0, 0, 0, 0},
-
-		{0xff, 0, 0, 0xff},
-		{0, 0, 0, 0},
-		{0, 0, 0, 0},
-
-		{0, 0, 0, 0},
-		{0, 0xff, 0, 0xff},
-		{0, 0xff, 0, 0xff},
-	}
-	for j := 0; j < 3; j++ {
-		for i := 0; i < 3; i++ {
-			r, g, b, a, err := dst.At(ui.GraphicsDriverForTesting(), i, j)
-			if err != nil {
-				t.Fatal(err)
-			}
-			got := color.RGBA{r, g, b, a}
-			want := wantColors[3*j+i]
-			if got != want {
-				t.Errorf("color at (%d, %d): got %v, want: %v", i, j, got, want)
-			}
-		}
-	}
-
-	// Update the same region with pix1/mask1.
-	pix2 := make([]byte, 4*2*2)
-	for j := 0; j < 2; j++ {
-		for i := 0; i < 2; i++ {
-			idx := 4 * (j*2 + i)
-			pix2[idx] = 0
-			pix2[idx+1] = 0
-			pix2[idx+2] = 0xff
-			pix2[idx+3] = 0xff
-		}
-	}
-	mask2 := []byte{0b00000111}
-	dst.ReplacePixels(pix2, mask2, 1, 1, 2, 2)
-
-	wantColors = []color.RGBA{
-		{0xff, 0, 0, 0xff},
-		{0, 0, 0, 0},
-		{0, 0, 0, 0},
-
-		{0xff, 0, 0, 0xff},
-		{0, 0, 0xff, 0xff},
-		{0, 0, 0xff, 0xff},
-
-		{0, 0, 0, 0},
-		{0, 0, 0xff, 0xff},
-		{0, 0xff, 0, 0xff},
-	}
-	for j := 0; j < 3; j++ {
-		for i := 0; i < 3; i++ {
-			r, g, b, a, err := dst.At(ui.GraphicsDriverForTesting(), i, j)
-			if err != nil {
-				t.Fatal(err)
-			}
-			got := color.RGBA{r, g, b, a}
-			want := wantColors[3*j+i]
-			if got != want {
-				t.Errorf("color at (%d, %d): got %v, want: %v", i, j, got, want)
-			}
-		}
-	}
-
-	if err := restorable.ResolveStaleImages(ui.GraphicsDriverForTesting()); err != nil {
-		t.Fatal(err)
-	}
-	if err := restorable.RestoreIfNeeded(ui.GraphicsDriverForTesting()); err != nil {
-		t.Fatal(err)
-	}
-
-	for j := 0; j < 3; j++ {
-		for i := 0; i < 3; i++ {
-			r, g, b, a, err := dst.At(ui.GraphicsDriverForTesting(), i, j)
-			if err != nil {
-				t.Fatal(err)
-			}
-			got := color.RGBA{r, g, b, a}
-			want := wantColors[3*j+i]
-			if got != want {
-				t.Errorf("color at (%d, %d): got %v, want: %v", i, j, got, want)
-			}
-		}
-	}
-}
--- a/internal/restorable/rect.go
+++ b/internal/restorable/rect.go
@ -24,7 +24,6 @@ import (
 type pixelsRecord struct {
 	rect image.Rectangle
 	pix  []byte
-	mask []byte
 }

 func (p *pixelsRecord) clearIfOverlapped(rect image.Rectangle) {
@ -43,40 +42,11 @@ func (p *pixelsRecord) clearIfOverlapped(rect image.Rectangle) {
 	}
 }

-func (p *pixelsRecord) merge(pix []byte, mask []byte) {
-	if len(p.pix) != len(pix) {
-		panic(fmt.Sprintf("restorable: len(p.pix) (%d) and len(pix) (%d) must match but not", len(p.pix), len(pix)))
-	}
-
-	if mask == nil {
-		p.pix = pix
-		return
-	}
-
-	if p.mask == nil {
-		p.mask = mask
-	}
-	if len(p.mask) != len(mask) {
-		panic(fmt.Sprintf("restorable: len(p.mask) (%d) and len(mask) (%d) must match but not", len(p.mask), len(mask)))
-	}
-
-	for i := 0; i < len(p.pix)/4; i++ {
-		if mask[i/8]>>(i%8)&1 == 0 {
-			continue
-		}
-		p.mask[i/8] |= 1 << (i % 8)
-		copy(p.pix[4*i:4*(i+1)], pix[4*i:4*(i+1)])
-	}
-}
-
 func (p *pixelsRecord) at(x, y int) (r, g, b, a byte, ok bool) {
 	if !image.Pt(x, y).In(p.rect) {
 		return 0, 0, 0, 0, false
 	}
 	idx := ((y-p.rect.Min.Y)*p.rect.Dx() + (x - p.rect.Min.X))
-	if p.mask != nil && p.mask[idx/8]>>(idx%8)&1 == 0 {
-		return 0, 0, 0, 0, false
-	}
 	return p.pix[4*idx], p.pix[4*idx+1], p.pix[4*idx+2], p.pix[4*idx+3], true
 }

@ -84,7 +54,7 @@ type pixelsRecords struct {
 	records []*pixelsRecord
 }

-func (pr *pixelsRecords) addOrReplace(pixels []byte, mask []byte, x, y, width, height int) {
+func (pr *pixelsRecords) addOrReplace(pixels []byte, x, y, width, height int) {
 	if len(pixels) != 4*width*height {
 		msg := fmt.Sprintf("restorable: len(pixels) must be 4*%d*%d = %d but %d", width, height, 4*width*height, len(pixels))
 		if pixels == nil {
@ -94,29 +64,6 @@ func (pr *pixelsRecords) addOrReplace(pixels []byte, mask []byte, x, y, width, h
 	}

 	rect := image.Rect(x, y, x+width, y+height)
-	if mask != nil {
-		// If a mask is specified, try merging the records.
-		var merged bool
-		for idx := len(pr.records) - 1; idx >= 0; idx-- {
-			if r := pr.records[idx]; r.rect.Overlaps(rect) {
-				if r.rect == rect {
-					r.merge(pixels, mask)
-					merged = true
-				}
-				// If there is an overlap with other regions in the existing records,
-				// give up modifying them and just add a record.
-				break
-			}
-		}
-		if !merged {
-			pr.records = append(pr.records, &pixelsRecord{
-				rect: rect,
-				pix:  pixels,
-				mask: mask,
-			})
-		}
-		return
-	}

 	// Remove or update the duplicated records first.
 	var n int
@ -171,6 +118,6 @@ func (pr *pixelsRecords) at(i, j int) (r, g, b, a byte, ok bool) {
 func (pr *pixelsRecords) apply(img *graphicscommand.Image) {
 	// TODO: Isn't this too heavy? Can we merge the operations?
 	for _, r := range pr.records {
-		img.ReplacePixels(r.pix, r.mask, r.rect.Min.X, r.rect.Min.Y, r.rect.Dx(), r.rect.Dy())
+		img.ReplacePixels(r.pix, r.rect.Min.X, r.rect.Min.Y, r.rect.Dx(), r.rect.Dy())
 	}
 }
--- a/internal/restorable/shader_test.go
+++ b/internal/restorable/shader_test.go
@ -90,7 +90,7 @@ func TestShaderChain(t *testing.T) {
 		imgs = append(imgs, img)
 	}

-	imgs[0].ReplacePixels([]byte{0xff, 0, 0, 0xff}, nil, 0, 0, 1, 1)
+	imgs[0].ReplacePixels([]byte{0xff, 0, 0, 0xff}, 0, 0, 1, 1)

 	s := restorable.NewShader(etesting.ShaderProgramImages(1))
 	for i := 0; i < num-1; i++ {
@ -124,9 +124,9 @@ func TestShaderMultipleSources(t *testing.T) {
 	for i := range srcs {
 		srcs[i] = restorable.NewImage(1, 1, restorable.ImageTypeRegular)
 	}
-	srcs[0].ReplacePixels([]byte{0x40, 0, 0, 0xff}, nil, 0, 0, 1, 1)
-	srcs[1].ReplacePixels([]byte{0, 0x80, 0, 0xff}, nil, 0, 0, 1, 1)
-	srcs[2].ReplacePixels([]byte{0, 0, 0xc0, 0xff}, nil, 0, 0, 1, 1)
+	srcs[0].ReplacePixels([]byte{0x40, 0, 0, 0xff}, 0, 0, 1, 1)
+	srcs[1].ReplacePixels([]byte{0, 0x80, 0, 0xff}, 0, 0, 1, 1)
+	srcs[2].ReplacePixels([]byte{0, 0, 0xc0, 0xff}, 0, 0, 1, 1)

 	dst := restorable.NewImage(1, 1, restorable.ImageTypeRegular)

@ -163,7 +163,7 @@ func TestShaderMultipleSourcesOnOneTexture(t *testing.T) {
 		0x40, 0, 0, 0xff,
 		0, 0x80, 0, 0xff,
 		0, 0, 0xc0, 0xff,
-	}, nil, 0, 0, 3, 1)
+	}, 0, 0, 3, 1)
 	srcs := [graphics.ShaderImageNum]*restorable.Image{src, src, src}

 	dst := restorable.NewImage(1, 1, restorable.ImageTypeRegular)