diff --git a/internal/atlas/image.go b/internal/atlas/image.go
index 3f224a9a5..fddc1662b 100644
--- a/internal/atlas/image.go
+++ b/internal/atlas/image.go
@@ -81,6 +81,9 @@ type backend struct {
 	// restorable is an atlas on which there might be multiple images.
 	restorable *restorable.Image
 
+	width  int
+	height int
+
 	// page is an atlas map. Each part is called a node.
 	// If page is nil, the backend's image is isolated and not on an atlas.
 	page *packing.Page
@@ -107,6 +110,8 @@ func (b *backend) tryAlloc(width, height int) (*packing.Node, bool) {
 
 	w, h := b.page.Size()
 	b.restorable = b.restorable.Extend(w, h)
+	b.width = w
+	b.height = h
 
 	return n, true
 }
@@ -487,7 +492,7 @@ func (i *Image) writePixels(pix []byte, region image.Rectangle) {
 		pix2 := graphics.NewManagedBytes(len(pix), func(bs []byte) {
 			copy(bs, pix)
 		})
-		i.backend.restorable.WritePixels(pix2, region)
+		i.backend.writePixels(pix2, region)
 		return
 	}
 
@@ -516,7 +521,17 @@ func (i *Image) writePixels(pix []byte, region image.Rectangle) {
 			copy(bs[4*j*r.Dx():], pix[4*j*region.Dx():4*(j+1)*region.Dx()])
 		}
 	})
-	i.backend.restorable.WritePixels(pixb, r)
+	i.backend.writePixels(pixb, r)
+}
+
+func (b *backend) writePixels(pixels *graphics.ManagedBytes, region image.Rectangle) {
+	if region.Dx() <= 0 || region.Dy() <= 0 {
+		panic("atlas: width/height must be positive")
+	}
+	if !region.In(image.Rect(0, 0, b.width, b.height)) {
+		panic(fmt.Sprintf("atlas: out of range %v", region))
+	}
+	b.restorable.Image.WritePixels(pixels, region)
 }
 
 // ReadPixels reads pixels on the given region to the given slice pixels.
@@ -667,6 +682,8 @@ func (i *Image) allocate(forbiddenBackends []*backend, asSource bool) {
 		// A screen image doesn't have a padding.
 		i.backend = &backend{
 			restorable: restorable.NewImage(i.width, i.height, true),
+			width:      i.width,
+			height:     i.height,
 		}
 		theBackends = append(theBackends, i.backend)
 		return
@@ -682,6 +699,8 @@ func (i *Image) allocate(forbiddenBackends []*backend, asSource bool) {
 
 		i.backend = &backend{
 			restorable: restorable.NewImage(wp, hp, false),
+			width:      wp,
+			height:     hp,
 			source:     asSource && i.imageType == ImageTypeRegular,
 		}
 		theBackends = append(theBackends, i.backend)
@@ -728,6 +747,8 @@ loop:
 
 	b := &backend{
 		restorable: restorable.NewImage(width, height, false),
+		width:      width,
+		height:     height,
 		page:       packing.NewPage(width, height, maxSize),
 		source:     asSource,
 	}
diff --git a/internal/restorable/image.go b/internal/restorable/image.go
index c61781c47..48f06bda5 100644
--- a/internal/restorable/image.go
+++ b/internal/restorable/image.go
@@ -15,7 +15,6 @@
 package restorable
 
 import (
-	"fmt"
 	"image"
 
 	"github.com/hajimehoshi/ebiten/v2/internal/graphics"
@@ -101,18 +100,3 @@ func (i *Image) ClearPixels(region image.Rectangle) {
 	}
 	clearImage(i.Image, region.Intersect(image.Rect(0, 0, i.width, i.height)))
 }
-
-// WritePixels replaces the image pixels with the given pixels slice.
-//
-// The specified region must not be overlapped with other regions by WritePixels.
-func (i *Image) WritePixels(pixels *graphics.ManagedBytes, region image.Rectangle) {
-	if region.Dx() <= 0 || region.Dy() <= 0 {
-		panic("restorable: width/height must be positive")
-	}
-	w, h := i.width, i.height
-	if !region.In(image.Rect(0, 0, w, h)) {
-		panic(fmt.Sprintf("restorable: out of range %v", region))
-	}
-
-	i.Image.WritePixels(pixels, region)
-}