diff --git a/imagedumper_desktop.go b/imagedumper_desktop.go
index 655cc9e78..a124458ac 100644
--- a/imagedumper_desktop.go
+++ b/imagedumper_desktop.go
@@ -20,10 +20,8 @@ package ebiten
 
 import (
 	"fmt"
-	"image"
 	"io/ioutil"
 	"os"
-	"path/filepath"
 	"time"
 
 	"github.com/hajimehoshi/ebiten/internal/png"
@@ -94,24 +92,8 @@ func dumpInternalImages() error {
 		return err
 	}
 
-	dump := func(img image.Image, index int) error {
-		filename := filepath.Join(dir, fmt.Sprintf("%d.png", index))
-		f, err := os.Create(filename)
-		if err != nil {
-			return err
-		}
-		defer f.Close()
-
-		if err := png.Encode(f, img); err != nil {
-			return err
-		}
-		return nil
-	}
-
-	for i, img := range shareable.Images() {
-		if err := dump(img, i); err != nil {
-			return err
-		}
+	if err := shareable.DumpImages(dir); err != nil {
+		return err
 	}
 
 	if _, err := fmt.Fprintf(os.Stderr, "Dumped the internal images at: %s\n", dir); err != nil {
diff --git a/internal/graphicscommand/image.go b/internal/graphicscommand/image.go
index 725b2d07e..e842cf096 100644
--- a/internal/graphicscommand/image.go
+++ b/internal/graphicscommand/image.go
@@ -15,9 +15,15 @@
 package graphicscommand
 
 import (
+	"fmt"
+	"image"
+	"os"
+	"path/filepath"
+
 	"github.com/hajimehoshi/ebiten/internal/affine"
 	"github.com/hajimehoshi/ebiten/internal/driver"
 	"github.com/hajimehoshi/ebiten/internal/graphics"
+	"github.com/hajimehoshi/ebiten/internal/png"
 )
 
 type lastCommand int
@@ -170,3 +176,23 @@ func (i *Image) IsInvalidated() bool {
 	}
 	return i.image.IsInvalidated()
 }
+
+// DumpImages dumps the image to the specified directory.
+//
+// This is for testing usage.
+func (i *Image) DumpAt(dir string) error {
+	f, err := os.Create(filepath.Join(dir, fmt.Sprintf("%d.png", i.id)))
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+
+	if err := png.Encode(f, &image.RGBA{
+		Pix:    i.Pixels(),
+		Stride: 4 * i.width,
+		Rect:   image.Rect(0, 0, i.width, i.height),
+	}); err != nil {
+		return err
+	}
+	return nil
+}
diff --git a/internal/restorable/images.go b/internal/restorable/images.go
index 4c91bb369..89e637f8e 100644
--- a/internal/restorable/images.go
+++ b/internal/restorable/images.go
@@ -15,8 +15,6 @@
 package restorable
 
 import (
-	"image"
-
 	"github.com/hajimehoshi/ebiten/internal/graphicscommand"
 )
 
@@ -90,11 +88,10 @@ func RestoreIfNeeded() error {
 	return theImages.restore()
 }
 
-// Images returns all the current images.
+// DumpImages dumps all the current images to the specified directory.
 //
 // This is for testing usage.
-func Images() []image.Image {
-	var imgs []image.Image
+func DumpImages(dir string) error {
 	for img := range theImages.images {
 		if img.volatile {
 			continue
@@ -102,25 +99,11 @@ func Images() []image.Image {
 		if img.screen {
 			continue
 		}
-
-		w, h := img.Size()
-		pix := make([]byte, 4*w*h)
-		for j := 0; j < h; j++ {
-			for i := 0; i < w; i++ {
-				r, g, b, a := img.At(i, j)
-				pix[4*(i+j*w)] = r
-				pix[4*(i+j*w)+1] = g
-				pix[4*(i+j*w)+2] = b
-				pix[4*(i+j*w)+3] = a
-			}
+		if err := img.image.DumpAt(dir); err != nil {
+			return err
 		}
-		imgs = append(imgs, &image.RGBA{
-			Pix:    pix,
-			Stride: 4 * w,
-			Rect:   image.Rect(0, 0, w, h),
-		})
 	}
-	return imgs
+	return nil
 }
 
 // add adds img to the images.
diff --git a/internal/shareable/shareable.go b/internal/shareable/shareable.go
index 8cb40a0ca..afc622ccc 100644
--- a/internal/shareable/shareable.go
+++ b/internal/shareable/shareable.go
@@ -16,7 +16,6 @@ package shareable
 
 import (
 	"fmt"
-	"image"
 	"runtime"
 	"sync"
 
@@ -528,10 +527,10 @@ func RestoreIfNeeded() error {
 	return restorable.RestoreIfNeeded()
 }
 
-func Images() []image.Image {
+func DumpImages(dir string) error {
 	backendsM.Lock()
 	defer backendsM.Unlock()
-	return restorable.Images()
+	return restorable.DumpImages(dir)
 }
 
 func Error() error {