diff --git a/ebitenutil/debugprint.go b/ebitenutil/debugprint.go
index ee74d1375..dd5cab429 100644
--- a/ebitenutil/debugprint.go
+++ b/ebitenutil/debugprint.go
@@ -19,6 +19,7 @@ package ebitenutil
 import (
 	"github.com/hajimehoshi/ebiten"
 	"github.com/hajimehoshi/ebiten/internal/assets"
+	"image"
 	"image/color"
 	"math"
 )
@@ -46,11 +47,11 @@ func (d *debugPrintState) drawText(rt *ebiten.Image, str string, x, y int, c col
 		}
 		code := int(c)
 		const xCharNum = assets.TextImageWidth / assets.TextImageCharWidth
-		srcX := float64(code%xCharNum) * assets.TextImageCharWidth
-		srcY := float64(code/xCharNum) * assets.TextImageCharHeight
+		srcX := (code % xCharNum) * assets.TextImageCharWidth
+		srcY := (code / xCharNum) * assets.TextImageCharHeight
 		parts = append(parts, ebiten.ImagePart{
-			Dst: ebiten.Rect{float64(locationX), float64(locationY), assets.TextImageCharWidth, assets.TextImageCharHeight},
-			Src: ebiten.Rect{srcX, srcY, assets.TextImageCharWidth, assets.TextImageCharHeight},
+			Dst: image.Rect(locationX, locationY, locationX+assets.TextImageCharWidth, locationY+assets.TextImageCharHeight),
+			Src: image.Rect(srcX, srcY, srcX+assets.TextImageCharWidth, srcY+assets.TextImageCharHeight),
 		})
 		locationX += assets.TextImageCharWidth
 	}
diff --git a/ebitenutil/gif.go b/ebitenutil/gif.go
index cd4643151..b35059315 100644
--- a/ebitenutil/gif.go
+++ b/ebitenutil/gif.go
@@ -40,7 +40,8 @@ func (r *recorder) update(screen *ebiten.Image) error {
 		return nil
 	}
 	img := image.NewPaletted(screen.Bounds(), palette.Plan9)
-	draw.Draw(img, img.Bounds(), screen, screen.Bounds().Min, draw.Over)
+	// TODO: This is too slow.
+	draw.Draw(img, img.Bounds(), screen, screen.Bounds().Min, draw.Src)
 	r.gif.Image[r.currentFrame] = img
 	// The actual FPS is 60, but GIF can't have such FPS. Set 50 FPS instead.
 	r.gif.Delay[r.currentFrame] = 2
diff --git a/example/alphablending/main.go b/example/alphablending/main.go
index d9eb0f510..44accb72e 100644
--- a/example/alphablending/main.go
+++ b/example/alphablending/main.go
@@ -87,9 +87,9 @@ func main() {
 	if err != nil {
 		log.Fatal(err)
 	}
-	update := update
-	// f, _ := os.Create("out.gif")
-	// update = ebitenutil.RecordScreenAsGIF(update, f, 100)
+	//update := update
+	//f, _ := os.Create("out.gif")
+	//update = ebitenutil.RecordScreenAsGIF(update, f, 100)
 	if err := ebiten.Run(update, screenWidth, screenHeight, 2, "Alpha Blending (Ebiten Demo)"); err != nil {
 		log.Fatal(err)
 	}
diff --git a/example/blocks/blocks/font.go b/example/blocks/blocks/font.go
index 8897ce10b..5e58886a0 100644
--- a/example/blocks/blocks/font.go
+++ b/example/blocks/blocks/font.go
@@ -18,6 +18,7 @@ package blocks
 
 import (
 	"github.com/hajimehoshi/ebiten"
+	"image"
 	"image/color"
 	"math"
 )
@@ -45,11 +46,11 @@ func drawText(rt *ebiten.Image, images *Images, str string, ox, oy, scale int, c
 			continue
 		}
 		code := int(c)
-		x := float64(code%16) * charWidth
-		y := float64((code-32)/16) * charHeight
+		x := (code % 16) * charWidth
+		y := ((code - 32) / 16) * charHeight
 		parts = append(parts, ebiten.ImagePart{
-			Dst: ebiten.Rect{float64(locationX), float64(locationY), charWidth, charHeight},
-			Src: ebiten.Rect{x, y, charWidth, charHeight},
+			Dst: image.Rect(locationX, locationY, locationX+charWidth, locationY+charHeight),
+			Src: image.Rect(x, y, x+charWidth, y+charHeight),
 		})
 		locationX += charWidth
 	}
diff --git a/example/blocks/blocks/piece.go b/example/blocks/blocks/piece.go
index fb6c3ff10..0cb876502 100644
--- a/example/blocks/blocks/piece.go
+++ b/example/blocks/blocks/piece.go
@@ -18,6 +18,7 @@ package blocks
 
 import (
 	"github.com/hajimehoshi/ebiten"
+	"image"
 )
 
 func init() {
@@ -145,10 +146,11 @@ func drawBlocks(r *ebiten.Image, images *Images, blocks [][]BlockType, geo ebite
 			if block == BlockTypeNone {
 				continue
 			}
-			locationX := float64(i * blockWidth)
-			locationY := float64(j * blockHeight)
-			dst := ebiten.Rect{locationX, locationY, blockWidth, blockHeight}
-			src := ebiten.Rect{float64(int(block)-1) * blockWidth, 0, blockWidth, blockHeight}
+			locationX := i * blockWidth
+			locationY := j * blockHeight
+			dst := image.Rect(locationX, locationY, locationX+blockWidth, locationY+blockHeight)
+			srcX := (int(block) - 1) * blockWidth
+			src := image.Rect(srcX, 0, srcX+blockWidth, blockHeight)
 			parts = append(parts, ebiten.ImagePart{dst, src})
 		}
 	}
diff --git a/example/blocks/blocks/titlescene.go b/example/blocks/blocks/titlescene.go
index cb0f54481..743464242 100644
--- a/example/blocks/blocks/titlescene.go
+++ b/example/blocks/blocks/titlescene.go
@@ -18,6 +18,7 @@ package blocks
 
 import (
 	"github.com/hajimehoshi/ebiten"
+	"image"
 	"image/color"
 )
 
@@ -58,9 +59,11 @@ func drawTitleBackground(r *ebiten.Image, images *Images, c int) {
 	parts := []ebiten.ImagePart{}
 	for j := -1; j < ScreenHeight/imageHeight+1; j++ {
 		for i := 0; i < ScreenWidth/imageWidth+1; i++ {
+			dstX := i * imageWidth
+			dstY := j * imageHeight
 			parts = append(parts, ebiten.ImagePart{
-				Dst: ebiten.Rect{float64(i * imageWidth), float64(j * imageHeight), imageWidth, imageHeight},
-				Src: ebiten.Rect{0, 0, imageWidth, imageHeight},
+				Dst: image.Rect(dstX, dstY, dstX+imageWidth, dstY+imageHeight),
+				Src: image.Rect(0, 0, imageWidth, imageHeight),
 			})
 		}
 	}
diff --git a/example/perspective/main.go b/example/perspective/main.go
index 44afbe4e0..b9165af28 100644
--- a/example/perspective/main.go
+++ b/example/perspective/main.go
@@ -19,6 +19,7 @@ package main
 import (
 	"github.com/hajimehoshi/ebiten"
 	"github.com/hajimehoshi/ebiten/ebitenutil"
+	"image"
 	_ "image/jpeg"
 	"log"
 )
@@ -36,11 +37,11 @@ func Update(screen *ebiten.Image) error {
 	parts := []ebiten.ImagePart{}
 	w, h := gophersImage.Size()
 	for i := 0; i < h; i++ {
-		width := float64(w) + float64(i)*0.75
-		x := float64(h-i) * 0.75 / 2
+		width := w + i*3/4
+		x := ((h - i) * 3 / 4) / 2
 		part := ebiten.ImagePart{
-			Dst: ebiten.Rect{x, float64(i), width, 1},
-			Src: ebiten.Rect{0, float64(i), float64(w), 1},
+			Dst: image.Rect(x, i, x+width, i+1),
+			Src: image.Rect(0, i, w, i+1),
 		}
 		parts = append(parts, part)
 	}
diff --git a/graphics.go b/graphics.go
index e3ab0f63d..4e7935bf7 100644
--- a/graphics.go
+++ b/graphics.go
@@ -18,29 +18,22 @@ package ebiten
 
 import (
 	"github.com/hajimehoshi/ebiten/internal/opengl"
+	"image"
 )
 
-// A Rect represents a rectangle.
-type Rect struct {
-	X      float64
-	Y      float64
-	Width  float64
-	Height float64
-}
-
 // An ImagePart represents a part of an image.
 type ImagePart struct {
-	Dst Rect
-	Src Rect
+	Dst image.Rectangle
+	Src image.Rectangle
 }
 
 // DrawWholeImage draws the whole image.
-func DrawWholeImage(target *Image, image *Image, geo GeometryMatrix, color ColorMatrix) error {
-	w, h := image.Size()
+func DrawWholeImage(target *Image, img *Image, geo GeometryMatrix, color ColorMatrix) error {
+	w, h := img.Size()
 	parts := []ImagePart{
-		{Rect{0, 0, float64(w), float64(h)}, Rect{0, 0, float64(w), float64(h)}},
+		{image.Rect(0, 0, w, h), image.Rect(0, 0, w, h)},
 	}
-	return target.DrawImage(image, parts, geo, color)
+	return target.DrawImage(img, parts, geo, color)
 }
 
 // Filter represents the type of filter to be used when an image is maginified or minified.
diff --git a/graphicscontext.go b/graphicscontext.go
index 353a2e267..d40a378c9 100644
--- a/graphicscontext.go
+++ b/graphicscontext.go
@@ -18,6 +18,7 @@ package ebiten
 
 import (
 	"github.com/hajimehoshi/ebiten/internal/opengl"
+	"image"
 )
 
 func newGraphicsContext(screenWidth, screenHeight, screenScale int) (*graphicsContext, error) {
@@ -72,7 +73,7 @@ func (c *graphicsContext) postUpdate() error {
 	clr := ColorMatrixI()
 	w, h := c.screen.size()
 	parts := []ImagePart{
-		{Rect{0, 0, float64(w), float64(h)}, Rect{0, 0, float64(w), float64(h)}},
+		{image.Rect(0, 0, w, h), image.Rect(0, 0, w, h)},
 	}
 	if err := c.defaultR.drawImage(c.screen, parts, geo, clr); err != nil {
 		return err
diff --git a/image.go b/image.go
index 4453ff0c1..33a870238 100644
--- a/image.go
+++ b/image.go
@@ -76,14 +76,14 @@ func v(y float64, height int) float32 {
 func textureQuads(parts []ImagePart, width, height int) []shader.TextureQuad {
 	quads := make([]shader.TextureQuad, 0, len(parts))
 	for _, part := range parts {
-		x1 := float32(part.Dst.X)
-		x2 := float32(part.Dst.X + part.Dst.Width)
-		y1 := float32(part.Dst.Y)
-		y2 := float32(part.Dst.Y + part.Dst.Height)
-		u1 := u(part.Src.X, width)
-		u2 := u(part.Src.X+part.Src.Width, width)
-		v1 := v(part.Src.Y, height)
-		v2 := v(part.Src.Y+part.Src.Height, height)
+		x1 := float32(part.Dst.Min.X)
+		x2 := float32(part.Dst.Max.X)
+		y1 := float32(part.Dst.Min.Y)
+		y2 := float32(part.Dst.Max.Y)
+		u1 := u(float64(part.Src.Min.X), width)
+		u2 := u(float64(part.Src.Max.X), width)
+		v1 := v(float64(part.Src.Min.Y), height)
+		v2 := v(float64(part.Src.Max.Y), height)
 		quad := shader.TextureQuad{x1, x2, y1, y2, u1, u2, v1, v2}
 		quads = append(quads, quad)
 	}