diff --git a/example/gamma/main.go b/example/gamma/main.go
index 8fe4539..652eb42 100644
--- a/example/gamma/main.go
+++ b/example/gamma/main.go
@@ -21,17 +21,6 @@ func p(x, y int) raster.Point {
 	return raster.Point{raster.Fix32(x * 256), raster.Fix32(y * 256)}
 }
 
-func clear(m *image.Alpha) {
-	b := m.Bounds()
-	for y := b.Min.Y; y < b.Max.Y; y++ {
-		base := y * m.Stride
-		p := m.Pix[base+b.Min.X : base+b.Max.X]
-		for i, _ := range p {
-			p[i] = image.AlphaColor{0}
-		}
-	}
-}
-
 func main() {
 	// Draw a rounded corner that is one pixel wide.
 	r := raster.NewRasterizer(50, 50)
@@ -57,7 +46,7 @@ func main() {
 	painter := raster.NewAlphaSrcPainter(mask)
 	gammas := []float64{1.0 / 10.0, 1.0 / 3.0, 1.0 / 2.0, 2.0 / 3.0, 4.0 / 5.0, 1.0, 5.0 / 4.0, 3.0 / 2.0, 2.0, 3.0, 10.0}
 	for i, g := range gammas {
-		clear(mask)
+		draw.Draw(mask, mask.Bounds(), image.Transparent, image.ZP, draw.Src)
 		r.Rasterize(raster.NewGammaCorrectionPainter(painter, g))
 		x, y := 50*i+25, 25
 		draw.DrawMask(rgba, image.Rect(x, y, x+50, y+50), image.White, image.ZP, mask, image.ZP, draw.Over)
diff --git a/example/round/main.go b/example/round/main.go
index e0349ee..7e87cff 100644
--- a/example/round/main.go
+++ b/example/round/main.go
@@ -14,6 +14,7 @@ import (
 	"bufio"
 	"fmt"
 	"image"
+	"image/draw"
 	"image/png"
 	"log"
 	"math"
@@ -31,12 +32,7 @@ func main() {
 	t := raster.Fix32(r * math.Tan(math.Pi/8))
 
 	m := image.NewRGBA(800, 600)
-	for y := 0; y < 600; y++ {
-		p := m.Pix[y*m.Stride : y*m.Stride+800]
-		for i := range p {
-			p[i] = image.RGBAColor{63, 63, 63, 255}
-		}
-	}
+	draw.Draw(m, m.Bounds(), &image.ColorImage{image.RGBAColor{63, 63, 63, 255}}, image.ZP, draw.Src)
 	mp := raster.NewRGBAPainter(m)
 	mp.SetColor(image.Black)
 	z := raster.NewRasterizer(800, 600)
diff --git a/freetype/raster/paint.go b/freetype/raster/paint.go
index dfe53ea..e3bc50b 100644
--- a/freetype/raster/paint.go
+++ b/freetype/raster/paint.go
@@ -58,7 +58,7 @@ func (r AlphaOverPainter) Paint(ss []Span, done bool) {
 		if s.X0 >= s.X1 {
 			continue
 		}
-		base := s.Y * r.Image.Stride
+		base := (s.Y-r.Image.Rect.Min.Y)*r.Image.Stride - r.Image.Rect.Min.X
 		p := r.Image.Pix[base+s.X0 : base+s.X1]
 		a := int(s.A >> 24)
 		for i, c := range p {
@@ -99,7 +99,7 @@ func (r AlphaSrcPainter) Paint(ss []Span, done bool) {
 		if s.X0 >= s.X1 {
 			continue
 		}
-		base := s.Y * r.Image.Stride
+		base := (s.Y-r.Image.Rect.Min.Y)*r.Image.Stride - r.Image.Rect.Min.X
 		p := r.Image.Pix[base+s.X0 : base+s.X1]
 		color := image.AlphaColor{uint8(s.A >> 24)}
 		for i := range p {
@@ -141,7 +141,7 @@ func (r *RGBAPainter) Paint(ss []Span, done bool) {
 		if s.X0 >= s.X1 {
 			continue
 		}
-		base := s.Y * r.Image.Stride
+		base := (s.Y-r.Image.Rect.Min.Y)*r.Image.Stride - r.Image.Rect.Min.X
 		p := r.Image.Pix[base+s.X0 : base+s.X1]
 		for i, rgba := range p {
 			// This code is duplicated from drawGlyphOver in $GOROOT/src/pkg/exp/draw/draw.go.