diff --git a/converter.go b/converter.go
index bab59ef..df35cea 100644
--- a/converter.go
+++ b/converter.go
@@ -41,7 +41,7 @@ func clampUint16(in int64) uint16 {
 }
 
 func resizeGeneric(in image.Image, out *image.RGBA64, scale float64, coeffs []int32, offset []int, filterLength int) {
-	oldBounds := in.Bounds()
+	oldBounds := image.Rect(0, 0, in.Bounds().Dx(), in.Bounds().Dy())
 	newBounds := out.Bounds()
 
 	for x := newBounds.Min.X; x < newBounds.Max.X; x++ {
@@ -89,7 +89,7 @@ func resizeGeneric(in image.Image, out *image.RGBA64, scale float64, coeffs []in
 }
 
 func resizeRGBA(in *image.RGBA, out *image.RGBA, scale float64, coeffs []int16, offset []int, filterLength int) {
-	oldBounds := in.Bounds()
+	oldBounds := image.Rect(0, 0, in.Rect.Dx(), in.Rect.Dy())
 	newBounds := out.Bounds()
 	minX := oldBounds.Min.X * 4
 	maxX := (oldBounds.Max.X - oldBounds.Min.X - 1) * 4
@@ -131,7 +131,7 @@ func resizeRGBA(in *image.RGBA, out *image.RGBA, scale float64, coeffs []int16,
 }
 
 func resizeRGBA64(in *image.RGBA64, out *image.RGBA64, scale float64, coeffs []int32, offset []int, filterLength int) {
-	oldBounds := in.Bounds()
+	oldBounds := image.Rect(0, 0, in.Rect.Dx(), in.Rect.Dy())
 	newBounds := out.Bounds()
 	minX := oldBounds.Min.X * 8
 	maxX := (oldBounds.Max.X - oldBounds.Min.X - 1) * 8
@@ -181,7 +181,7 @@ func resizeRGBA64(in *image.RGBA64, out *image.RGBA64, scale float64, coeffs []i
 }
 
 func resizeGray(in *image.Gray, out *image.Gray, scale float64, coeffs []int16, offset []int, filterLength int) {
-	oldBounds := in.Bounds()
+	oldBounds := image.Rect(0, 0, in.Rect.Dx(), in.Rect.Dy())
 	newBounds := out.Bounds()
 	minX := oldBounds.Min.X
 	maxX := (oldBounds.Max.X - oldBounds.Min.X - 1)
@@ -217,7 +217,7 @@ func resizeGray(in *image.Gray, out *image.Gray, scale float64, coeffs []int16,
 }
 
 func resizeGray16(in *image.Gray16, out *image.Gray16, scale float64, coeffs []int32, offset []int, filterLength int) {
-	oldBounds := in.Bounds()
+	oldBounds := image.Rect(0, 0, in.Rect.Dx(), in.Rect.Dy())
 	newBounds := out.Bounds()
 	minX := oldBounds.Min.X * 2
 	maxX := (oldBounds.Max.X - oldBounds.Min.X - 1) * 2
@@ -255,7 +255,7 @@ func resizeGray16(in *image.Gray16, out *image.Gray16, scale float64, coeffs []i
 }
 
 func resizeYCbCr(in *ycc, out *ycc, scale float64, coeffs []int16, offset []int, filterLength int) {
-	oldBounds := in.Bounds()
+	oldBounds := image.Rect(0, 0, in.Rect.Dx(), in.Rect.Dy())
 	newBounds := out.Bounds()
 	minX := oldBounds.Min.X * 3
 	maxX := (oldBounds.Max.X - oldBounds.Min.X - 1) * 3
@@ -295,7 +295,7 @@ func resizeYCbCr(in *ycc, out *ycc, scale float64, coeffs []int16, offset []int,
 }
 
 func nearestYCbCr(in *ycc, out *ycc, scale float64, coeffs []bool, offset []int, filterLength int) {
-	oldBounds := in.Bounds()
+	oldBounds := image.Rect(0, 0, in.Rect.Dx(), in.Rect.Dy())
 	newBounds := out.Bounds()
 	minX := oldBounds.Min.X * 3
 	maxX := (oldBounds.Max.X - oldBounds.Min.X - 1) * 3
diff --git a/nearest.go b/nearest.go
index 6ff22f6..69421f1 100644
--- a/nearest.go
+++ b/nearest.go
@@ -35,7 +35,7 @@ func floatToUint16(x float32) uint16 {
 }
 
 func nearestGeneric(in image.Image, out *image.RGBA64, scale float64, coeffs []bool, offset []int, filterLength int) {
-	oldBounds := in.Bounds()
+	oldBounds := image.Rect(0, 0, in.Bounds().Dx(), in.Bounds().Dy())
 	newBounds := out.Bounds()
 
 	for x := newBounds.Min.X; x < newBounds.Max.X; x++ {
@@ -82,7 +82,7 @@ func nearestGeneric(in image.Image, out *image.RGBA64, scale float64, coeffs []b
 }
 
 func nearestRGBA(in *image.RGBA, out *image.RGBA, scale float64, coeffs []bool, offset []int, filterLength int) {
-	oldBounds := in.Bounds()
+	oldBounds := image.Rect(0, 0, in.Rect.Dx(), in.Rect.Dy())
 	newBounds := out.Bounds()
 	minX := oldBounds.Min.X * 4
 	maxX := (oldBounds.Max.X - oldBounds.Min.X - 1) * 4
@@ -123,7 +123,7 @@ func nearestRGBA(in *image.RGBA, out *image.RGBA, scale float64, coeffs []bool,
 }
 
 func nearestRGBA64(in *image.RGBA64, out *image.RGBA64, scale float64, coeffs []bool, offset []int, filterLength int) {
-	oldBounds := in.Bounds()
+	oldBounds := image.Rect(0, 0, in.Rect.Dx(), in.Rect.Dy())
 	newBounds := out.Bounds()
 	minX := oldBounds.Min.X * 8
 	maxX := (oldBounds.Max.X - oldBounds.Min.X - 1) * 8
@@ -172,7 +172,7 @@ func nearestRGBA64(in *image.RGBA64, out *image.RGBA64, scale float64, coeffs []
 }
 
 func nearestGray(in *image.Gray, out *image.Gray, scale float64, coeffs []bool, offset []int, filterLength int) {
-	oldBounds := in.Bounds()
+	oldBounds := image.Rect(0, 0, in.Rect.Dx(), in.Rect.Dy())
 	newBounds := out.Bounds()
 	minX := oldBounds.Min.X
 	maxX := (oldBounds.Max.X - oldBounds.Min.X - 1)
@@ -207,7 +207,7 @@ func nearestGray(in *image.Gray, out *image.Gray, scale float64, coeffs []bool,
 }
 
 func nearestGray16(in *image.Gray16, out *image.Gray16, scale float64, coeffs []bool, offset []int, filterLength int) {
-	oldBounds := in.Bounds()
+	oldBounds := image.Rect(0, 0, in.Rect.Dx(), in.Rect.Dy())
 	newBounds := out.Bounds()
 	minX := oldBounds.Min.X * 2
 	maxX := (oldBounds.Max.X - oldBounds.Min.X - 1) * 2
diff --git a/resize_test.go b/resize_test.go
index 283b89c..41f8f46 100644
--- a/resize_test.go
+++ b/resize_test.go
@@ -3,14 +3,16 @@ package resize
 import (
 	"image"
 	"image/color"
-	"runtime"
+	"image/png"
+	"os"
+	//"runtime"
 	"testing"
 )
 
 var img = image.NewGray16(image.Rect(0, 0, 3, 3))
 
 func init() {
-	runtime.GOMAXPROCS(runtime.NumCPU())
+	//runtime.GOMAXPROCS(runtime.NumCPU())
 	img.Set(1, 1, color.White)
 }
 
@@ -64,6 +66,12 @@ func Test_SameColor(t *testing.T) {
 	}
 }
 
+func Test_Bounds(t *testing.T) {
+	img := image.NewRGBA(image.Rect(20, 10, 200, 99))
+	out := Resize(80, 80, img, Lanczos2)
+	out.At(0, 0)
+}
+
 func Benchmark_BigResizeLanczos3(b *testing.B) {
 	var m image.Image
 	for i := 0; i < b.N; i++ {
@@ -117,3 +125,21 @@ func Benchmark_LargeJpegThumbLanczos2(b *testing.B) {
 func Benchmark_LargeJpegThumbLanczos3(b *testing.B) {
 	jpegThumb(b, Lanczos3)
 }
+
+func Benchmark_LargeN(b *testing.B) {
+	file, _ := os.Open("M94A0467.png")
+	defer file.Close()
+	img, _ := png.Decode(file)
+	var output image.Image
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		output = Resize(900, 0, img, Bicubic)
+	}
+	b.StopTimer()
+
+	output.At(0, 0)
+	outPng, _ := os.Create("out.png")
+	defer outPng.Close()
+	png.Encode(outPng, output)
+}
diff --git a/ycc.go b/ycc.go
index db6ffe2..1041599 100644
--- a/ycc.go
+++ b/ycc.go
@@ -38,7 +38,7 @@ type ycc struct {
 // PixOffset returns the index of the first element of Pix that corresponds to
 // the pixel at (x, y).
 func (p *ycc) PixOffset(x, y int) int {
-	return (y * p.Stride) + (x * 3)
+	return (y-p.Rect.Min.Y)*p.Stride + (x-p.Rect.Min.X)*3
 }
 
 func (p *ycc) Bounds() image.Rectangle {
@@ -159,8 +159,9 @@ func (p *ycc) YCbCr() *image.YCbCr {
 // imageYCbCrToYCC converts a YCbCr image to a ycc image for resizing.
 func imageYCbCrToYCC(in *image.YCbCr) *ycc {
 	w, h := in.Rect.Dx(), in.Rect.Dy()
+	r := image.Rect(0, 0, w, h)
 	buf := make([]uint8, 3*w*h)
-	p := ycc{Pix: buf, Stride: 3 * w, Rect: in.Rect, SubsampleRatio: in.SubsampleRatio}
+	p := ycc{Pix: buf, Stride: 3 * w, Rect: r, SubsampleRatio: in.SubsampleRatio}
 	var off int
 
 	switch in.SubsampleRatio {
diff --git a/ycc_test.go b/ycc_test.go
index 5128173..54d53d1 100644
--- a/ycc_test.go
+++ b/ycc_test.go
@@ -18,6 +18,7 @@ package resize
 
 import (
 	"image"
+	"image/color"
 	"testing"
 )
 
@@ -119,3 +120,95 @@ func TestConvertYCbCr(t *testing.T) {
 		}
 	}
 }
+
+func TestYCbCr(t *testing.T) {
+	rects := []image.Rectangle{
+		image.Rect(0, 0, 16, 16),
+		image.Rect(1, 0, 16, 16),
+		image.Rect(0, 1, 16, 16),
+		image.Rect(1, 1, 16, 16),
+		image.Rect(1, 1, 15, 16),
+		image.Rect(1, 1, 16, 15),
+		image.Rect(1, 1, 15, 15),
+		image.Rect(2, 3, 14, 15),
+		image.Rect(7, 0, 7, 16),
+		image.Rect(0, 8, 16, 8),
+		image.Rect(0, 0, 10, 11),
+		image.Rect(5, 6, 16, 16),
+		image.Rect(7, 7, 8, 8),
+		image.Rect(7, 8, 8, 9),
+		image.Rect(8, 7, 9, 8),
+		image.Rect(8, 8, 9, 9),
+		image.Rect(7, 7, 17, 17),
+		image.Rect(8, 8, 17, 17),
+		image.Rect(9, 9, 17, 17),
+		image.Rect(10, 10, 17, 17),
+	}
+	subsampleRatios := []image.YCbCrSubsampleRatio{
+		image.YCbCrSubsampleRatio444,
+		image.YCbCrSubsampleRatio422,
+		image.YCbCrSubsampleRatio420,
+		image.YCbCrSubsampleRatio440,
+	}
+	deltas := []image.Point{
+		image.Pt(0, 0),
+		image.Pt(1000, 1001),
+		image.Pt(5001, -400),
+		image.Pt(-701, -801),
+	}
+	for _, r := range rects {
+		for _, subsampleRatio := range subsampleRatios {
+			for _, delta := range deltas {
+				testYCbCr(t, r, subsampleRatio, delta)
+			}
+		}
+		if testing.Short() {
+			break
+		}
+	}
+}
+
+func testYCbCr(t *testing.T, r image.Rectangle, subsampleRatio image.YCbCrSubsampleRatio, delta image.Point) {
+	// Create a YCbCr image m, whose bounds are r translated by (delta.X, delta.Y).
+	r1 := r.Add(delta)
+	img := image.NewYCbCr(r1, subsampleRatio)
+
+	// Initialize img's pixels. For 422 and 420 subsampling, some of the Cb and Cr elements
+	// will be set multiple times. That's OK. We just want to avoid a uniform image.
+	for y := r1.Min.Y; y < r1.Max.Y; y++ {
+		for x := r1.Min.X; x < r1.Max.X; x++ {
+			yi := img.YOffset(x, y)
+			ci := img.COffset(x, y)
+			img.Y[yi] = uint8(16*y + x)
+			img.Cb[ci] = uint8(y + 16*x)
+			img.Cr[ci] = uint8(y + 16*x)
+		}
+	}
+
+	m := imageYCbCrToYCC(img)
+
+	// Make various sub-images of m.
+	for y0 := delta.Y + 3; y0 < delta.Y+7; y0++ {
+		for y1 := delta.Y + 8; y1 < delta.Y+13; y1++ {
+			for x0 := delta.X + 3; x0 < delta.X+7; x0++ {
+				for x1 := delta.X + 8; x1 < delta.X+13; x1++ {
+					subRect := image.Rect(x0, y0, x1, y1)
+					sub := m.SubImage(subRect).(*ycc)
+
+					// For each point in the sub-image's bounds, check that m.At(x, y) equals sub.At(x, y).
+					for y := sub.Rect.Min.Y; y < sub.Rect.Max.Y; y++ {
+						for x := sub.Rect.Min.X; x < sub.Rect.Max.X; x++ {
+							color0 := m.At(x, y).(color.YCbCr)
+							color1 := sub.At(x, y).(color.YCbCr)
+							if color0 != color1 {
+								t.Errorf("r=%v, subsampleRatio=%v, delta=%v, x=%d, y=%d, color0=%v, color1=%v",
+									r, subsampleRatio, delta, x, y, color0, color1)
+								return
+							}
+						}
+					}
+				}
+			}
+		}
+	}
+}