draw: test that the fast path implementations match the generic ones.
Change-Id: I34418bd8e5dec7b03e9c29efdab10f6116b4463f
Reviewed-on: https://go-review.googlesource.com/5730
Reviewed-by: Rob Pike <r@golang.org>
diff --git a/draw/scale_test.go b/draw/scale_test.go
index 6d4baac..0404d8e 100644
--- a/draw/scale_test.go
+++ b/draw/scale_test.go
@@ -5,10 +5,13 @@
package draw
import (
+ "bytes"
"flag"
"fmt"
"image"
+ "image/color"
"image/png"
+ "math/rand"
"os"
"reflect"
"testing"
@@ -81,33 +84,123 @@
func TestScaleDown(t *testing.T) { testScale(t, 100, 100, "down", "280x360.jpeg") }
func TestScaleUp(t *testing.T) { testScale(t, 75, 100, "up", "14x18.png") }
-// TODO: test that scaling concrete types like *image.RGBA and *image.YCbCr
-// give the same results as scaling those images wrapped in another Image or
-// image.Image type that would skip the fast-path type switch.
+// The fooWrapper types wrap the dst or src image to avoid triggering the
+// type-specific fast path implementations.
+type (
+ dstWrapper struct{ Image }
+ srcWrapper struct{ image.Image }
+)
-func srcNRGBA() (image.Image, error) {
- return image.NewNRGBA(image.Rect(0, 0, 1024, 768)), nil
+// TestFastPaths tests that the fast path implementations produce identical
+// results to the generic implementation.
+func TestFastPaths(t *testing.T) {
+ drs := []image.Rectangle{
+ image.Rect(0, 0, 10, 10), // The dst bounds.
+ image.Rect(3, 4, 8, 6), // A strict subset of the dst bounds.
+ image.Rect(-3, -5, 2, 4), // Partial out-of-bounds #0.
+ image.Rect(4, -2, 6, 12), // Partial out-of-bounds #1.
+ image.Rect(12, 14, 23, 45), // Complete out-of-bounds.
+ image.Rect(5, 5, 5, 5), // Empty.
+ }
+ srs := []image.Rectangle{
+ image.Rect(0, 0, 12, 9), // The src bounds.
+ image.Rect(2, 2, 10, 8), // A strict subset of the src bounds.
+ image.Rect(10, 5, 20, 20), // Partial out-of-bounds #0.
+ image.Rect(-40, 0, 40, 8), // Partial out-of-bounds #1.
+ image.Rect(-8, -8, -4, -4), // Complete out-of-bounds.
+ image.Rect(5, 5, 5, 5), // Empty.
+ }
+ srcfs := []func(image.Rectangle) (image.Image, error){
+ srcNRGBA,
+ srcRGBA,
+ srcUniform,
+ srcYCbCr,
+ }
+ var srcs []image.Image
+ for _, srcf := range srcfs {
+ src, err := srcf(srs[0])
+ if err != nil {
+ t.Fatal(err)
+ }
+ srcs = append(srcs, src)
+ }
+ qs := []Interpolator{
+ NearestNeighbor,
+ ApproxBiLinear,
+ CatmullRom,
+ }
+ blue := image.NewUniform(color.RGBA{0x11, 0x22, 0x44, 0x7f})
+
+ for _, dr := range drs {
+ for _, src := range srcs {
+ for _, sr := range srs {
+ for _, q := range qs {
+ dst0 := image.NewRGBA(drs[0])
+ dst1 := image.NewRGBA(drs[0])
+ Draw(dst0, dst0.Bounds(), blue, image.Point{}, Src)
+ Draw(dstWrapper{dst1}, dst1.Bounds(), srcWrapper{blue}, image.Point{}, Src)
+ Scale(dst0, dr, src, sr, q)
+ Scale(dstWrapper{dst1}, dr, srcWrapper{src}, sr, q)
+ if !bytes.Equal(dst0.Pix, dst1.Pix) {
+ t.Errorf("pix differ for dr=%v, src=%T, sr=%v, q=%T", dr, src, sr, q)
+ }
+ }
+ }
+ }
+ }
}
-func srcRGBA() (image.Image, error) {
- return image.NewRGBA(image.Rect(0, 0, 1024, 768)), nil
+func srcNRGBA(boundsHint image.Rectangle) (image.Image, error) {
+ m := image.NewNRGBA(boundsHint)
+ r := rand.New(rand.NewSource(1))
+ for i := range m.Pix {
+ m.Pix[i] = uint8(r.Intn(256))
+ }
+ return m, nil
}
-func srcUniform() (image.Image, error) {
- return image.White, nil
+func srcRGBA(boundsHint image.Rectangle) (image.Image, error) {
+ m := image.NewRGBA(boundsHint)
+ r := rand.New(rand.NewSource(2))
+ for i := range m.Pix {
+ m.Pix[i] = uint8(r.Intn(256))
+ }
+ // RGBA is alpha-premultiplied, so the R, G and B values should
+ // be <= the A values.
+ for i := 0; i < len(m.Pix); i += 4 {
+ m.Pix[i+0] = uint8(uint32(m.Pix[i+0]) * uint32(m.Pix[i+3]) / 0xff)
+ m.Pix[i+1] = uint8(uint32(m.Pix[i+1]) * uint32(m.Pix[i+3]) / 0xff)
+ m.Pix[i+2] = uint8(uint32(m.Pix[i+2]) * uint32(m.Pix[i+3]) / 0xff)
+ }
+ return m, nil
}
-func srcYCbCr() (image.Image, error) {
- return image.NewYCbCr(image.Rect(0, 0, 1024, 768), image.YCbCrSubsampleRatio420), nil
+func srcUniform(boundsHint image.Rectangle) (image.Image, error) {
+ return image.NewUniform(color.RGBA64{0x1234, 0x5555, 0x9181, 0xbeef}), nil
}
-func srcYCbCrLarge() (image.Image, error) {
+func srcYCbCr(boundsHint image.Rectangle) (image.Image, error) {
+ m := image.NewYCbCr(boundsHint, image.YCbCrSubsampleRatio420)
+ r := rand.New(rand.NewSource(3))
+ for i := range m.Y {
+ m.Y[i] = uint8(r.Intn(256))
+ }
+ for i := range m.Cb {
+ m.Cb[i] = uint8(r.Intn(256))
+ }
+ for i := range m.Cr {
+ m.Cr[i] = uint8(r.Intn(256))
+ }
+ return m, nil
+}
+
+func srcYCbCrLarge(boundsHint image.Rectangle) (image.Image, error) {
// 3072 x 2304 is over 7 million pixels at 4:3, comparable to a
// 2015 smart-phone camera's output.
- return image.NewYCbCr(image.Rect(0, 0, 3072, 2304), image.YCbCrSubsampleRatio420), nil
+ return srcYCbCr(image.Rect(0, 0, 3072, 2304))
}
-func srcTux() (image.Image, error) {
+func srcTux(boundsHint image.Rectangle) (image.Image, error) {
// tux.png is a 386 x 395 image.
f, err := os.Open("../testdata/tux.png")
if err != nil {
@@ -121,9 +214,9 @@
return src, nil
}
-func benchScale(b *testing.B, srcf func() (image.Image, error), w int, h int, q Interpolator) {
+func benchScale(b *testing.B, srcf func(image.Rectangle) (image.Image, error), w int, h int, q Interpolator) {
dst := image.NewRGBA(image.Rect(0, 0, w, h))
- src, err := srcf()
+ src, err := srcf(image.Rect(0, 0, 1024, 768))
if err != nil {
b.Fatal(err)
}
