image/gif: add more writer benchmarks

The two existing benchmarks encode randomized pixels, which isn't very
representative. The two new benchmarks encode a PNG photo as a GIF.

Also rename the benchmarks for consistency.

Also fix the bytes-per-op measure for paletted images, which are 1 (not
4) bytes per pixel.

Also simplify BenchmarkEncodeRandomPaletted (formerly just called
BenchmarkEncode). It doesn't need to generate a random palette (and the
GIF encoder largely doesn't care about the palette's RGBA values).
Use palette.Plan9 instead, a pre-existing 256-element color palette.

Change-Id: I10a6ea4e9590bb0d9f76e8cc0f4a88d43b1d650d
Reviewed-on: https://go-review.googlesource.com/c/go/+/248218
Reviewed-by: David Symonds <dsymonds@golang.org>

1 files changed, 38 insertions, 15 deletions

diff --git a/src/image/gif/writer_test.go b/src/image/gif/writer_test.go
index 9b15c8d99d..5d1b2c439e 100644
--- a/src/image/gif/writer_test.go
+++ b/src/image/gif/writer_test.go
@@ -9,6 +9,7 @@ import (
 	"image"
 	"image/color"
 	"image/color/palette"
+	"image/draw"
 	_ "image/png"
 	"io/ioutil"
 	"math/rand"
@@ -656,25 +657,14 @@ func TestEncodeWrappedImage(t *testing.T) {
 	}
 }
 
-func BenchmarkEncode(b *testing.B) {
+func BenchmarkEncodeRandomPaletted(b *testing.B) {
+	img := image.NewPaletted(image.Rect(0, 0, 640, 480), palette.Plan9)
 	rnd := rand.New(rand.NewSource(123))
-
-	// Restrict to a 256-color paletted image to avoid quantization path.
-	palette := make(color.Palette, 256)
-	for i := range palette {
-		palette[i] = color.RGBA{
-			uint8(rnd.Intn(256)),
-			uint8(rnd.Intn(256)),
-			uint8(rnd.Intn(256)),
-			255,
-		}
-	}
-	img := image.NewPaletted(image.Rect(0, 0, 640, 480), palette)
 	for i := range img.Pix {
 		img.Pix[i] = uint8(rnd.Intn(256))
 	}
 
-	b.SetBytes(640 * 480 * 4)
+	b.SetBytes(640 * 480 * 1)
 	b.ReportAllocs()
 	b.ResetTimer()
 	for i := 0; i < b.N; i++ {
@@ -682,7 +672,7 @@ func BenchmarkEncode(b *testing.B) {
 	}
 }
 
-func BenchmarkQuantizedEncode(b *testing.B) {
+func BenchmarkEncodeRandomRGBA(b *testing.B) {
 	img := image.NewRGBA(image.Rect(0, 0, 640, 480))
 	bo := img.Bounds()
 	rnd := rand.New(rand.NewSource(123))
@@ -696,6 +686,7 @@ func BenchmarkQuantizedEncode(b *testing.B) {
 			})
 		}
 	}
+
 	b.SetBytes(640 * 480 * 4)
 	b.ReportAllocs()
 	b.ResetTimer()
@@ -703,3 +694,35 @@ func BenchmarkQuantizedEncode(b *testing.B) {
 		Encode(ioutil.Discard, img, nil)
 	}
 }
+
+func BenchmarkEncodeRealisticPaletted(b *testing.B) {
+	rgba, err := readImg("../testdata/video-001.png")
+	if err != nil {
+		b.Fatalf("readImg: %v", err)
+	}
+	bo := rgba.Bounds()
+	img := image.NewPaletted(bo, palette.Plan9)
+	draw.Draw(img, bo, rgba, bo.Min, draw.Src)
+
+	b.SetBytes(int64(bo.Dx() * bo.Dy() * 1))
+	b.ReportAllocs()
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		Encode(ioutil.Discard, img, nil)
+	}
+}
+
+func BenchmarkEncodeRealisticRGBA(b *testing.B) {
+	img, err := readImg("../testdata/video-001.png")
+	if err != nil {
+		b.Fatalf("readImg: %v", err)
+	}
+	bo := img.Bounds()
+
+	b.SetBytes(int64(bo.Dx() * bo.Dy() * 4))
+	b.ReportAllocs()
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		Encode(ioutil.Discard, img, nil)
+	}
+}