image/draw: add benchmarks.

R=r
CC=golang-dev
https://golang.org/cl/4695043

src/pkg/image/draw/bench_test.go

+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package draw
+
+import (
+	"image"
+	"image/ycbcr"
+	"testing"
+)
+
+const (
+	dstw, dsth = 640, 480
+	srcw, srch = 400, 300
+)
+
+// bench benchmarks drawing src and mask images onto a dst image with the
+// given op and the color models to create those images from.
+// The created images' pixels are initialized to non-zero values.
+func bench(b *testing.B, dcm, scm, mcm image.ColorModel, op Op) {
+	b.StopTimer()
+
+	var dst Image
+	switch dcm {
+	case image.RGBAColorModel:
+		dst1 := image.NewRGBA(dstw, dsth)
+		for y := 0; y < dsth; y++ {
+			for x := 0; x < dstw; x++ {
+				dst1.SetRGBA(x, y, image.RGBAColor{
+					uint8(5 * x % 0x100),
+					uint8(7 * y % 0x100),
+					uint8((7*x + 5*y) % 0x100),
+					0xff,
+				})
+			}
+		}
+		dst = dst1
+	case image.RGBA64ColorModel:
+		dst1 := image.NewRGBA64(dstw, dsth)
+		for y := 0; y < dsth; y++ {
+			for x := 0; x < dstw; x++ {
+				dst1.SetRGBA64(x, y, image.RGBA64Color{
+					uint16(53 * x % 0x10000),
+					uint16(59 * y % 0x10000),
+					uint16((59*x + 53*y) % 0x10000),
+					0xffff,
+				})
+			}
+		}
+		dst = dst1
+	default:
+		panic("unreachable")
+	}
+
+	var src image.Image
+	switch scm {
+	case nil:
+		src = &image.ColorImage{image.RGBAColor{0x11, 0x22, 0x33, 0xff}}
+	case image.RGBAColorModel:
+		src1 := image.NewRGBA(srcw, srch)
+		for y := 0; y < srch; y++ {
+			for x := 0; x < srcw; x++ {
+				src1.SetRGBA(x, y, image.RGBAColor{
+					uint8(13 * x % 0x80),
+					uint8(11 * y % 0x80),
+					uint8((11*x + 13*y) % 0x80),
+					0x7f,
+				})
+			}
+		}
+		src = src1
+	case image.RGBA64ColorModel:
+		src1 := image.NewRGBA64(srcw, srch)
+		for y := 0; y < srch; y++ {
+			for x := 0; x < srcw; x++ {
+				src1.SetRGBA64(x, y, image.RGBA64Color{
+					uint16(103 * x % 0x8000),
+					uint16(101 * y % 0x8000),
+					uint16((101*x + 103*y) % 0x8000),
+					0x7fff,
+				})
+			}
+		}
+		src = src1
+	case image.NRGBAColorModel:
+		src1 := image.NewNRGBA(srcw, srch)
+		for y := 0; y < srch; y++ {
+			for x := 0; x < srcw; x++ {
+				src1.SetNRGBA(x, y, image.NRGBAColor{
+					uint8(13 * x % 0x100),
+					uint8(11 * y % 0x100),
+					uint8((11*x + 13*y) % 0x100),
+					0x7f,
+				})
+			}
+		}
+		src = src1
+	case ycbcr.YCbCrColorModel:
+		yy := make([]uint8, srcw*srch)
+		cb := make([]uint8, srcw*srch)
+		cr := make([]uint8, srcw*srch)
+		for i := range yy {
+			yy[i] = uint8(3 * i % 0x100)
+			cb[i] = uint8(5 * i % 0x100)
+			cr[i] = uint8(7 * i % 0x100)
+		}
+		src = &ycbcr.YCbCr{
+			Y:              yy,
+			Cb:             cb,
+			Cr:             cr,
+			YStride:        srcw,
+			CStride:        srcw,
+			SubsampleRatio: ycbcr.SubsampleRatio444,
+			Rect:           image.Rect(0, 0, srcw, srch),
+		}
+	default:
+		panic("unreachable")
+	}
+
+	var mask image.Image
+	switch mcm {
+	case nil:
+		// No-op.
+	case image.AlphaColorModel:
+		mask1 := image.NewAlpha(srcw, srch)
+		for y := 0; y < srch; y++ {
+			for x := 0; x < srcw; x++ {
+				a := uint8((23*x + 29*y) % 0x100)
+				// Glyph masks are typically mostly zero,
+				// so we only set a quarter of mask1's pixels.
+				if a >= 0xc0 {
+					mask1.SetAlpha(x, y, image.AlphaColor{a})
+				}
+			}
+		}
+		mask = mask1
+	default:
+		panic("unreachable")
+	}
+
+	b.StartTimer()
+	for i := 0; i < b.N; i++ {
+		// Scatter the destination rectangle to draw into.
+		x := 3 * i % (dstw - srcw)
+		y := 7 * i % (dsth - srch)
+
+		DrawMask(dst, dst.Bounds().Add(image.Point{x, y}), src, image.ZP, mask, image.ZP, op)
+	}
+}
+
+// The BenchmarkFoo functions exercise a drawFoo fast-path function in draw.go.
+
+func BenchmarkFillOver(b *testing.B) {
+	bench(b, image.RGBAColorModel, nil, nil, Over)
+}
+
+func BenchmarkFillSrc(b *testing.B) {
+	bench(b, image.RGBAColorModel, nil, nil, Src)
+}
+
+func BenchmarkCopyOver(b *testing.B) {
+	bench(b, image.RGBAColorModel, image.RGBAColorModel, nil, Over)
+}
+
+func BenchmarkCopySrc(b *testing.B) {
+	bench(b, image.RGBAColorModel, image.RGBAColorModel, nil, Src)
+}
+
+func BenchmarkNRGBAOver(b *testing.B) {
+	bench(b, image.RGBAColorModel, image.NRGBAColorModel, nil, Over)
+}
+
+func BenchmarkNRGBASrc(b *testing.B) {
+	bench(b, image.RGBAColorModel, image.NRGBAColorModel, nil, Src)
+}
+
+func BenchmarkYCbCr(b *testing.B) {
+	bench(b, image.RGBAColorModel, ycbcr.YCbCrColorModel, nil, Over)
+}
+
+func BenchmarkGlyphOver(b *testing.B) {
+	bench(b, image.RGBAColorModel, nil, image.AlphaColorModel, Over)
+}
+
+func BenchmarkRGBA(b *testing.B) {
+	bench(b, image.RGBAColorModel, image.RGBA64ColorModel, nil, Src)
+}
+
+// The BenchmarkGenericFoo functions exercise the generic, slow-path code.
+
+func BenchmarkGenericOver(b *testing.B) {
+	bench(b, image.RGBA64ColorModel, image.RGBA64ColorModel, nil, Over)
+}
+
+func BenchmarkGenericMaskOver(b *testing.B) {
+	bench(b, image.RGBA64ColorModel, image.RGBA64ColorModel, image.AlphaColorModel, Over)
+}
+
+func BenchmarkGenericSrc(b *testing.B) {
+	bench(b, image.RGBA64ColorModel, image.RGBA64ColorModel, nil, Src)
+}
+
+func BenchmarkGenericMaskSrc(b *testing.B) {
+	bench(b, image.RGBA64ColorModel, image.RGBA64ColorModel, image.AlphaColorModel, Src)
+}