image/internal/imageutil: inline the color.YCbCrToRGB calls.

The image/draw benchmark:
benchmark          old ns/op     new ns/op     delta
BenchmarkYCbCr     1198605       978647        -18.35%

Change-Id: Iacfc21e6f641ecb05adc00b3aec0048f1f43d265
Reviewed-on: https://go-review.googlesource.com/7952
Reviewed-by: Rob Pike <r@golang.org>

diff --git a/src/image/internal/imageutil/gen.go b/src/image/internal/imageutil/gen.go
index 59125dadbf860460be93d19cd14d2cd3af119d46..cde05ad088b444f065454d2b8a2a2f2037ff02ee 100644 (file)
--- a/src/image/internal/imageutil/gen.go
+++ b/src/image/internal/imageutil/gen.go
@@ -47,7 +47,6 @@ package imageutil
 
 import (
        "image"
-       "image/color"
 )
 
 // DrawYCbCr draws the YCbCr source image on the RGBA destination image with
@@ -94,10 +93,33 @@ const sratioCase = `
                        dpix := dst.Pix[y*dst.Stride:]
                        yi := (sy-src.Rect.Min.Y)*src.YStride + (sp.X - src.Rect.Min.X)
                        %s
-                               rr, gg, bb := color.YCbCrToRGB(src.Y[yi], src.Cb[ci], src.Cr[ci])
-                               dpix[x+0] = rr
-                               dpix[x+1] = gg
-                               dpix[x+2] = bb
+
+                               // This is an inline version of image/color/ycbcr.go's func YCbCrToRGB.
+                               yy1 := int(src.Y[yi])<<16 + 1<<15
+                               cb1 := int(src.Cb[ci]) - 128
+                               cr1 := int(src.Cr[ci]) - 128
+                               r := (yy1 + 91881*cr1) >> 16
+                               g := (yy1 - 22554*cb1 - 46802*cr1) >> 16
+                               b := (yy1 + 116130*cb1) >> 16
+                               if r < 0 {
+                                       r = 0
+                               } else if r > 255 {
+                                       r = 255
+                               }
+                               if g < 0 {
+                                       g = 0
+                               } else if g > 255 {
+                                       g = 255
+                               }
+                               if b < 0 {
+                                       b = 0
+                               } else if b > 255 {
+                                       b = 255
+                               }
+
+                               dpix[x+0] = uint8(r)
+                               dpix[x+1] = uint8(g)
+                               dpix[x+2] = uint8(b)
                                dpix[x+3] = 255
                        }
                }

diff --git a/src/image/internal/imageutil/impl.go b/src/image/internal/imageutil/impl.go
index 5a156e40bcb29368d64ef5c8030ce3b03cf3a848..d4bd3250fdfaf19b8c5b38b463fcf4457c0963ae 100644 (file)
--- a/src/image/internal/imageutil/impl.go
+++ b/src/image/internal/imageutil/impl.go
@@ -4,7 +4,6 @@ package imageutil
 
 import (
        "image"
-       "image/color"
 )
 
 // DrawYCbCr draws the YCbCr source image on the RGBA destination image with
@@ -44,10 +43,32 @@ func DrawYCbCr(dst *image.RGBA, r image.Rectangle, src *image.YCbCr, sp image.Po
                        ci := (sy-src.Rect.Min.Y)*src.CStride + (sp.X - src.Rect.Min.X)
                        for x := x0; x != x1; x, yi, ci = x+4, yi+1, ci+1 {
 
-                               rr, gg, bb := color.YCbCrToRGB(src.Y[yi], src.Cb[ci], src.Cr[ci])
-                               dpix[x+0] = rr
-                               dpix[x+1] = gg
-                               dpix[x+2] = bb
+                               // This is an inline version of image/color/ycbcr.go's func YCbCrToRGB.
+                               yy1 := int(src.Y[yi])<<16 + 1<<15
+                               cb1 := int(src.Cb[ci]) - 128
+                               cr1 := int(src.Cr[ci]) - 128
+                               r := (yy1 + 91881*cr1) >> 16
+                               g := (yy1 - 22554*cb1 - 46802*cr1) >> 16
+                               b := (yy1 + 116130*cb1) >> 16
+                               if r < 0 {
+                                       r = 0
+                               } else if r > 255 {
+                                       r = 255
+                               }
+                               if g < 0 {
+                                       g = 0
+                               } else if g > 255 {
+                                       g = 255
+                               }
+                               if b < 0 {
+                                       b = 0
+                               } else if b > 255 {
+                                       b = 255
+                               }
+
+                               dpix[x+0] = uint8(r)
+                               dpix[x+1] = uint8(g)
+                               dpix[x+2] = uint8(b)
                                dpix[x+3] = 255
                        }
                }
@@ -61,10 +82,32 @@ func DrawYCbCr(dst *image.RGBA, r image.Rectangle, src *image.YCbCr, sp image.Po
                        for x, sx := x0, sp.X; x != x1; x, sx, yi = x+4, sx+1, yi+1 {
                                ci := ciBase + sx/2
 
-                               rr, gg, bb := color.YCbCrToRGB(src.Y[yi], src.Cb[ci], src.Cr[ci])
-                               dpix[x+0] = rr
-                               dpix[x+1] = gg
-                               dpix[x+2] = bb
+                               // This is an inline version of image/color/ycbcr.go's func YCbCrToRGB.
+                               yy1 := int(src.Y[yi])<<16 + 1<<15
+                               cb1 := int(src.Cb[ci]) - 128
+                               cr1 := int(src.Cr[ci]) - 128
+                               r := (yy1 + 91881*cr1) >> 16
+                               g := (yy1 - 22554*cb1 - 46802*cr1) >> 16
+                               b := (yy1 + 116130*cb1) >> 16
+                               if r < 0 {
+                                       r = 0
+                               } else if r > 255 {
+                                       r = 255
+                               }
+                               if g < 0 {
+                                       g = 0
+                               } else if g > 255 {
+                                       g = 255
+                               }
+                               if b < 0 {
+                                       b = 0
+                               } else if b > 255 {
+                                       b = 255
+                               }
+
+                               dpix[x+0] = uint8(r)
+                               dpix[x+1] = uint8(g)
+                               dpix[x+2] = uint8(b)
                                dpix[x+3] = 255
                        }
                }
@@ -78,10 +121,32 @@ func DrawYCbCr(dst *image.RGBA, r image.Rectangle, src *image.YCbCr, sp image.Po
                        for x, sx := x0, sp.X; x != x1; x, sx, yi = x+4, sx+1, yi+1 {
                                ci := ciBase + sx/2
 
-                               rr, gg, bb := color.YCbCrToRGB(src.Y[yi], src.Cb[ci], src.Cr[ci])
-                               dpix[x+0] = rr
-                               dpix[x+1] = gg
-                               dpix[x+2] = bb
+                               // This is an inline version of image/color/ycbcr.go's func YCbCrToRGB.
+                               yy1 := int(src.Y[yi])<<16 + 1<<15
+                               cb1 := int(src.Cb[ci]) - 128
+                               cr1 := int(src.Cr[ci]) - 128
+                               r := (yy1 + 91881*cr1) >> 16
+                               g := (yy1 - 22554*cb1 - 46802*cr1) >> 16
+                               b := (yy1 + 116130*cb1) >> 16
+                               if r < 0 {
+                                       r = 0
+                               } else if r > 255 {
+                                       r = 255
+                               }
+                               if g < 0 {
+                                       g = 0
+                               } else if g > 255 {
+                                       g = 255
+                               }
+                               if b < 0 {
+                                       b = 0
+                               } else if b > 255 {
+                                       b = 255
+                               }
+
+                               dpix[x+0] = uint8(r)
+                               dpix[x+1] = uint8(g)
+                               dpix[x+2] = uint8(b)
                                dpix[x+3] = 255
                        }
                }
@@ -94,10 +159,32 @@ func DrawYCbCr(dst *image.RGBA, r image.Rectangle, src *image.YCbCr, sp image.Po
                        ci := (sy/2-src.Rect.Min.Y/2)*src.CStride + (sp.X - src.Rect.Min.X)
                        for x := x0; x != x1; x, yi, ci = x+4, yi+1, ci+1 {
 
-                               rr, gg, bb := color.YCbCrToRGB(src.Y[yi], src.Cb[ci], src.Cr[ci])
-                               dpix[x+0] = rr
-                               dpix[x+1] = gg
-                               dpix[x+2] = bb
+                               // This is an inline version of image/color/ycbcr.go's func YCbCrToRGB.
+                               yy1 := int(src.Y[yi])<<16 + 1<<15
+                               cb1 := int(src.Cb[ci]) - 128
+                               cr1 := int(src.Cr[ci]) - 128
+                               r := (yy1 + 91881*cr1) >> 16
+                               g := (yy1 - 22554*cb1 - 46802*cr1) >> 16
+                               b := (yy1 + 116130*cb1) >> 16
+                               if r < 0 {
+                                       r = 0
+                               } else if r > 255 {
+                                       r = 255
+                               }
+                               if g < 0 {
+                                       g = 0
+                               } else if g > 255 {
+                                       g = 255
+                               }
+                               if b < 0 {
+                                       b = 0
+                               } else if b > 255 {
+                                       b = 255
+                               }
+
+                               dpix[x+0] = uint8(r)
+                               dpix[x+1] = uint8(g)
+                               dpix[x+2] = uint8(b)
                                dpix[x+3] = 255
                        }
                }