From: Artyom Pervukhin Date: Sat, 21 Oct 2017 06:36:54 +0000 (+0300) Subject: image/draw: reduce drawPaletted allocations for special source cases X-Git-Tag: go1.10beta1~584 X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=088209bbe870725f82e44e604e787d7273488bd6;p=gostls13.git image/draw: reduce drawPaletted allocations for special source cases drawPaletted has to discover R,G,B,A color values of each source image pixel in a given rectangle. Doing that by calling image.Image.At() method returning color.Color interface is quite taxing allocation-wise since interface values go through heap. Introduce special cases for some concrete source types by fetching color values using type-specific methods. name old time/op new time/op delta Paletted-4 7.62ms ± 4% 3.72ms ± 3% -51.20% (p=0.008 n=5+5) name old alloc/op new alloc/op delta Paletted-4 480kB ± 0% 0kB ± 0% -99.99% (p=0.000 n=4+5) name old allocs/op new allocs/op delta Paletted-4 120k ± 0% 0k ± 0% -100.00% (p=0.008 n=5+5) Updates #15759. Change-Id: I0ce1770ff600ac80599541aaad4c2c826855c8fb Reviewed-on: https://go-review.googlesource.com/72370 Reviewed-by: Nigel Tao --- diff --git a/src/image/draw/draw.go b/src/image/draw/draw.go index a31dd427ce..f81d791f18 100644 --- a/src/image/draw/draw.go +++ b/src/image/draw/draw.go @@ -603,6 +603,18 @@ func drawPaletted(dst Image, r image.Rectangle, src image.Image, sp image.Point, quantErrorCurr = make([][4]int32, r.Dx()+2) quantErrorNext = make([][4]int32, r.Dx()+2) } + pxRGBA := func(x, y int) (r, g, b, a uint32) { return src.At(x, y).RGBA() } + // Fast paths for special cases to avoid excessive use of the color.Color + // interface which escapes to the heap but need to be discovered for + // each pixel on r. See also https://golang.org/issues/15759. + switch src0 := src.(type) { + case *image.RGBA: + pxRGBA = func(x, y int) (r, g, b, a uint32) { return src0.RGBAAt(x, y).RGBA() } + case *image.NRGBA: + pxRGBA = func(x, y int) (r, g, b, a uint32) { return src0.NRGBAAt(x, y).RGBA() } + case *image.YCbCr: + pxRGBA = func(x, y int) (r, g, b, a uint32) { return src0.YCbCrAt(x, y).RGBA() } + } // Loop over each source pixel. out := color.RGBA64{A: 0xffff} @@ -610,7 +622,7 @@ func drawPaletted(dst Image, r image.Rectangle, src image.Image, sp image.Point, for x := 0; x != r.Dx(); x++ { // er, eg and eb are the pixel's R,G,B values plus the // optional Floyd-Steinberg error. - sr, sg, sb, sa := src.At(sp.X+x, sp.Y+y).RGBA() + sr, sg, sb, sa := pxRGBA(sp.X+x, sp.Y+y) er, eg, eb, ea := int32(sr), int32(sg), int32(sb), int32(sa) if floydSteinberg { er = clamp(er + quantErrorCurr[x+1][0]/16)