From 807ce2719c243f6d8640de774599e3335883eacb Mon Sep 17 00:00:00 2001 From: Brad Fitzpatrick Date: Mon, 2 May 2011 07:26:40 -0700 Subject: [PATCH] jpeg: speed up RGBA encoding ~%50 Avoids image.At(), color.RGBA(), opposing 8 bit shifts, and min function calls in a loop. Not as pretty as before, but the pure version is still there to revert back to later if/when the compiler gets better. before (best of 5) jpeg.BenchmarkEncodeRGBOpaque 50 64781360 ns/op 18.97 MB/s after (best of 5) jpeg.BenchmarkEncodeRGBOpaque 50 42044300 ns/op 29.23 MB/s (benchmarked on an HP z600; 16 core Xeon E5520 @ 2.27Ghz) R=r, r2, nigeltao CC=golang-dev https://golang.org/cl/4433088 --- src/pkg/image/jpeg/writer.go | 32 +++++++++++++++++++++++++++++++- 1 file changed, 31 insertions(+), 1 deletion(-) diff --git a/src/pkg/image/jpeg/writer.go b/src/pkg/image/jpeg/writer.go index 505cce04fb..52b3dc4e2c 100644 --- a/src/pkg/image/jpeg/writer.go +++ b/src/pkg/image/jpeg/writer.go @@ -391,6 +391,31 @@ func toYCbCr(m image.Image, p image.Point, yBlock, cbBlock, crBlock *block) { } } +// rgbaToYCbCr is a specialized version of toYCbCr for image.RGBA images. +func rgbaToYCbCr(m *image.RGBA, p image.Point, yBlock, cbBlock, crBlock *block) { + b := m.Bounds() + xmax := b.Max.X - 1 + ymax := b.Max.Y - 1 + for j := 0; j < 8; j++ { + sj := p.Y + j + if sj > ymax { + sj = ymax + } + yoff := sj * m.Stride + for i := 0; i < 8; i++ { + sx := p.X + i + if sx > xmax { + sx = xmax + } + col := &m.Pix[yoff+sx] + yy, cb, cr := ycbcr.RGBToYCbCr(col.R, col.G, col.B) + yBlock[8*j+i] = int(yy) + cbBlock[8*j+i] = int(cb) + crBlock[8*j+i] = int(cr) + } + } +} + // scale scales the 16x16 region represented by the 4 src blocks to the 8x8 // dst block. func scale(dst *block, src *[4]block) { @@ -431,13 +456,18 @@ func (e *encoder) writeSOS(m image.Image) { prevDCY, prevDCCb, prevDCCr int ) bounds := m.Bounds() + rgba, _ := m.(*image.RGBA) for y := bounds.Min.Y; y < bounds.Max.Y; y += 16 { for x := bounds.Min.X; x < bounds.Max.X; x += 16 { for i := 0; i < 4; i++ { xOff := (i & 1) * 8 yOff := (i & 2) * 4 p := image.Point{x + xOff, y + yOff} - toYCbCr(m, p, &yBlock, &cbBlock[i], &crBlock[i]) + if rgba != nil { + rgbaToYCbCr(rgba, p, &yBlock, &cbBlock[i], &crBlock[i]) + } else { + toYCbCr(m, p, &yBlock, &cbBlock[i], &crBlock[i]) + } prevDCY = e.writeBlock(&yBlock, 0, prevDCY) } scale(&cBlock, &cbBlock) -- 2.48.1