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image/jpeg: remove the (temporary) dependency on image/draw.

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Change-Id: Idd66f9c3c9eaa4ff1f950fb90e4800dc625dec08
Reviewed-on: https://go-review.googlesource.com/4916
Reviewed-by: Alex Brainman <alex.brainman@gmail.com>
This commit is contained in:
Nigel Tao 2015-02-16 15:10:50 +11:00
parent 7b36227002
commit 10a4696fb8
2 changed files with 79 additions and 5 deletions
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2
src/image/draw/draw.go
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@ -392,6 +392,8 @@ func drawNRGBASrc(dst *image.RGBA, r image.Rectangle, src *image.NRGBA, sp image
}
}
// TODO(nigeltao): this function is copy/pasted to image/jpeg/reader.go. We
// should un-copy/paste it.
func drawYCbCr(dst *image.RGBA, r image.Rectangle, src *image.YCbCr, sp image.Point) (ok bool) {
// An image.YCbCr is always fully opaque, and so if the mask is implicitly nil
// (i.e. fully opaque) then the op is effectively always Src.

82
src/image/jpeg/reader.go
View File

@ -10,7 +10,6 @@ package jpeg
import (
"image"
"image/color"
"image/draw"
"io"
)
@ -587,10 +586,7 @@ func (d *decoder) applyBlack() (image.Image, error) {
// above, so in practice, only the fourth channel (black) is inverted.
bounds := d.img3.Bounds()
img := image.NewRGBA(bounds)
// TODO(nigeltao): do the draw.Draw YCbCr -> RGB conversion directly,
// instead of having the image/jpeg package depend on the image/draw
// package.
draw.Draw(img, bounds, d.img3, bounds.Min, draw.Src)
drawYCbCr(img, bounds, d.img3, bounds.Min)
for iBase, y := 0, bounds.Min.Y; y < bounds.Max.Y; iBase, y = iBase+img.Stride, y+1 {
for i, x := iBase+3, bounds.Min.X; x < bounds.Max.X; i, x = i+4, x+1 {
img.Pix[i] = 255 - d.blackPix[(y-bounds.Min.Y)*d.blackStride+(x-bounds.Min.X)]
@ -639,6 +635,82 @@ func (d *decoder) applyBlack() (image.Image, error) {
return img, nil
}
// drawYCbCr is the non-exported drawYCbCr function copy/pasted from the
// image/draw package. It is copy/pasted because it doesn't seem right for the
// image/jpeg package to depend on image/draw.
//
// TODO(nigeltao): remove the copy/paste, possibly by moving this to be an
// exported method on *image.YCbCr. We'd need to make sure we're totally happy
// with the API (for the rest of Go 1 compatibility) though, and if we want to
// have a more general purpose DrawToRGBA method for other image types.
func drawYCbCr(dst *image.RGBA, r image.Rectangle, src *image.YCbCr, sp image.Point) (ok bool) {
// An image.YCbCr is always fully opaque, and so if the mask is implicitly nil
// (i.e. fully opaque) then the op is effectively always Src.
x0 := (r.Min.X - dst.Rect.Min.X) * 4
x1 := (r.Max.X - dst.Rect.Min.X) * 4
y0 := r.Min.Y - dst.Rect.Min.Y
y1 := r.Max.Y - dst.Rect.Min.Y
switch src.SubsampleRatio {
case image.YCbCrSubsampleRatio444:
for y, sy := y0, sp.Y; y != y1; y, sy = y+1, sy+1 {
dpix := dst.Pix[y*dst.Stride:]
yi := (sy-src.Rect.Min.Y)*src.YStride + (sp.X - src.Rect.Min.X)
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
dpix[x+3] = 255
}
}
case image.YCbCrSubsampleRatio422:
for y, sy := y0, sp.Y; y != y1; y, sy = y+1, sy+1 {
dpix := dst.Pix[y*dst.Stride:]
yi := (sy-src.Rect.Min.Y)*src.YStride + (sp.X - src.Rect.Min.X)
ciBase := (sy-src.Rect.Min.Y)*src.CStride - src.Rect.Min.X/2
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
dpix[x+3] = 255
}
}
case image.YCbCrSubsampleRatio420:
for y, sy := y0, sp.Y; y != y1; y, sy = y+1, sy+1 {
dpix := dst.Pix[y*dst.Stride:]
yi := (sy-src.Rect.Min.Y)*src.YStride + (sp.X - src.Rect.Min.X)
ciBase := (sy/2-src.Rect.Min.Y/2)*src.CStride - src.Rect.Min.X/2
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
dpix[x+3] = 255
}
}
case image.YCbCrSubsampleRatio440:
for y, sy := y0, sp.Y; y != y1; y, sy = y+1, sy+1 {
dpix := dst.Pix[y*dst.Stride:]
yi := (sy-src.Rect.Min.Y)*src.YStride + (sp.X - src.Rect.Min.X)
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
dpix[x+3] = 255
}
}
default:
return false
}
return true
}
// Decode reads a JPEG image from r and returns it as an image.Image.
func Decode(r io.Reader) (image.Image, error) {
var d decoder