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image/internal/imageutil: new package, used by image/draw and image/j…
…peg. The imageutil.DrawYCbCr function lives in an internal package because it is needed by both the image/draw and image/jpeg packages, but it doesn't seem right for one of those two to depend on the other. It could eventually go into the image package, but that would require committing to an API for the rest of Go 1.x. Change-Id: I7b12555c970d86409365e99eef9360702aaffa30 Reviewed-on: https://go-review.googlesource.com/7925 Reviewed-by: Brad Fitzpatrick <[email protected]> Reviewed-by: Rob Pike <[email protected]>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,96 @@ | ||
| // Copyright 2015 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 imageutil contains code shared by image-related packages. | ||
| package imageutil | ||
|
|
||
| import ( | ||
| "image" | ||
| "image/color" | ||
| ) | ||
|
|
||
| // DrawYCbCr draws the YCbCr source image on the RGBA destination image with | ||
| // r.Min in dst aligned with sp in src. It returns whether the draw was | ||
| // successful. If it returns false, no dst pixels were changed. | ||
| func DrawYCbCr(dst *image.RGBA, r image.Rectangle, src *image.YCbCr, sp image.Point) (ok bool) { | ||
| // This function exists in the image/internal/imageutil package because it | ||
| // is needed by both the image/draw and image/jpeg packages, but it doesn't | ||
| // seem right for one of those two to depend on the other. | ||
| // | ||
| // Another option is to have this code be exported in the image package, | ||
| // but we'd need to make sure we're totally happy with the API (for the | ||
| // rest of Go 1 compatibility), and decide if we want to have a more | ||
| // general purpose DrawToRGBA method for other image types. One possibility | ||
| // is: | ||
| // | ||
| // func (src *YCbCr) CopyToRGBA(dst *RGBA, dr, sr Rectangle) (effectiveDr, effectiveSr Rectangle) | ||
| // | ||
| // in the spirit of the built-in copy function for 1-dimensional slices, | ||
| // that also allowed a CopyFromRGBA method if needed. | ||
|
|
||
| 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 | ||
| } |
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