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go / go / 584e3ea2581c858688803d41e207eeaa881a2a85
commit584e3ea2581c858688803d41e207eeaa881a2a85[log] [tgz]
authorNigel Tao <nigeltao@golang.org>Thu Oct 20 16:57:55 2016 +1100
committerNigel Tao <nigeltao@golang.org>Thu Oct 20 22:27:28 2016 +0000
tree71635a63af3fd64d3f8fc7de1683714100222e00
parenta190f3c8a34b859dd578b1d30b48ecd04c7a99c7 [diff]
image/color: tweak the formula for converting to gray.

This makes grayModel and gray16Model in color.go use the exact same
formula as RGBToYCbCr in ycbcr.go. They were the same formula in theory,
but in practice the color.go versions used a divide by 1000 and the
ycbcr.go versions used a (presumably faster) shift by 16.

This implies the nice property that converting an image.RGBA to an
image.YCbCr and then taking only the Y channel is equivalent to
converting an image.RGBA directly to an image.Gray.

The difference between the two formulae is non-zero, but small:
https://play.golang.org/p/qG7oe-eqHI

Updates #16251

Change-Id: I288ecb957fd6eceb9626410bd1a8084d2e4f8198
Reviewed-on: https://go-review.googlesource.com/31538
Reviewed-by: Rob Pike <r@golang.org>
2 files changed
tree: 71635a63af3fd64d3f8fc7de1683714100222e00
  1. .github/
  2. api/
  3. doc/
  4. lib/
  5. misc/
  6. src/
  7. test/
  8. .gitattributes
  9. .gitignore
  10. AUTHORS
  11. CONTRIBUTING.md
  12. CONTRIBUTORS
  13. favicon.ico
  14. LICENSE
  15. PATENTS
  16. README.md
  17. robots.txt
README.md

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