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Article:
  Bitmap Image Filters
Subject:   Grayscale conversion
Date:   2002-08-07 10:32:26
From:   chieftypist
The Y = (R + G + B) / 3 is a very rough approximation for grayscale. It's better to use:


Y = (0.222*R) + (0.707*G) + (0.071*B)


or


Y' = (0.299*R) + (0.587*G) + (0.114*B)


(depending on whose standard you want to follow :-)


With the speed of today's processors, the hit for doing the floating point aritmetic is negligible.


More information about colorspace conversions can be found at:


http://www.neuro.sfc.keio.ac.jp/~aly/polygon/info/color-space-faq.html


It's pretty hairy stuff, thankfully NSColor handles most of it transparently.


BTW, I'm loving this whole series. Really good work, Mike. Looking forward to the book!


-ch


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  1. Michael Beam photo Grayscale conversion
    2002-08-08 14:06:03  Michael Beam | O'Reilly Author [View]

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