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[devel] Revised commentary about png_rgb_to_gray coefficents

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and fixed spelling (truely -> truly) in comments.
This commit is contained in:
Glenn Randers-Pehrson
2011-08-11 09:01:57 -05:00
parent a45ffbefb9
commit 0bc79772c8
3 changed files with 7 additions and 2 deletions
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pngrtran.c
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@@ -3093,6 +3093,11 @@ png_do_gray_to_rgb(png_row_infop row_info, png_bytep row)
*
* Y = (6968 * R + 23434 * G + 2366 * B)/32768
*
* Starting with libpng-1.5.4, if the image being converted has the
* sRGB chunk, then the sRGB numbers are used by default:
*
* Y = 0.33000*R + 0.60000*G + 0.06000*B
*
* The calculation is to be done in a linear colorspace.
*
* Other integer coefficents can be used via png_set_rgb_to_gray().