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Based on the PNGsuite.

The following set shows the use of some ancillary chunks. The left-most two contain histogram info and the right-most two chromaticity info. The chromaticity chunk defines the rgb and whitepoint coordinates according to the 1931 CIE Committee XYZ color space. The top row is the reference snapshot and the bottom row should look identical. If it does not, your software is not handling one or more of these chunks correctly.

PNGCH-CC.mng

The following images were used (left to right):

ch2n3p08 - histogram 256 colors
ch1n3p04 - histogram 15 colors
ccwn3p08 - chroma chunk w:0.3127,0.3290 r:0.64,0.33 g:0.30,0.60 b:0.15,0.06
ccwn2c08 - chroma chunk w:0.3127,0.3290 r:0.64,0.33 g:0.30,0.60 b:0.15,0.06

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