PixelPacket Lab values

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PixelPacket Lab values

Post by citydavid » 2014-01-08T05:56:30-07:00

How Lab values are stored? I read that in the last version ImageMagick-6.8.8-Q16, the a* value and b* value are unsigned, but I don't find a correct correlation!

For example: in a tiff image with lab colorspace I have L=50 a=-10 b =-10, and pixel->red =34504 pixel->green =28257pixel->blue =30184.

What I do wrong?!


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Re: PixelPacket Lab values

Post by fmw42 » 2014-01-08T11:19:39-07:00

The values are biased so that they can be represented as non-negative integers (for non-hdri compile). I believe that in HDRI compile, they are not biased. You will need to look at the code to see how that is done.

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