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December 2002
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2002.12.17 21:47 "CMYK JPEG's", by Dominic Smith
Sorry that this is a libjpeg question, nothing to do with TIFF - but I know there are experts here and I don't know of a libjpeg mail list. I have some CMYK JPEG (.jpg, not TIFF JPEG) files which open ok in several recent PC packages (Paintshop 7 etc). But when I read them with libjpeg they are negative. I read that JPEG doesn't define the polarity of CMYK data, and that both interpretations (black is zero and white is zero) exist in the wild. Does libjpeg use white is zero? Also, has black is zero become the de facto (de Adobe?) standard? Should I invert the libjpeg output as a matter of course, and will this cover most/virtually all images I am likely to meet? TIA Dom