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Thread: writing CMYK-Files from QImage

  1. #1
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    Default writing CMYK-Files from QImage

    Good Morning,

    i search a way to write CMYK - Pictures (z.B. tiff).

    I've tested TiffIO, it read wonderfull CMYK, but write this format not....

    I've read, that it is possible to simulate CMYK over the RGBA - Values of a QImage, when set a flag (from RGBA to CMYK) after writing the File....but e can't found a concrete example about this (

    have everybody an idee to solve this problem ?

    I have yet asked Trolltech, but they don't know any way..

    i need the CMYK-format for printing .

    thanks for any help !
    hilby

  2. #2
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    Default Re: writing CMYK-Files from QImage

    I don't think QImage can do that, it is strictly directed at 3 component colour handling.

  3. #3
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    Default Re: writing CMYK-Files from QImage

    Can you just do the calculations yourself? If you want a whole write-up about color spaces, see here: http://www.neuro.sfc.keio.ac.jp/~aly...space-faq.html

    For a short version, the formulas to convert between RGB and CMYK are:
    Black=minimum(1-Red,1-Green,1-Blue)
    Cyan=(1-Red-Black)/(1-Black)
    Magenta=(1-Green-Black)/(1-Black)
    Yellow=(1-Blue-Black)/(1-Black)

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