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Thread: Coloring speccific values in a spectrogram

  1. #1

    Default Coloring speccific values in a spectrogram

    Hello,
    I have the following situation: I have a spectrogram for which I use a color map with color stops. It works fine, but I want to use the color grey for 0 values returned by the value function that needs to be overloaded. The interval in the plot widget may or may not include the zero, but I want all pixels in the spectrogram, where 0 was returned, to be grey. Color stops work only in the interval range, but even if they didn't I need only one value to have a color, not a range of values(even a narrow one).
    How can I accomplish this?
    (attached is a screenshot that shows what I want to do)

    Thank you
    Attached Images Attached Images

  2. #2
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    Default Re: Coloring speccific values in a spectrogram

    You can overload QwtLinearColorMap::rgb() and add some special handling for 0.0 before calling the base class.

    But note that QwtLinearColorMap::rgb() already has this code made for gaps in a spectrogram:

    Qt Code:
    1. if ( qIsNaN(value) )
    2. return qRgba(0, 0, 0, 0);
    To copy to clipboard, switch view to plain text mode 
    So when using NaN instad of 0.0 you would have transparent pixels and you would see the background color of the canvas ( could be gray if you want to ).

    Uwe

  3. #3

    Default Re: Coloring speccific values in a spectrogram

    Excellent! Thank you very much, looks very good.

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