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Thread: is there a simple and quick way to convert color images to gray image?

  1. #1
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    Question is there a simple and quick way to convert color images to gray image?

    something like colorimg.togray()

    i didn't find in QImage class

    thx

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    Default Re: is there a simple and quick way to convert color images to gray image?

    Not that I'm aware of. What you will probably need to do is call bits(), which returns a uchar * to the first bit, and then iterate over them all, applying some rgb->grayscale algorithm to each bit. A quick google search found a few simple algorithms, so it shouldn't be too difficult.

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    Default Re: is there a simple and quick way to convert color images to gray image?

    Not sure if there is any direct function...
    but you can iterate over the image pixels and use QColor::qGray to convert the rgb into gray scale

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    Default Re: is there a simple and quick way to convert color images to gray image?

    Iterating over QImage pixels() and converting with QColor would certainly be easier, but I wonder what the performance would be like. It seems like it would be significantly slower than accessing the bits directly, but I don't know if there's any basis for that. I am interested now. Maybe this weekend I will have a chance to try it out myself.

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