How to estimate optimal gamma parameter for gamma correction?

Question

Is it possible to estimate optimal gamma parameter for gamma correction by algorithm using some image statistics? By 'optimal' I mean that image should 'look good' for human on average after correction.

Answer 1

If your image pixels are scaled on the range 0..255, you could use:

gamma = log(mean)/log(128)

where mean is the mean of your image pixels. If they are scaled on the range 0..1:

gamma = log(mean)/log(0.5)

Note that this is the technique that ImageMagick uses, documentation here, and you can test it yourself on the command line with:

magick input.jpg -auto-gamma result.jpg

Nothing is perfect though and that may not look good if there are heavy shadows or bright areas in your images.