Histogram Equalization

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Histogram equalization increases the global contrast of an image, especially when the majority of histogram bins are in a small range. After performing histogram equalization, the image intensities are more evenly distributed throughout the histogram. This can be very helpful, especially with under- or over-exposed images.

The Histogram Equalization tool.

Equalize RGB channels This performs histogram equalization on each red, green and blue channel individually. In some cases, this can lead to an unwanted color shift.

Equalize Luminance channel After converting the image to the HSL color space, histogram equalization is done on the luminance channel (L) only. Then the image is converted back to RGB.

Equalize Value channel This converts the image to HSV color space, then does histogram equalization on the value channel (V) only. The image is then converted back to RGB.