Histogram equalization is a method of adjusting contrast in the field of image processing using image histograms.

Use:

Used to increase the global contrast of many images, especially when the contrast of the useful data of the image is fairly close to each other, by which the luminance can be better distributed on the histogram. This can then be used to enhance local contrast without affecting the overall contrast, and histogram equalization accomplishes this by effectively scaling the commonly used brightness.

Expanded Information

Contrast ratio is the ratio of black to white in a picture, or the gradation level from black to white. The larger the ratio, the more gradation levels from black to white, and thus the richer the color expression. The impact of contrast on the visual effect is very critical, generally speaking, the greater the contrast, the clearer the image, the more vivid colors, while the contrast is small, it will make the whole picture is gray.

Contrast ratio for dynamic video display effect to be more influential, due to the dynamic image of light and dark conversion is relatively fast, the higher the contrast ratio, the human eye is easier to distinguish such a conversion process. The higher the contrast ratio, the easier it is for the human eye to recognize the transition process. The higher the contrast ratio, the more pronounced the advantage in terms of detail, clarity, and high-speed motion in some dark scenes.

Baidu Encyclopedia - Histogram Equalization