Local Histogram Processing clarification

1. What is local histogram processing?
2. What is the use of local histogram equalization?
3. What is histogram stretching in image processing?

What is local histogram processing?

A local histogram of an image is a histogram of the values of the pixels that lie in a neighborhood of a given pixel's location. It indicates the particular combination of pixel intensities or colors that appear in that neighborhood.

What is the use of local histogram equalization?

Histogram equalization is a widely used image contrast enhancement method. While global histogram equalization enhances the contrast of the whole image, local histogram equalization can enhance many image details by taking different transformation of the same gray level at different places in the original image.

What is histogram stretching in image processing?

Histogram stretching involves modifying the brightness (intensity) values of pixels in the image according to some mapping function that specifies an output pixel brightness value for each input pixel brightness value. For a grayscale digital image, this process is straightforward.