Image histogram stretching

1. What is histogram stretching in image processing?
2. What is image stretching?
3. Is histogram stretching and contrast stretching same?

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.

What is image stretching?

In digital photography, a stretch will expand the range of tonal values used in the output image, so that a larger number of the possible dark to light tones in a given scene are used. A linear stretch will use a formula which is generally applied in the same manner to all pixels in the image.

Is histogram stretching and contrast stretching same?

In Histogram equalization, you want to flatten the histogram into a uniform distribution. In contrast stretching, you manipulate the entire range of intensity values. Like what you do in Normalization. Note that contrast stretching is also called Histogram stretching.