Contrast stretching is a very simple contrasting technique that is used to improve the contrast in an image by a normalization approach. This technique attempts to "stretch" the range of intensities in the image to span the entire dynamic range desired.

The following equation shows a simple formulation of contrasting by stretching:

One drawback of this technique is that it is mainly used on grayscale images, due to the issues that might creep in because of differential stretching of the three color channels (RGB) thus leading to confusing and inconsistent results.

Another potential reason this method isn't used much in practice is it's over-simplicity. This technique only uses a linear, monotonic transform to perform the stretching, which may not be the best way to contrast an image.