Image Enhancement

Enhancement algorithms are designed to make a digital image "look better". This is supposed to be objective because to "look better" is different for different people, as well as for different applications, such as computer vision, etc. This is why some of these algorithms may not improve a picture in a human's eyes at all, although some others may drastically alter the picture in such a way that where before, nothing could be made out with the human eye, but after the alteration, objects can be clearly made out. In addition, parameters that work for one picture may not work for another picture. Therefore, Image Enhancement is not guaranteed to do anything except really make a mess of your picture if you don't get the parameters right.

Image enhancement by histogram

The range of pixel intensities in an image can be viewed and manipulated using the Histogram function in image processing programs. In an image the total range of pixel intensity values represents the dynamic range of the detection device and contrast of that image. By mapping the intensity values as a histogram, you can expand or contract the values in the image.

Histogram stretching can be seen as a Window and Level contrast enhancement technique where the window ranges from the minimum to the maximum pixel values of the image.

An important class of point operations is based upon the manipulation of an image histogram or a region histogram.