Question

Compare between histogram equalization histogram specification and contrast stretching

Answer 1

In image processing, histogram matching or histogram specification is the transformation of an image so that its histogram matches a specified histogram.[1] The well-known histogram equalization method is a special case in which the specified histogram is uniformly distributed.[2]

It is possible to use histogram matching to balance detector responses as a relative detector calibration technique. It can be used to normalize two images, when the images were acquired at the same local illumination (such as shadows) over the same location, but by different sensors, atmospheric conditions or global illumination


Contrast Stretching. Background: Contrast stretching (also called Normalization) attempts to improve an image by stretching the range of intensity values it contains to make full use of possible values. Unlike histogram equalization, contrast stretching is restricted to a linear mapping of input to output values.



Histogram equalization is a method in image processing of contrast adjustment using the image's histogram.

1st image:histogram specification
2nd image:histogram equalization

Answer 2

The comparison between histogram equalization, histogram specification, and contrast stretching is as follows:

Histogram Equalization

• Histogram Equalization is an image processing technique.

• It enhances contrast by adjusting the intensities of the image.

• It ensures that an image contains a uniform distribution of intensities.

Histogram Specification

• It is also known as histogram matching.

• It refers to the generalized version of Histogram Equalization.

• It is a transformation technique which ensures that the histogram of an image matches a specified histogram.

Contrast Stretching

• It is often called as normalization.

• It is an image enhancement technique.

• It enhances the contrast of the image by stretching its intensity values.