Histogram Equalization

Histogram equalization is as a contrast enhancement technique with the objective to obtain a new enhanced image with an uniform histogram. This can be achieved by using the normalized cumulative histogram as the grey scale mapping function.

The image shown below has been contrast enhanced by histogram equalization. Also, the intermediate steps of the histogram equalization process are shown, i. e., the histogram and the normalized cumulative histogram. Using the normalized cumulative histogram as a color table of the original image, we obtain the histogram equalized image.

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Left: histogram of the original image, Right: normalized cumulative histogram of the original image

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Left: histogram equalized image, Right: histogram of the histogram equalized image

Due to the discrete nature of the problem, the resultant histogram is not uniform as desired. It is not possible to split a high histogram value into two or more new values.

• Building a visual program (workspace) in cantata
• Execute the visual program equalization.wk