Image Processing Toolbox User's Guide

Intensity Adjustment

Image enhancement techniques are used to improve an image, where "improve" is sometimes defined objectively (e.g., increase the signal-to-noise ratio), and sometimes subjectively (e.g., make certain features easier to see by modifying the colors or intensities).

Intensity adjustment is an image enhancement technique that maps an image's intensity values to a new range. To illustrate, this figure shows a low-contrast image with its histogram. Notice in the histogram of the image how all the values gather in the center of the range.

• I = imread('pout.tif');
  imshow(I)
  figure, imhist(I,64)
  
  
  

If you remap the data values to fill the entire intensity range [0, 255], you can increase the contrast of the image. The following sections describe several intensity adjustment techniques, including

• Adjusting Intensity Values to a Specified Range
• Histogram Equalization
• Contrast-Limited Adaptive Histogram Equalization
• Decorrelation Stretching

The functions described in this section apply primarily to grayscale images. However, some of these functions can be applied to color images as well. For information about how these functions work with color images, see the reference pages for the individual functions.

Using a Gray-Level Co-Occurrence Matrix (GLCM)

Adjusting Intensity Values to a Specified Range

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