Use the Process > Enhancements > Optimize Contrast... command to optimize the image contrast on the basis of the intensity histogram. This command is effective, e.g., if an image contains white or black pixels. In this case, the actual image information will be more clearly contrasted. Using linear mapping the image structures are evenly emphasized.
The dialog box that is opened when you use an image processing operation is made up in the same way for every operation. Click here to switch to a description of this dialog box.
Settings
This command ignores a certain percentage of the brightest and darkest pixels. Use the Left overflow and Right overflow controls to determine this percentage. The intensity range of the remaining pixels will be linearly spread across the maximum possible range of values. Very bright and very dark image areas remain unchanged. The contrast within evenly illuminated image areas will, however, be increased.
Exactly what happens?
With gray-value images the gray value histogram will be measured. The lower and upper 3% of the histogram area will be removed. The remaining histogram will be mapped linearly to cover the maximum value range: 0-255 (8 bit); or 0-65535 (16 bit).
See also
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