## Changing the image contrast

Contrast stretch

This image is with the green enhancement

The cyan enhancement produces this image

Since temperatures of meteorological significance rarely exceed 40 º C or decrease below -80 º C, many of the 256 brightness values in the very warm and very cold temperature regions are wasted. A solution to this problem is to assign a brightness value of zero (black) to all temperature values greater than 40 º C and assign a brightness value of 255 (white) to all temperature values less than -80 º C. The range of temperatures between -80 º C and 40 º C will be represented by the 256 brightness values and thus will increase the slope of the diagonal. Representing a smaller temperature range with 256 brightness values improves the contrast in the temperature range, allowing smaller differences in temperature to be detected in the image. Thus this enhancement process is referred to as a contrast stretch.

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