# GRASS Help System

i.grey.scale -

The GRASS imagery program that applies a histogram contrast stretch to a map layer is called i.grey.scale. i.grey.scale is actually a contrast enhancement that assigns a histogram contrast stretch grey scale color table to a map layer. The histrogram contrast stretch expands the original range of digital values in the map or image to utilize the full range or sensitivity of the display device. This is done primarily to improve visual image analysis, and may be used prior to computer-assisted clarification, change detection or other raw spectral image analysis because it does not change the original pixel values. As each band file is extracted from tape using the 'i.tape' programs, a histogram contrast stretch grey scale color table is given to each band.

One use for i.grey.scale is to improve the visual interpretation of features within a subset of an already extracted raster file when the subset has low contrast. The contrast stretch algorithm expands the existing range of pixel values (30 to 101) to the full range (0 to 255), making the visual interpretation of the data easier.

Manual entry for i.grey.scale

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Automatically created on: Thu Oct 14 02:12:26 2004