iscale — Image scaler
The iscale command loads any number of input files, reduces their sizes by a given scale factor in both x and y directions, and writes the results to a common output folder.
The scale factor may be specified on the command line following a plus sign. The default is 8.
An integer contrast may be specified to increase the image contrast. This works in a slightly unusual way: If <x> is the average intensity of the image, then a pixel with intensity x is mapped to 128 + c * (x - <x>).
Normally, each output pixel is the average of a block of scale x scale input pixels. If, however, one or more -v arguments are given, the output is instead the | x - <x> | noise in each block.
If an input file is /path/to/file.ext and the scale factor is n, then the output file is /path/to/Snfile.ext.
Exception: if “p=outpath” is specified on the command line, the output file is outpath/Snfile.ext.
iscale is primarily intended for grayscale images. It will run on RGB images as well, but contrast adjustment and variance measurement are not supported.