pnmscalefixed
Scale a PNM file quickly with possibly reduced quality.
TLDR
Scale an image such that the result has the specified dimensions
$ pnmscalefixed -width [width] -height [height] [path/to/input.pnm] > [path/to/output.pnm]
Scale an image such that the result has the specified width, keeping the aspect ratio
$ pnmscalefixed -width [width] [path/to/input.pnm] > [path/to/output.pnm]
Scale an image such that its width and height is changed by the specified factors
$ pnmscalefixed -xscale [x_factor] -yscale [y_factor] [path/to/input.pnm] > [path/to/output.pnm]
