pnmscale

pnmscale - scale a portable anymap

pnmscale s [pnmfile]
pnmscale -xsize|-width|-ysize| -height s [pnmfile]
pnmscale -xscale|-yscale s [pnmfile]
pnmscale -xscale|-xsize|-width s -yscale|-ysize|-height s [pnmfile]
pnmscale -xysize x y [pnmfile]
pnmscale ?pixels n [pnmfile]

Reads a portable anymap as input. Scales it by the specified factor or factors and produces a portable anymap as output. If the input file is in color, the output will be too, otherwise it will be grayscale. You can both enlarge (scale factor > 1) and reduce (scale factor < 1).

You can specify one dimension as a pixel size, and the other dimension will be scaled correspondingly.

You can specify one dimension as a scale, and the other dimension will not be scaled.

You can specify different sizes or scales for each axis.

You can use the special -xysize flag, which fits the image into the specified size without changing the aspect ratio.

Or, you can use the ?pixels flag, which fits the image into the specified number of pixels without changing the aspect ratio.

All flags can be abbreviated to their shortest unique prefix.

If you enlarge by a factor of 3 or more, you should probably add a pnmsmooth step; otherwise, you can see the original pixels in the resulting image.

pbmreduce(1), pnmenlarge(1), pnmsmooth(1), pnm(5)

Copyright (C) 1989, 1991 by Jef Poskanzer.