This program is part of Netpbm.
pnmalias reads a PNM image as input, and applies anti-aliasing to background and foreground pixels. If the input file is a PBM, pnmalias promotes the output anti-aliased image to a PGM, and prints a message informing the user of the change in format.
-bgcolor colorb sets the background color the colorb.
-fgcolor colorf sets the foreground color to colorf.
Pixels with these values will be anti-aliased. By default, pnmalias takes the background color to be black, and foreground color to be white.
Specify the color (color) as described for the argument of the ppm_parsecolor() library routine.
Note that even when dealing with PGMs, background and foreground colors need to be specified in the fashion described above. In this case, pnmalias takes the background and foreground pixel values to be the value of the red component for the specified color.
-bonly says to apply anti-aliasing only to the background pixels.
-fonly says to apply anti-aliasing only to the foreground pixels.
-balias says to apply anti-aliasing to all pixels surrounding background pixels.
-falias says to apply anti-aliasing to all pixels surrounding foreground pixels.
If you specify neither -balias nor -falias, pnmalias applies anti-aliasing only among neighboring background and foreground pixels.
-weight w says to use w as the central weight for the aliasing filter. w must be a real number in the range 0 < w < 1. The lower the value of w is, the "blurrier" the output image is. The default is w = 1/3.