asciitopgm — Convert ASCII graphics into a portable graymap
asciitopgm [-d divisor] height width [asciifile]
Reads ASCII data as input. Produces a portable graymap with pixel values that are an approximation of the brightness of the ASCII characters, assuming black-on-white printing. In other words, a capital M is very dark, a period is very light, and a space is white. Input lines that are fewer than width characters are automatically padded with spaces.
The divisor argument is a floating-point number by which the output pixels are divided; the default value is 1.0. This can be used to adjust the brightness of the graymap; for example, if the image is too dim, reduce the divisor.
In keeping with (I believe) FORTRAN line-printer conventions, input lines beginning with a + (plus) character are assumed to overstrike the previous line, allowing a larger range of gray values.
This tool contradicts the message in the pbmtoascii manual: “Note that there is no asciitopbm tool—this transformation is one-way.”