convert a Lisp Machine bitmap file into pgm format
see also :
add an example, a script, a trick and tips
*.iff | *.iff.* | *.ilbm | *.ilbm.* )
*.lispm | *.lispm.* )
Reads a Lisp
Machine bitmap as input. Produces a portable graymap as
This is the
file format written by the tv:write-bit-array-file function
on TI Explorer and Symbolics lisp machines.
bitmaps on lisp machines are color; but the lispm image file
format does not include a color map, so we must treat it as
a graymap instead. This is unfortunate.
bitmap file format is a bit quirky; Usually the image in the
file has its width rounded up to the next higher multiple of
32, but not always. If the width is not a multiple of 32, we
don’t deal with it properly, but because of the Lispm
microcode, such arrays are probably not image data
Also, the lispm
code for saving bitmaps has a bug, in that if you are
writing a bitmap which is not mod32 across, the file may be
up to 7 bits too short! They round down instead of up, and
we don’t handle this bug gracefully.
1991 by Jamie Zawinski and Jef Poskanzer.