pnmdepth
change the maxval in a portable anymap
see also :
ppmquant - ppmdither
Synopsis
pnmdepth
newmaxval [pnmfile]
add an example, a script, a trick and tips
examples
source
*PBM* )
pnmdepth 255 "$file"
exit 0
;;
*PGM* )
cat "$file"
exit 0
;;
*PPM* )
ppmtopgm "$file"
source
/usr/local/netpbm/bin/pnmdepth 255 | \
/usr/local/netpbm/bin/pnmscale $scale |
\
/usr/local/netpbm/bin/pnmtops -width 8 -height 11 $direction $where
|\
source
ppmtopgm | pnmdepth 255 | \
pnmtops -noturn -width 100 -height 100 > $@ || rm -f $@
%.ps: $(srcdir)/../herds/%.png $(srcdir)/../herds/convol5.pnm
pnmconvol $(srcdir)/../herds/convol5.pnm | ppmtopgm | \
pnmdepth 255 | pnmtops -width 100 -height 100 -noturn
> $@ || rm -f
$@
%.ps: $(srcdir)/../screen/%.png
source
ppmtopgm | pnmdepth 255 | \
pnmtops -noturn -width 100 -height 100 > $@ || rm -f $@
%.ps: $(srcdir)/../herds/%.png $(srcdir)/../herds/convol5.pnm
pnmconvol $(srcdir)/../herds/convol5.pnm | ppmtopgm | \
pnmdepth 255 | pnmtops -width 100 -height 100 -noturn
> $@ || rm -f
$@
%.ps: $(srcdir)/../screen/%.png
source
pgmnorm pgmoil pgmslice pnmarith pnmcut
pnmdepth pnmenlarge pnmfile \\\
pnminterp pnmnoraw pnmscale pnmsplit pnmtofits
pnmtojpeg pnmtopnm pnmtops \\\
description
Reads a
portable anymap as input. Scales all the pixel values, and
writes out the image with the new maxval. Scaling the colors
down to a smaller maxval will result in some loss of
information.
Be careful of
off-by-one errors when choosing the new maxval. For
instance, if you want the color values to be five bits wide,
use a maxval of 31, not 32.
One important
use of pnmdepth is to convert a new format
2-byte-per-sample PNM file to the older 1-byte-per-sample
format. Before April 2000, essentially all raw (binary)
format PNM files had a maxval less than 256 and one byte per
sample, and many programs may rely on that. If you specify a
newmaxval less than 256, the resulting file should be
readable by any program that worked with PNM files before
April 2000.
see also
pnm,
ppmquant , ppmdither
author
Copyright (C)
1989, 1991 by Jef Poskanzer.