Ppmtoilbm User Manual(1) General Commands Manual Ppmtoilbm User Manual(1)
NAME
ppmtoilbm - convert a PPM image into an ILBM file
SYNOPSIS
ppmtoilbm
[-maxplanes|-mp N]
[-fixplanes|-fp N]
[-ham6|-ham8]
[{-dcbits|-dcplanes} r g b]
[ -normal|-hamif|-hamforce|-24if|-24force| -dcif|-dcforce|-cmaponly ]
[-ecs|-aga]
[-compress|-nocompress]
[-cmethod type]
[-map ppmfile]
[ppmfile]
DESCRIPTION
This program is part of Netpbm(1).
ppmtoilbm reads a PPM image as input. Produces an ILBM file as output.
ppmtoilbm understands the following ILBM types:
• Normal ILBMs with 1-16 planes
• Amiga HAM with 3-16 planes
• 24 bit
• Color map (BMHD + CMAP chunk only, nPlanes = 0)
• Unofficial direct color. 1-16 planes for each color component.
Chunks written: BMHD, CMAP, CAMG (only for HAM), BODY (not for colormap
files) unofficial DCOL chunk for direct color ILBM.
OPTIONS
In addition to the options common to all programs based on libnetpbm
(most notably -quiet, see
Common Options ⟨index.html#commonoptions⟩ ), ppmtoilbm recognizes the
following command line options:
Options marked with (*) can be prefixed with a "no", e.g. "-nohamif".
All options can be abbreviated to their shortest unique prefix.
-maxplanes | -mp n
(default 5, minimum 1, maximum 16) Maximum planes to write in a
normal ILBM. If the image does not fit into <n> planes, ppm-
toilbm writes a HAM file (if -hamif is used), a 24bit file (if
-24if is used) or a direct color file (if -dcif is used) or
aborts with an error.
-fixplanes | -fp b
(min 1, max 16) If a normal ILBM is written, it will have ex-
actly <n> planes.
-hambits | -hamplanes n
(default 6, min 3, max 16) Select number of planes for HAM pic-
ture. The current Amiga hardware understands 6 and 8 planes, so
for now you should only use this values.
-normal
Turns off -hamif/-24if/-dcif, -hamforce/-24force/-dcforce and
-cmaponly. Also sets compression type to byterun1.
This is the default.
-hamif (*)
-24if (*)
-dcif (*)
Write a HAM/24bit/direct color file if the image does not fit
into <maxplanes> planes.
-hamforce (*)
-24force (*)
-dcforce (*)
Write a HAM/24bit/direct color file.
-dcbits r g b
-dcplanes r g b
(default 5, min 1, max 16). Select number of bits for red,
green and blue in a direct color ILBM.
-ecs Shortcut for: -hamplanes 6 -maxplanes 5
This is the default.
-aga Shortcut for: -hamplanes 8 -maxplanes 8
-ham6 Shortcut for: -hamplanes 6 -hamforce
-ham8 Shortcut for: -hamplanes 8 -hamforce
-compress (*)
This is the default. Compress the BODY chunk. The default com-
pression method is byterun1. Compression requires building the
ILBM image in memory; turning compression off allows stream-
writing of the image, but the resulting file will usually be 30%
to 50% larger. Another alternative is the -savemem option, this
will keep memory requirements for compression at a minimum, but
is very slow.
-cmethod none|byterun1
This option does the same thing as -compress.
-map ppmfile
Write a normal ILBM using the colors in <ppmfile> as the col-
ormap. The colormap file also determines the number of planes;
-maxplanes and -fixplanes are ignored.
-cmaponly
Write a colormap file: only BMHD and CMAP chunks, no BODY chunk,
nPlanes = 0.
-savemem
See the -compress option.
LIMITATIONS
HAM pictures will always get a grayscale colormap; a real color selec-
tion algorithm might give better results. On the other hand, this al-
lows row-by-row operation on HAM images, and all HAM images of the same
depth (no. of planes) share a common colormap, which is useful for
building HAM animations.
REFERENCES
Amiga ROM Kernel Reference Manual - Devices (3rd Ed.) Addison Wesley,
ISBN 0-201-56775-X
SEE ALSO
ppm(1), ilbmtoppm(1)
HISTORY
For about a year in 1993-1994, there was a -savemem option.
There used to be a -floyd (aka -fs) option that was supposed
to cause images to be dithered so that a larger number of colors in
the PPM
input could be represented in a smaller number of colors in the ILBM
output.
But it was never documented. Furthermore, developers discovered in
January
2022 that the code for this was nonfunctional because of defects, and
had
been for a very long time and maybe always. Finally,, this functions
is not
appropriate in the Netpbm philosophy, because dithering should be
done by a
separate dithering program, not a format conversion program. Indeed,
the programs ppmdither, pnmquant, and pnmremap can do
this.
Therefore, since Netpbm 10.98 (March 2022), the dithering code has not
been
in the program and any attempt to use the options fails with a simple
invalid option message. But the -nofloyd and -nofs options
remain, doing nothing as they were designed to do, and still not doc-
umented.
This is just in case something uses those options, since the cost of
maintaining them is so small.
AUTHORS
Copyright (C) 1989 by Jef Poskanzer.
Modified October 1993 by Ingo Wilken (Ingo.Wilken@informatik.uni-olden-
burg.de)
DOCUMENT SOURCE
This manual page was generated by the Netpbm tool 'makeman' from HTML
source. The master documentation is at
http://netpbm.sourceforge.net/doc/ppmtoilbm.html
netpbm documentation 15 January 2022 Ppmtoilbm User Manual(1)
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