DOKK / manpages / debian 12 / netpbm / ppmtoilbm.1.en
Ppmtoilbm User Manual(1) General Commands Manual Ppmtoilbm User Manual(1)

ppmtoilbm - convert a PPM image into an ILBM file

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]

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.

In addition to the options common to all programs based on libnetpbm (most notably -quiet, see
Common Options ), 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.

(default 5, minimum 1, maximum 16) Maximum planes to write in a normal ILBM. If the image does not fit into <n> planes, ppmtoilbm 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.

(min 1, max 16) If a normal ILBM is written, it will have exactly <n> planes.

(default 6, min 3, max 16) Select number of planes for HAM picture. The current Amiga hardware understands 6 and 8 planes, so for now you should only use this values.

Turns off -hamif/-24if/-dcif, -hamforce/-24force/-dcforce and -cmaponly. Also sets compression type to byterun1.

This is the default.

-24if (*)
Write a HAM/24bit/direct color file if the image does not fit into <maxplanes> planes.

-24force (*)
Write a HAM/24bit/direct color file.

(default 5, min 1, max 16). Select number of bits for red, green and blue in a direct color ILBM.

Shortcut for: -hamplanes 6 -maxplanes 5

This is the default.

Shortcut for: -hamplanes 8 -maxplanes 8

Shortcut for: -hamplanes 6 -hamforce

Shortcut for: -hamplanes 8 -hamforce

This is the default. Compress the BODY chunk. The default compression 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.

This option does the same thing as -compress.

Write a normal ILBM using the colors in <ppmfile> as the colormap. The colormap file also determines the number of planes; -maxplanes and -fixplanes are ignored.

Write a colormap file: only BMHD and CMAP chunks, no BODY chunk, nPlanes = 0.

See the -compress option.

HAM pictures will always get a grayscale colormap; a real color selection algorithm might give better results. On the other hand, this allows 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.

Amiga ROM Kernel Reference Manual - Devices (3rd Ed.) Addison Wesley, ISBN 0-201-56775-X

ppm(1), ilbmtoppm(1)

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 documented.
This is just in case something uses those options, since the cost of
maintaining them is so small.

Copyright (C) 1989 by Jef Poskanzer.

Modified October 1993 by Ingo Wilken (Ingo.Wilken@informatik.uni-oldenburg.de)

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
15 January 2022 netpbm documentation