Manual: ppmtoilbm

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  ),
       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 short‐
       est 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
	       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.

       -fixplanes | -fp b
	      (min 1, max 16) If a normal ILBM is written, it will have exactly  planes.

       -hambits | -hamplanes n
	      (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.

       -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  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 compression method is byterun1.   Compression	 re‐
	      quires  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  as the colormap.  The colormap file also determines the num‐
	      ber 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 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.

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 documented.
	 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-oldenburg.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)