Ppmtobmp User Manual(1) General Commands Manual Ppmtobmp User Manual(1)
NAME
ppmtobmp - convert a PPM image into a BMP file
SYNOPSIS
ppmtobmp
[-windows]
[-os2]
[-bpp=bits_per_pixel]
[-mapfile=filename]
[ppmfile]
Minimum unique abbreviation of option is acceptable. You may use double
hyphens instead of single hyphen to denote options. You may use white
space in place of the equals sign to separate an option name from its
value.
DESCRIPTION
This program is part of Netpbm(1).
ppmtobmp reads a PPM image as input and produces a Microsoft Windows or
OS/2 BMP file as output.
OPTIONS
In addition to the options common to all programs based on libnetpbm
(most notably -quiet, see ]8;;index.html#commonoptions\ Common Options]8;;\ ), ppmtobmp recognizes the
following command line options:
-windows
Tells the program to produce a Microsoft Windows BMP file. (This
is the default.)
-os2 Tells the program to produce an OS/2 BMP file. (Before August
2000, this was the default).
-bpp This tells how many bits per pixel you want the BMP file to con-
tain. Only 1, 4, 8, and 24 are possible. By default, ppmtobmp
chooses the smallest number with which it can represent all the
colors in the input image. If you specify a number too small to
represent all the colors in the input image, ppmtobmp tells you
and terminates. You can use pnmquant or ppmdither to reduce the
number of colors in the image.
Before Netpbm 10.85 (December 2018), ppmtobmp ignores this option
if the input is PBM and produces a BMP with 1 bit per pixel.
With these versions, if you want more than that, use pbmtopgm to
convert the PBM to PGM first.
-mapfile=filename
This identifies a file to use as the BMP palette (aka "col-
ormap"). In one BMP subformat, the BMP stream contains a palette
of up to 256 colors, and represents the image raster as indices
into that palette. Normally, ppmtobmp takes care of computing a
suitable palette, but if you are going to dissect the BMP output
in some way, you may want certain values for the palette indices.
E.g. you might want red to be 13, where ppmtobmp would (arbitrar-
ily) choose 39. In that case, you can construct the palette
yourself and use this option to tell ppmtobmp to use your
palette.
This option does not control what colors are in the output. The
colors in the output are exactly those in the input, and the
palette you supply must contain at least all the colors that are
in the input. You can use pnmremap to adjust your input image so
that it contains only colors from your palette.
The palette file is a Netpbm format file with one pixel per
palette entry. Each pixel must have a distinct color (no re-
peats). The order of the BMP palette ppmtobmp generates is the
order of the pixels in the palette file, going from top to bot-
tom, left to right.
A BMP palette may have at most 256 colors, so the palette file
must have at most 256 pixels.
You may find pnmcolormap useful in generating the palette file.
pamseq too.
In the case of grayscale image, if you are processing the BMP im-
age, it
may be convenient for you to have the actual gray values in the
raster
part of the image rather than arbitrary indices into a palette.
There is
no BMP format specifically for that, but you can achieve it by
using a
palette in which each index is equal to the indexed gray value,
and then
ignoring the palette when you process the BMP image.
Here is an example of doing that:
$ pamseq 1 255 > mapfile.pgm
$ ppmtobmp -mapfile=mapfile.pgm input.pgm > output.bmp
This option was new in Netpbm 10.45 (December 2008).
NOTES
To get a faithful reproduction of the input image, the maxval of the in-
put image must be 255. If it is something else, the colors in the BMP
file may be slightly different from the colors in the input.
Windows icons are not BMP files. Use ppmtowinicon to create those.
SEE ALSO
bmptoppm(1), ppmtowinicon(1), pnmquant(1), ppmdither(1), pnmremap(1),
ppm(1)
AUTHOR
Copyright (C) 1992 by David W. Sanderson.
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/ppmtobmp.html
netpbm documentation 20 December 2018 Ppmtobmp User Manual(1)
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