Updated: 29 October 2008
Table Of Contents
ppmtobmp - convert a PPM image into a BMP file
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.
This program is part of Netpbm.
ppmtobmp reads a PPM image as input and produces a Microsoft
Windows or OS/2 BMP file as output.
- Tells the program to produce a Microsoft Windows BMP file. (This
is the default.)
- Tells the program to produce an OS/2 BMP file. (Before August
2000, this was the default).
- This tells how many bits per pixel you want the BMP file to
contain. 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.
- This identifies a file to use as the BMP palette (aka
"colormap"). 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 (arbitrarily) choose 39. In that case, you can construct the
palette yourself and use this option to tell ppmtobmp to use
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 repeats).
The order of the BMP palette ppmtobmp generates is the order
of the pixels in the palette file, going from top to bottom, left
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.
This option was new in Netpbm 10.45 (December 2008).
To get a faithful reproduction of the input image, the maxval of the
input 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
Copyright (C) 1992 by David W. Sanderson.
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