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
        Common  Options  ⟨index.html#commonoptions⟩  ), 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 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.

              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  "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  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  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 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 image, 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 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 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