RGB2PCT(1)                           GDAL                           RGB2PCT(1)

NAME
       rgb2pct - Convert a 24bit RGB image to 8bit paletted.

SYNOPSIS

          rgb2pct [--help] [--help-general] [--creation-option OPTION]
                     [-n colors | -pct palette_file] [-of format] <source_file> <dest_file>

DESCRIPTION
       This utility will compute an optimal pseudo-color table for a given RGB
       image using a median cut algorithm on a downsampled RGB histogram.
       Then it converts the image into a pseudo-colored image using the color
       table.  This conversion utilizes Floyd-Steinberg dithering (error
       diffusion) to maximize output image visual quality.

       NOTE:
          rgb2pct is a Python utility, and is only available if GDAL Python
          bindings are available.

       TIP:
          Equivalent in new "gdal" command line interface:

          See gdal raster rgb-to-palette.

       --help Show this help message and exit

       --help-general
              Gives a brief usage message for the generic GDAL commandline
              options and exit.

       -n <color>
              Select the number of colors in the generated color table.
              Defaults to 256.  Must be between 2 and 256.

       --creation-option OPTION
              Optional creation parameters for the GeoTIFF driver, for example
              "COMPRESS=LZW". Can be specified multiple times.

       -pct <palette_file>
              Extract the color table from <palette_file> instead of computing
              it.  Can be used to have a consistent color table for multiple
              files.  The <palette_file> must be either a raster file in a
              GDAL supported format with a palette or a color file in a
              supported format (txt, qml, qlr).

       -of <format>
              Select the output format. If not specified, the format is
              guessed from the extension. Use the short format name. Only
              output formats supporting pseudo-color tables should be used.

       <source_file>
              The input RGB file.

       <dest_file>
              The output pseudo-colored file that will be created.

EXAMPLE
       If it is desired to hand create the palette, likely the simplest text
       format is the GDAL VRT format.  In the following example a VRT was
       created in a text editor with a small 4 color palette with the RGBA
       colors 238/238/238/255, 237/237/237/255, 236/236/236/255 and
       229/229/229/255.

          $ rgb2pct -pct palette.vrt rgb.tif pseudo-colored.tif
          $ more < palette.vrt
          <VRTDataset rasterXSize="226" rasterYSize="271">
              <VRTRasterBand dataType="Byte" band="1">
                  <ColorInterp>Palette</ColorInterp>
                  <ColorTable>
                  <Entry c1="238" c2="238" c3="238" c4="255"/>
                  <Entry c1="237" c2="237" c3="237" c4="255"/>
                  <Entry c1="236" c2="236" c3="236" c4="255"/>
                  <Entry c1="229" c2="229" c3="229" c4="255"/>
                  </ColorTable>
              </VRTRasterBand>
          </VRTDataset>

AUTHOR
       Frank Warmerdam <warmerdam@pobox.com>

COPYRIGHT
       1998-2026

                               February 9, 2026                     RGB2PCT(1)