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 im- age 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 bind- ings 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. RETURN STATUS CODE The program returns status code 0 in case of success, and non-zero in case of error (non-blocking errors emitted as warnings are considered as a suc- cessful execution). EXAMPLE If it is desired to hand create the palette, likely the simplest text for- mat 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 Jun 05, 2026 RGB2PCT(1)
NAME | SYNOPSIS | DESCRIPTION | RETURN STATUS CODE | EXAMPLE | AUTHOR | COPYRIGHT
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