FreeBSD Manual Pages
RGB2PCT(1) GDAL RGB2PCT(1) NAME rgb2pct - Convert a 24bit RGB image to 8bit paletted. SYNOPSIS rgb2pct [--help] [--help-general] [-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 dif- fusion) to maximize output image visual quality. NOTE: rgb2pct is a Python utility, and is only available if GDAL Python bindings are available. --help Show this help message and exit --help-general Gives a brief usage message for the generic GDAL commandline op- tions and exit. -n <color> Select the number of colors in the generated color table. De- faults to 256. Must be between 2 and 256. -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 sup- ported format (txt, qml, qlr). -of <format> Select the output format. Starting with GDAL 2.3, if not speci- fied, the format is guessed from the extension (previously was GTiff). Use the short format name. Only output formats support- ing 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 cre- ated 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 1998-2025 Feb 11, 2025 RGB2PCT(1)
NAME | SYNOPSIS | DESCRIPTION | EXAMPLE | AUTHOR | COPYRIGHT
Want to link to this manual page? Use this URL:
<https://man.freebsd.org/cgi/man.cgi?query=rgb2pct&sektion=1&manpath=FreeBSD+Ports+14.3.quarterly>