Not all terminals support 24-bit true color—others support only 256 colors, so a conversion must take place. However, when converting from true color to 256, most programs assume that the RGB axes are orthogonal and simply use the Euclidean distance to find the “closest” available color, which produces slightly inaccurate results.

rgbto256 accepts true color input and more accurately converts it to 256 colors using the CIEDE2000 algorithm.

cat misc/example

In a terminal that supports true color, this produces the following:

In a terminal that converts to 256 colors (using a simple Euclidean distance calculation), we get this instead:

However, when piped through rgbto256, the colors are closer to the original image:

cat misc/example | ./utils/rgbto256

Make and GCC must be installed. Then simply run make.

./utils/rgbto256 reads data from standard input and echoes it to standard output, except with true color ANSI escape sequences converted to 256 colors.

For example:

cat misc/example | ./utils/rgbto256

rgbto256 is licensed under version 3 of the GNU Affero General Public License, or (at your option) any later version. See LICENSE.

By contributing to rgbto256, you agree that your contribution may be used according to the terms of rgbto256’s license.