Halftone

Halftone applies dithering to images. Dithering reduces the number of distinct tones or colours in a picture and spreads the resulting error across neighbouring pixels as a pattern, so that gradients survive as visible texture instead of flat bands. The effect is the grainy, printed appearance familiar from newspaper reproduction and early computer displays, and the same technique is used practically when artwork has to fit a restricted palette.

The program works on image files that are already on the machine: an input picture goes in, a converted picture comes out. It is published by tfuxu under the GPL-3.0-or-later licence, so the source can be read, altered and redistributed on those terms.

Scope is narrow by design. Halftone covers the reduction step and is listed for Linux only, so a general image editor is still needed for cropping, colour correction and other preparation work.