Dithergo is a simple Go library implementing various dithering algorithm to produce halftone images. It supports color and monochrome image outputs.

The library implements the following dithering methods: Floyd Steinberg, Atkinson, Burkes, Stucki, Sierra-2, Sierra-3, Sierra-Lite. All of these algorithms have something in common: they diffuse the error in two dimensions, but they always push the error forward, never backward.

We can represent this with the following diagram:

         X   7   5 
 3   5   7   5   3
 1   3   5   3   1

       (1/48)

where X represent the current pixel processed. The fraction at the bottom represents the divisor for the error. Above is the the Floyd-Steinberg dithering algorithm which can be transposed into the following Go code:

ditherers = []dither.Dither{
	dither.Dither{
		"FloydSteinberg",
		dither.Settings{
			[][]float32{
				[]float32{ 0.0, 0.0, 0.0, 7.0 / 48.0, 5.0 / 48.0 },
				[]float32{ 3.0 / 48.0, 5.0 / 48.0, 7.0 / 48.0, 5.0 / 48.0, 3.0 / 48.0 },
				[]float32{ 1.0 / 48.0, 3.0 / 48.0, 5.0 / 48.0, 3.0 / 48.0, 1.0 / 48.0 },
			},
			float32(multiplier),
		},
	},
}

You can plug in any dithering algorithm, so the library can be further extended.

$ go get -u -v github.com/esimov/dithergo

Type go run cmd/main.go --help to check all the supported commands. The library supports the following commands:

Usage of commands:
  -e string
    	Generates & exports the color and greyscale mode halftone images. 
	Options: 'all', 'color', 'mono' (default "all")
  -em float
    	Error multiplier (default 1.18)
  -o string
    	Output folder
  -t	Option to export the tresholded image (default true)

You can run all of the supported dithering algorithms at once, or you can run a specific one from the cmd directory.

Input

The below images are generated with the default options using Michelangelo's David statue as sample image.

Color	Monochrome
Atkinson	Atkinson
Burkes	Burkes
Floyd-Steinberg	Floyd-Steinberg
Sierra-2	Sierra-2
Sierra-3	Sierra-3
Sierra-Lite	Sierra-Lite
Stucki	Stucki

• Endre Simo (@simo_endre)

Copyright © 2018 Endre Simo

This software is distributed under the MIT license found in the LICENSE file.