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About

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The package provides the following dithering algorithm presets (can also be very easily extended via definition of custom kernels):

  • Atkinson
  • Bayes (ordered dithering w/ customizable sizes & levels)
  • Burkes
  • Diffusion (1D row/column, 2D)
  • Floyd-Steinberg
  • Jarvis-Judice-Ninke
  • Sierra 2-row
  • Stucki
  • Threshold

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Installation

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Dependencies

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API

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import { imageFromURL, intBufferFromImage, GRAY8 } from "@thi.ng/pixel";
import { ditherWith, ATKINSON } from "@thi.ng/pixel-dither";

// create pixel buffer from HTML image element
const img = intBufferFromImage(await imageFromURL("test.jpg"));

// apply dithering to all channels in given pixel buffer
ditherWith(ATKINSON, img);

// first convert to 8-bit gray before dithering
ditherWith(ATKINSON, img.as(GRAY8));

// ...or apply dithering to select channels only
// use custom threshold & error spillage/bleed factor
ditherWith(ATKINSON, img, { channels: [1, 2, 3], threshold: 0.66, bleed: 0.75 });

Custom dither kernels

All bundled algorithm presets (apart from orderedDither()) are implemented as DitherKernel configurations for, defining how each dithered pixel's error should be diffused/distributed to neighbors. This approach makes it very easy to define custom dither configs, like so:

import { ditherWith, type DitherKernel } from "@thi.ng/pixel-dither";

const CUSTOM: DitherKernel = {
    // X offsets of neighbor pixels to update
    ox: [1],
    // Y offsets of neighbor pixels to update
    oy: [1],
    // error weights for updated pixels
    weights: [1],
    // bit shift (scale factor)
    shift: 1,
};

ditherWith(CUSTOM, img);

The above config will distribute the error to a single pixel @ offset (1,1). However the error will be bit-shifted by 1 bit to the right (aka division-by-2). In code form:

pixels[i + ox + oy * width] += (err * weight) >> shift;

Important: Ensure the offset positions only refer to still unprocessed pixels, i.e. those to the right and/or below the currently processed pixel (in following rows).

You can see the result of this kernel in the pixel-dither demo.