Created
July 20, 2024 05:37
-
-
Save zazaulola/f82029a70d09c870f25bc6efde115a6f to your computer and use it in GitHub Desktop.
Grayscale image halftone dithering
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| onmessage = ({ data: { data, width, height } }) => { | |
| const thresholdMap = [ | |
| [15, 135, 45, 165], | |
| [195, 75, 225, 105], | |
| [60, 180, 30, 150], | |
| [240, 120, 210, 90], | |
| ]; | |
| let min = 255, | |
| max = 0, | |
| avg = 0, | |
| cnt = 0; | |
| for (let i = 0; i < data.length; i += 4) { | |
| [min, max] = [Math.min(min, data[i]), Math.max(max, data[i])]; | |
| avg += (data[i] - avg) / ++cnt; | |
| } | |
| const threshold = Math.floor((min + max + 2 * avg + 384) / 8); | |
| let i = 0; | |
| for (let y = 0; y < height; y++) { | |
| for (let x = 0; x < width; x++, i += 4) { | |
| const newPixel = Math.floor((data[i] + thresholdMap[x % 4][y % 4]) / 2) > threshold ? 255 : 0; | |
| data[i + 0] = newPixel; | |
| data[i + 1] = newPixel; | |
| data[i + 2] = newPixel; | |
| } | |
| } | |
| postMessage(data); | |
| }; |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment