konva/lib/filters/Posterize.js

HTML5 2d canvas library.

import { Factory } from "../Factory.js";
import { Node } from "../Node.js";
import { getNumberValidator } from "../Validators.js";
export const Posterize = function (imageData) {
    const levels = Math.round(this.levels() * 254) + 1, data = imageData.data, len = data.length, scale = 255 / levels;
    for (let i = 0; i < len; i += 1) {
        data[i] = Math.floor(data[i] / scale) * scale;
    }
};
Factory.addGetterSetter(Node, 'levels', 0.5, getNumberValidator(), Factory.afterSetFilter);