konva/lib/filters/Posterize.js

HTML5 2d canvas library for interactive graphics, design editors, whiteboards, and diagrams.

import { Factory } from "../Factory.js";
import { Node } from "../Node.js";
import { getNumberValidator } from "../Validators.js";
/**
 * Posterize Filter. Adjusts the channels so that there are no more
 *  than n different values for that channel. This is also applied
 *  to the alpha channel.
 * @function
 * @name Posterize
 * @author ippo615
 * @memberof Konva.Filters
 * @param {Object} imageData
 * @example
 * node.cache();
 * node.filters([Konva.Filters.Posterize]);
 * node.levels(0.8); // between 0 and 1
 */
export const Posterize = function (imageData) {
    // level must be between 1 and 255
    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);
/**
 * get/set levels.  Must be a number between 0 and 1.  Use with {@link Konva.Filters.Posterize} filter.
 * @name Konva.Node#levels
 * @method
 * @param {Number} level between 0 and 1
 * @returns {Number}
 */