konva/lib/filters/Grayscale.js

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

/**
 * Grayscale Filter
 * @function
 * @memberof Konva.Filters
 * @param {Object} imageData
 * @example
 * node.cache();
 * node.filters([Konva.Filters.Grayscale]);
 */
export const Grayscale = function (imageData) {
    const data = imageData.data, len = data.length;
    for (let i = 0; i < len; i += 4) {
        const brightness = 0.34 * data[i] + 0.5 * data[i + 1] + 0.16 * data[i + 2];
        // red
        data[i] = brightness;
        // green
        data[i + 1] = brightness;
        // blue
        data[i + 2] = brightness;
    }
};