konva/lib/filters/Grayscale.js

<p align="center"> <img src="https://konvajs.org/android-chrome-192x192.png" alt="Konva logo" height="180" /> </p>

export const Grayscale = function (imageData) {
    var data = imageData.data, len = data.length, i, brightness;
    for (i = 0; i < len; i += 4) {
        brightness = 0.34 * data[i] + 0.5 * data[i + 1] + 0.16 * data[i + 2];
        data[i] = brightness;
        data[i + 1] = brightness;
        data[i + 2] = brightness;
    }
};