(function() {
    'use strict';
    /**
    * Grayscale Filter
    * @function
    * @memberof Konva.Filters
    * @param {Object} imageData
    * @example
    * node.cache();
    * node.filters([Konva.Filters.Grayscale]);
    */
    Konva.Filters.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];
            // red
            data[i] = brightness;
            // green
            data[i + 1] = brightness;
            // blue
            data[i + 2] = brightness;
        }
    };
})();