Phaser glow filter

Glow.js

/*jslint white: true*/
/*global Phaser*/

/**
* Defines a glow filter for Web GL.
* @module
*/
Phaser.Filter.Glow = function (game) {
    'use strict';

    Phaser.Filter.call(this, game);

    this.fragmentSrc = [
        'precision lowp float;',
        'varying vec2 vTextureCoord;',
        'varying vec4 vColor;',
        'uniform sampler2D uSampler;',

        'void main() {',
            'vec4 sum = vec4(0);',
            'vec2 texcoord = vTextureCoord;',
            'for(int xx = -4; xx <= 4; xx++) {',
                'for(int yy = -3; yy <= 3; yy++) {',
                    'float dist = sqrt(float(xx*xx) + float(yy*yy));',
                    'float factor = 0.0;',
                    'if (dist == 0.0) {',
                        'factor = 2.0;',
                    '} else {',
                        'factor = 2.0/abs(float(dist));',
                    '}',
                    'sum += texture2D(uSampler, texcoord + vec2(xx, yy) * 0.002) * factor;',
                '}',
            '}',
            'gl_FragColor = sum * 0.025 + texture2D(uSampler, texcoord);',
        '}'
    ];
};

Phaser.Filter.Glow.prototype = Object.create(Phaser.Filter.prototype);
Phaser.Filter.Glow.prototype.constructor = Phaser.Filter.Glow;

module.exports = Phaser.Filter.Glow;