Custom WebGL Blend Mode

class Example extends Phaser.Scene
{
    constructor ()
    {
        super();
    }

    preload ()
    {
        this.load.setBaseURL('https://cdn.phaserfiles.com/v410');
        this.load.image('turkey', 'assets/pics/turkey-1985086.jpg');
        this.load.image('face', 'assets/pics/bw-face.png');
        this.load.image('src', 'assets/tests/blendmode/src.png');
        this.load.image('dst', 'assets/tests/blendmode/dst.png');
    }

    create ()
    {
        //  WebGL only:

        var gl = this.sys.game.renderer.gl;

        var consts = [
            gl.ZERO,
            gl.ONE,
            gl.SRC_COLOR,
            gl.ONE_MINUS_SRC_COLOR,
            gl.DST_COLOR,
            gl.ONE_MINUS_DST_COLOR,
            gl.SRC_ALPHA,
            gl.ONE_MINUS_SRC_ALPHA,
            gl.DST_ALPHA,
            gl.ONE_MINUS_DST_ALPHA,
            gl.CONSTANT_COLOR,
            gl.ONE_MINUS_CONSTANT_COLOR,
            gl.CONSTANT_ALPHA,
            gl.ONE_MINUS_CONSTANT_ALPHA,
            gl.SRC_ALPHA_SATURATE
        ];

        var equations = [
            gl.FUNC_ADD,
            gl.FUNC_SUBTRACT,
            gl.FUNC_REVERSE_SUBTRACT
        ];

        var list = [
            { val: 0, text: 'gl.ZERO' },
            { val: 1, text: 'gl.ONE' },
            { val: 2, text: 'gl.SRC_COLOR' },
            { val: 3, text: 'gl.ONE_MINUS_SRC_COLOR' },
            { val: 4, text: 'gl.DST_COLOR' },
            { val: 5, text: 'gl.ONE_MINUS_DST_COLOR' },
            { val: 6, text: 'gl.SRC_ALPHA' },
            { val: 7, text: 'gl.ONE_MINUS_SRC_ALPHA' },
            { val: 8, text: 'gl.DST_ALPHA' },
            { val: 9, text: 'gl.ONE_MINUS_DST_ALPHA' },
            { val: 10, text: 'gl.CONSTANT_COLOR' },
            { val: 11, text: 'gl.ONE_MINUS_CONSTANT_COLOR' },
            { val: 12, text: 'gl.CONSTANT_ALPHA' },
            { val: 13, text: 'gl.ONE_MINUS_CONSTANT_ALPHA' },
            { val: 14, text: 'gl.SRC_ALPHA_SATURATE' }
        ];

        var list2 = [
            { val: 0, text: 'gl.FUNC_ADD' },
            { val: 1, text: 'gl.FUNC_SUBTRACT' },
            { val: 2, text: 'gl.FUNC_REVERSE_SUBTRACT' }
        ];

        var sfactor = gl.ONE;
        var dfactor = gl.ZERO;
        var equation = gl.FUNC_ADD;

        var newMode = [ sfactor, dfactor ];

        var renderer = this.sys.game.renderer;

        var modeIndex = renderer.addBlendMode(newMode, equation);

        this.add.image(400, 300, 'face');
        this.add.image(400, 300, 'dst');
        this.add.image(400, 300, 'src').setBlendMode(modeIndex);

        //  Create some select lists

        var source = $('<select>').attr('id', 'source').appendTo('body');

        $(list).each(function() {
            source.append($("<option>").attr('value', this.val).text(this.text));
        });

        $(source).on('change', function () {

            sfactor = consts[this.value];
            newMode[0] = sfactor;
            renderer.updateBlendMode(modeIndex, newMode, equation);

        });

        var dest = $('<select>').attr('id', 'dest').appendTo('body');

        $(list).each(function() {
            dest.append($("<option>").attr('value', this.val).text(this.text));
        });

        $(dest).on('change', function () {

            dfactor = consts[this.value];
            newMode[1] = dfactor;

            renderer.updateBlendMode(modeIndex, newMode, equation);

        });

        var equ = $('<select>').attr('id', 'equ').appendTo('body');

        $(list2).each(function() {
            equ.append($("<option>").attr('value', this.val).text(this.text));
        });

        $(equ).on('change', function () {

            equation = equations[this.value];

            renderer.updateBlendMode(modeIndex, newMode, equation);

        });

    }

}

const config = {
    scale: { mode: Phaser.Scale.FIT },
    type: Phaser.WEBGL,
    width: 800,
    height: 600,
    parent: 'game-container',
    scene: Example
};

const game = new Phaser.Game(config);