JS Tutorial – Background Effects Grayscale Ambient Background

Rengga Dev – Collection of hand-picked free vanilla JavaScript background effect code examples: change background color or image, animated, with canvas and etc.

////////////////////////// PARTICLE ENGINE ////////////////////////////////////////
var ParticleEngine = (function() {
    'use strict';

    function ParticleEngine(canvas_id) {
        // enforces new
        if (!(this instanceof ParticleEngine)) {
            return new ParticleEngine(args);
        }
        
        var _ParticleEngine = this;

        this.canvas_id = canvas_id;
        this.stage = new createjs.Stage(canvas_id);
        this.totalWidth = this.canvasWidth = document.getElementById(canvas_id).width = document.getElementById(canvas_id).offsetWidth;
        this.totalHeight = this.canvasHeight = document.getElementById(canvas_id).height = document.getElementById(canvas_id).offsetHeight;
        this.compositeStyle = "lighter";

        this.particleSettings = [{id:"small", num:300, fromX:0, toX:this.totalWidth, ballwidth:3, alphamax:0.4, areaHeight:.5, color:"#F0F0F0", fill:false}, 
                                {id:"medium", num:100, fromX:0, toX:this.totalWidth,  ballwidth:8, alphamax:0.3, areaHeight:1, color:"#C0C0C0", fill:true}, 
                                {id:"large", num:10, fromX:0, toX:this.totalWidth, ballwidth:30,  alphamax:0.2, areaHeight:1, color:"#A0A0A0", fill:true}];
        this.particleArray = [];
        this.lights = [{ellipseWidth:400, ellipseHeight:100, alpha:0.6, offsetX:0, offsetY:0, color:"#D0D0D0"}, 
                        {ellipseWidth:350, ellipseHeight:250, alpha:0.3, offsetX:-50, offsetY:0, color:"#B8B8B8"}, 
                        {ellipseWidth:100, ellipseHeight:80, alpha:0.2, offsetX:80, offsetY:-50, color:"#F8F8F8"}];

        this.stage.compositeOperation = _ParticleEngine.compositeStyle;


        function drawBgLight()
        {
            var light;
            var bounds;
            var blurFilter;
            for (var i = 0, len = _ParticleEngine.lights.length; i < len; i++) {				
                light = new createjs.Shape();
                light.graphics.beginFill(_ParticleEngine.lights[i].color).drawEllipse(0, 0, _ParticleEngine.lights[i].ellipseWidth, _ParticleEngine.lights[i].ellipseHeight);
                light.regX = _ParticleEngine.lights[i].ellipseWidth/2;
                light.regY = _ParticleEngine.lights[i].ellipseHeight/2; 
                light.y = light.initY = _ParticleEngine.totalHeight/2 + _ParticleEngine.lights[i].offsetY;
                light.x = light.initX =_ParticleEngine.totalWidth/2 + _ParticleEngine.lights[i].offsetX;

                blurFilter = new createjs.BlurFilter(_ParticleEngine.lights[i].ellipseWidth, _ParticleEngine.lights[i].ellipseHeight, 1);
                bounds = blurFilter.getBounds();
                light.filters = [blurFilter];
                light.cache(bounds.x-_ParticleEngine.lights[i].ellipseWidth/2, bounds.y-_ParticleEngine.lights[i].ellipseHeight/2, bounds.width*2, bounds.height*2);
                light.alpha = _ParticleEngine.lights[i].alpha;

                light.compositeOperation = "screen";
                _ParticleEngine.stage.addChildAt(light, 0);

                _ParticleEngine.lights[i].elem = light;
            }

            TweenMax.fromTo(_ParticleEngine.lights[0].elem, 10, {scaleX:1.5, x:_ParticleEngine.lights[0].elem.initX, y:_ParticleEngine.lights[0].elem.initY},{yoyo:true, repeat:-1, ease:Power1.easeInOut, scaleX:2, scaleY:0.7});
            TweenMax.fromTo(_ParticleEngine.lights[1].elem, 12, { x:_ParticleEngine.lights[1].elem.initX, y:_ParticleEngine.lights[1].elem.initY},{delay:5, yoyo:true, repeat:-1, ease:Power1.easeInOut, scaleY:2, scaleX:2, y:_ParticleEngine.totalHeight/2-50, x:_ParticleEngine.totalWidth/2+100});
            TweenMax.fromTo(_ParticleEngine.lights[2].elem, 8, { x:_ParticleEngine.lights[2].elem.initX, y:_ParticleEngine.lights[2].elem.initY},{delay:2, yoyo:true, repeat:-1, ease:Power1.easeInOut, scaleY:1.5, scaleX:1.5, y:_ParticleEngine.totalHeight/2, x:_ParticleEngine.totalWidth/2-200});
        }
        
        var blurFilter;
        function drawParticles(){

            for (var i = 0, len = _ParticleEngine.particleSettings.length; i < len; i++) {
                var ball = _ParticleEngine.particleSettings[i];

                var circle;
                for (var s = 0; s < ball.num; s++ )
                {
                    circle = new createjs.Shape();
                    if(ball.fill){
                        circle.graphics.beginFill(ball.color).drawCircle(0, 0, ball.ballwidth);
                        blurFilter = new createjs.BlurFilter(ball.ballwidth/2, ball.ballwidth/2, 1);
                        circle.filters = [blurFilter];
                        var bounds = blurFilter.getBounds();
                        circle.cache(-50+bounds.x, -50+bounds.y, 100+bounds.width, 100+bounds.height);
                    }else{
                        circle.graphics.beginStroke(ball.color).setStrokeStyle(1).drawCircle(0, 0, ball.ballwidth);
                    }
                    
                    circle.alpha = range(0, 0.1);
                    circle.alphaMax = ball.alphamax;
                    circle.distance = ball.ballwidth * 2;
                    circle.ballwidth = ball.ballwidth;
                    circle.flag = ball.id;
                    _ParticleEngine.applySettings(circle, ball.fromX, ball.toX, ball.areaHeight);
                    circle.speed = range(2, 10);
                    circle.y = circle.initY;
                    circle.x = circle.initX;
                    circle.scaleX = circle.scaleY = range(0.3, 1);

                    _ParticleEngine.stage.addChild(circle);
                    

                    animateBall(circle);

                    _ParticleEngine.particleArray.push(circle);
                }
            }	
        }

        this.applySettings = function(circle, positionX, totalWidth, areaHeight)
        {
            circle.speed = range(1, 3);
            circle.initY = weightedRange(0, _ParticleEngine.totalHeight , 1, [_ParticleEngine.totalHeight * (2-areaHeight/2)/4, _ParticleEngine.totalHeight*(2+areaHeight/2)/4], 0.8 );
            circle.initX = weightedRange(positionX, totalWidth, 1, [positionX+ ((totalWidth-positionX))/4, positionX+ ((totalWidth-positionX)) * 3/4], 0.6);
        }

        function animateBall(ball)
        {
            var scale = range(0.3, 1);
            var xpos = range(ball.initX - ball.distance, ball.initX + ball.distance);
            var ypos = range(ball.initY - ball.distance, ball.initY + ball.distance);
            var speed = ball.speed;
            TweenMax.to(ball, speed, {scaleX:scale, scaleY:scale, x:xpos, y:ypos, onComplete:animateBall, onCompleteParams:[ball], ease:Cubic.easeInOut});	
            TweenMax.to(ball, speed/2, {alpha:range(0.1, ball.alphaMax), onComplete:fadeout, onCompleteParams:[ball, speed]});	
        }	

        function fadeout(ball, speed)
        {
            ball.speed = range(2, 10);
            TweenMax.to(ball, speed/2, {alpha:0 });
        }

        drawBgLight();
        drawParticles();
    }

    ParticleEngine.prototype.render = function()
    {
        this.stage.update();
    }

    ParticleEngine.prototype.resize = function()
    {
        this.totalWidth = this.canvasWidth = document.getElementById(this.canvas_id).width = document.getElementById(this.canvas_id).offsetWidth;
        this.totalHeight = this.canvasHeight = document.getElementById(this.canvas_id).height = document.getElementById(this.canvas_id).offsetHeight;
        this.render();

        for (var i= 0, length = this.particleArray.length; i < length; i++)
        {
            this.applySettings(this.particleArray[i], 0, this.totalWidth, this.particleArray[i].areaHeight);
        }

        for (var j = 0, len = this.lights.length; j < len; j++) {
            this.lights[j].elem.initY = this.totalHeight/2 + this.lights[j].offsetY;
            this.lights[j].elem.initX =this.totalWidth/2 + this.lights[j].offsetX;
            TweenMax.to(this.lights[j].elem, .5, {x:this.lights[j].elem.initX, y:this.lights[j].elem.initY});			
        }
    }

    return ParticleEngine;

}());

////////////////////////UTILS//////////////////////////////////////

function range(min, max)
{
    return min + (max - min) * Math.random();
}
        
function round(num, precision)
{
   var decimal = Math.pow(10, precision);
   return Math.round(decimal* num) / decimal;
}

function weightedRange(to, from, decimalPlaces, weightedRange, weightStrength)
{
    if (typeof from === "undefined" || from === null) { 
        from = 0; 
    }
    if (typeof decimalPlaces === "undefined" || decimalPlaces === null) { 
        decimalPlaces = 0; 
    }
    if (typeof weightedRange === "undefined" || weightedRange === null) { 
        weightedRange = 0; 
    }
    if (typeof weightStrength === "undefined" || weightStrength === null) { 
        weightStrength = 0; 
    }

   var ret
   if(to == from){return(to);}
 
   if(weightedRange && Math.random()<=weightStrength){
      ret = round( Math.random()*(weightedRange[1]-weightedRange[0]) + weightedRange[0], decimalPlaces )
   }else{
      ret = round( Math.random()*(to-from)+from, decimalPlaces )
   }
   return(ret);
}

///////////////// RUN CODE //////////////////////////

var particles
(function(){
    particles = new ParticleEngine('projector');
    createjs.Ticker.addEventListener("tick", updateCanvas);
    window.addEventListener('resize', resizeCanvas, false);

    function updateCanvas(){
        particles.render();
    }

    function resizeCanvas(){
        particles.resize();
    }
}());