canvas学习笔记：小小滴公式，大大滴乐趣

var part_1 = (function(w){
    var dots = [],DOT_SIZE = 2,cube=null;

    var Dot = function(x,y,vx,vy,tox,toy,color){
        this.x=x;
        this.y=y;
        this.vx=vx;
        this.vy=vy;
        this.nextox = tox;
        this.nextoy = toy;
        this.color = color;
        this.visible = true;
        this.globleDown = false;
        this.setEnd(tox , toy);
    }

    Dot.prototype = {
        paint:function(){
            ctx.fillStyle=this.color;
            ctx.fillRect(this.x-DOT_SIZE/2 , this.y-DOT_SIZE/2 , DOT_SIZE , DOT_SIZE);
        },

        setEnd:function(tox , toy){
            this.tox = tox;
            this.toy = toy;
            var yc = this.toy - this.y;
            var xc = this.tox - this.x;
            // this.initjl = Math.sqrt(xc*xc+yc*yc);
        },

        update:function(time){
            this.x += this.vx*time;
            this.y += this.vy*time;

            if(!this.globleDown&&this.y>0){
                var yc = this.toy - this.y;
                var xc = this.tox - this.x;

                this.jl = Math.sqrt(xc*xc+yc*yc);

                var za = 20;

                var ax = za*(xc/this.jl),
                    ay = za*(yc/this.jl),
                    vx = (this.vx+ax*time)*0.97,
                    vy = (this.vy+ay*time)*0.97;

                this.vx = vx;
                this.vy = vy;

                // if(Math.abs(this.vx)<1&&Math.abs(this.vy)<1){
                //     this.y = this.toy
                //     this.x = this.tox
                // }
            }else {
                var gravity = 9.8;
                var vy = this.vy+gravity*time;

                if(this.y>canvas.height){
                    vy = -vy*0.7;
                }

                this.vy = vy;
            }
        },

        loop:function(time){
            this.update(time);
            this.paint();
        }
    }

    

    var animate = function(){
        this.state = "before"
    }

    var ap = animate.prototype;

    ap.init = function(){
        this.osCanvas = document.createElement("canvas");
        var osCtx = this.osCanvas.getContext("2d");

        this.osCanvas.width = 1000;
        this.osCanvas.height = 150;

        osCtx.textAlign = "center";
        osCtx.textBaseline = "middle";
        osCtx.font="70px 微软雅黑,黑体 bold";
        osCtx.fillStyle = "#1D181F"
        osCtx.fillText("WelCome" , this.osCanvas.width/2 , this.osCanvas.height/2-40);
        osCtx.fillText("To wAxes‘ HOME" , this.osCanvas.width/2 , this.osCanvas.height/2+40);
        var bigImageData = osCtx.getImageData(0,0,this.osCanvas.width,this.osCanvas.height);

        dots = [];

        for(var x=0;x<bigImageData.width;x+=2){
            for(var y=0;y<bigImageData.height;y+=2){
                var i = (y*bigImageData.width + x)*4;
                if(bigImageData.data[i+3]>128){
                    var dot = new Dot(
                        Math.random()>0.5?Math.random()*20+10:Math.random()*20+canvas.width-40,
                        -Math.random()*canvas.height*2,
                        0,
                        0,
                        x+(canvas.width/2-this.osCanvas.width/2),
                        y+(canvas.height/2-this.osCanvas.height/2),
                        "rgba("+bigImageData.data[i]+","+bigImageData.data[i+1]+","+bigImageData.data[i+2]+",1)"
                    );
                    dot.setEnd(canvas.width/2,canvas.height/2)
                    dots.push(dot);
                }
            }
        }
        console.log(dots.length)
    }

    ap.changeState = function(){
        var osCtx = this.osCanvas.getContext("2d");
        osCtx.clearRect(0,0,this.osCanvas.width,this.osCanvas.height);
        this.osCanvas.width = 460;
        this.osCanvas.height = 100;

        osCtx.fillStyle="#5C5656"
        osCtx.fillRect(20,20,60,60)

        drawLogo(this.osCanvas , osCtx);

        var bigImageData = osCtx.getImageData(0,0,this.osCanvas.width,this.osCanvas.height);

        var index=0;
        dots.sort(function(a , b){
            return Math.random()-Math.random();
        })
        for(var x=0;x<bigImageData.width;x+=2){
            for(var y=0;y<bigImageData.height;y+=2){
                var i = (y*bigImageData.width + x)*4;
                if(bigImageData.data[i+3]>128){
                        var d = dots[index];
                        if(d){
                            d.setEnd(x+(canvas.width/2-300) , y+50)
                            d.color = "rgba("+bigImageData.data[i]+","+bigImageData.data[i+1]+","+bigImageData.data[i+2]+",1)";
                            index++
                        }
                }
            }
        }

        setTimeout(function(){
            var endindex = index;
            for(var i=0;i<dots.length-endindex;i++){
                if(dots[index]){
                    var d = dots[index];
                    
                    d.globleDown = true;
                    d.vx = Math.random()*100-50;
                }
                index++;
            }
        } , 2000)
    }


    function endState(){
        canvas.width = 600;
        canvas.height = 100;
        canvas.style.display="block";
        canvas.style.top = "50px";
        canvas.style.left = (window.innerWidth-canvas.width)/2+"px";
        cube = new Cube(50);
        cube._initVector(50,50);
    }

    function drawLogo(canvas , ctx){
        ctx.textAlign = "center";
        ctx.textBaseline = "middle";
        ctx.font="65px 微软雅黑,黑体 bold"
        ctx.fillStyle="#E06D2F"
        ctx.fillText("DEMO" , 300 , canvas.height/2)

        ctx.font="40px 微软雅黑,黑体 bold"
        ctx.fillStyle="#405159"
        ctx.fillText("吖猩的" , 160 , canvas.height/2)
        ctx.fillText("小窝" , 420 , canvas.height/2)
    }

    var num = 0;
    ap.update = function(time){
        time = time/100;
        if(this.state==="first"||this.state==="before"){
            var completeNum = 0;
            dots.forEach(function(dot){
                if(dot.visible) dot.loop(time);
                if(dot.jl<5){
                    completeNum++
                }
            });
            if(completeNum>=5*dots.length/6){
                
                if(this.state==="before"){
                    this.state = "first";
                    dots.forEach(function(dot){
                        dot.setEnd(dot.nextox , dot.nextoy);
                    });
                }else {
                    this.state = "second";
                    this.changeState();
                }
            }
        }else if(this.state==="second"){
            var completeNum = 0,
                allnum = 0;
            dots.forEach(function(dot){
                if(dot.visible) dot.loop(time);
                if(dot.globleDown){
                    allnum++;
                    if(Math.abs(dot.y-canvas.height)<2){
                        completeNum++
                    }
                }
            });

            if(completeNum===allnum&&allnum!==0){
                this.state = "third";
                part_2.animate();
                endState();
            }
        }else if(this.state==="third"){
            cube.update();
            drawLogo(canvas , ctx);
        }
    }

    return new animate();
})(window)