canvas星空文字粒子动画

在学习的时候呢，学习了tween缓动js、requestAnimationFrame动画、canvas中加载特殊字体，还是涨了不少见识，其次，之前因为有ps做动画的经历，所以对帧比较容易理解。这也是第一次做canvas动画，一直以为自己做不好，没想到兴趣让我越来越想做好它。

1.gif

html


<!--这个是因为初始化的时候，特殊字体容易出不来，所以先在这里写出来一下，上面定义一下-->
<h2 class="h2-init-title" style="display: none;">你好,再见。</h2>

<input id="ipt1" class="input-fill1" placeholder="请输入文字" type="text"/>

<canvas id="canvas" width="" height=""></canvas>

  body {
            margin: 0;
            padding: 0;
        }

        canvas {
            display: block;
            background-color:#09080d;
        }

       
        .input-fill1 {
            position: fixed;
            top: 10%;
            left: 35%;
            z-index: 2;
            width:30%;
            border:0 none;
            border-bottom: 1px solid #eee;
            line-height: 30px;
            background-color:transparent; color: #fff;
        }
        .input-fill1:focus{outline: none;}
        @font-face {
            font-family: "ripple";
            src:url('font/brush.ttf') format("truetype");
        }
        .h2-init-title{font-family:'ripple'; }

    var canvas = document.getElementById("canvas");
    canvas.width = window.innerWidth;
    canvas.height = window.innerHeight;
    var ipt1 = document.getElementById("ipt1");
    var cxt = canvas.getContext("2d");
    var imgData, pointsArr = [], colorArr = [], allData = [];


    // 用离屏canvas
    backCanvas = document.createElement("canvas");
    backCanvas.width = canvas.width;
    backCanvas.height = canvas.height;
    backCanvasCtx = backCanvas.getContext('2d');


    Dot= function (x,y) {
        var color = Math.floor(Math.random() * 156);
        var color1 = Math.floor(Math.random() * 256);
        var color2 = Math.floor(Math.random() * 250);
        this.sx=x;
        this.sy=y;
        this.radius=2;
        this.dx=Math.random()*window.innerWidth;
        this.dy=Math.random()*window.innerHeight;
        this.color = 'rgba(' + color + ',' + color1 + ',' + color2 +')';
        // 当前帧
        this.curFrame=0;
        // 总帧数
        this.frameCount=100;

    }

    var obj = {
        aniId:null,
        /**
         * 写文字
         * @param txt
         * @param size
         */
        showText: function (txt, size) {
            backCanvasCtx.textAlign = 'center';
            backCanvasCtx.textBaseline = 'middle';
            backCanvasCtx.save();
            backCanvasCtx.font = size + 'px ripple';
            backCanvasCtx.fillStyle = '#f00';
            backCanvasCtx.fillText(txt, canvas.width / 2, canvas.height / 2);
            backCanvasCtx.restore();

        },
        getPoints: function () {
            var that = this;
            var points=[];
            var imgData = backCanvasCtx.getImageData(0, 0, canvas.width, canvas.height);
            var pixelData = imgData.data;
            for (var nh = 0; nh < backCanvas.height; nh += 5) {
                for (var nw = 0; nw < backCanvas.width; nw += 5) {
                    // 括号内是求出对应位置；*4是像素位置 数组每四个值是一个像素点
                    var num = (nh * backCanvas.width + nw) * 4;
                    if (pixelData[num] != 0) {
                        points.push(new Dot(nw,nh));
                    }
                }
            }
            return points;

        },
        /**
         * 显示粒子
         */
        showLizi: function (v,size) {
            var that=this;
            that.finishCount=0;
            cxt.clearRect(0, 0, canvas.width, canvas.height);
            backCanvasCtx.clearRect(0, 0, canvas.width, canvas.height);
            // 1.在离屏上写红色的字并上下左右居中
            // 2.像素化文字(用任一颜色吧)
            // 3.将其显示到主屏上（找到像素对应坐标，用圆点表示出来）
            that.showText(v, size);
            that.pointList=this.getPoints();
            that.drawDot();

        },
        finishCount:0,
        //tween 动画效果
        /**
         *
         * @param 当前帧
         * @param 开始位置
         * @param 结束位置
         * @param 总共帧数
         * @returns 返回当前帧所在的坐标
         */
        linear: function(t, b, c, d) {
            return c * t / d + b;
        },
        pointList:[],
        drawDot: function () {
            var that=obj;
            cxt.clearRect(0,0,canvas.width,canvas.height);
            for(var k=0;k<that.pointList.length;k++){

                var curDot=that.pointList[k];
                cxt.save();
                cxt.beginPath();

                cxt.fillStyle=curDot.color;

                if(curDot.curFrame<curDot.frameCount){
                     var x=that.linear(curDot.curFrame,curDot.dx,curDot.sx-curDot.dx,curDot.frameCount);
                    var y=that.linear(curDot.curFrame,curDot.dy,curDot.sy-curDot.dy,curDot.frameCount);
                    cxt.arc(x,y,curDot.radius,0,2*Math.PI,false);
                    curDot.curFrame++;
                 }else{
                     cxt.arc(curDot.sx,curDot.sy,curDot.radius,0,2*Math.PI,false);
                     that.finishCount++;
                 }
                cxt.fill();
                cxt.restore();

            }
            if(that.finishCount>=that.pointList.length){
                  cancelAnimationFrame(that.aniId);
//                clearInterval(that.aniId);
                return;
            }



            that.aniId =requestAnimationFrame(that.drawDot);


        }

    };



//    obj.aniId=setInterval(obj.drawDot,20);



    // 默认画面显示hello world
    obj.showLizi('你好，再见。', 160);

    // 按钮操作
    ipt1.onkeyup = function (e) {

        if (e.keyCode == 13) {
            var v = ipt1.value;
            if(!v){
                alert('请输入文字');
                return;
            }
            obj.showLizi(v,100);


        }

    };