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本文介紹了用canvas畫心電圖的示例代碼，分享給大家，具體如下：

效果圖：

思路：

1.模擬點（如果你有真實的數(shù)據(jù)，那就是把數(shù)據(jù)幻化成canvas對應(yīng)的坐標點）

模擬點時注意的點就是高起部分需要對稱以及為了好看要隨機出現(xiàn)上上下下

2.畫線

畫線需要注意有一個勻速移動的過程。

比如 A點到B點，不是簡單的A畫到B，而是A點到A1,A2....最后到B（這一塊按照比例移動比較難）

3.畫線的一些效果，比如加上陰影（這里就可以自由發(fā)揮了）具體代碼

<!DOCTYPE html>
 <html lang="en">
 <head>
     <meta charset="UTF-8">
     <title>心電圖</title>
     <meta name="viewport" content="width=device-width, initial-scale=1, user-scalable=no">
     <style>
         html,body{
             width: 100%;
             height: 100%;
             margin: 0;
         }
         canvas{
             background: #000;
             width: 100%;
            height: 100%;
         }
     </style>
 </head>
 <body>
 <div id="canvas">
     <canvas id="can"></canvas>
 </div>
 <script>
     var can = document.getElementById('can'),
         pan,
         index = 0,
         flag = true,
         wid = document.body.clientWidth,
         hei = document.body.clientHeight,
         x = 0,
         y = hei/2,
         drawX = 0, 
         drawY = hei/2,
         drawXY = [],
         cDrawX = 0,
         i = 0,
         reX = 0,
         reY = 0;
     start();
     function start(){
         can.height = hei;
         can.width  = wid;
         pan = can.getContext("2d");
         pan.strokeStyle = "white";
         pan.lineJoin = "round";
         pan.lineWidth = 6;
         pan.shadowColor = "#228DFF";
         pan.shadowOffsetX = 0;
         pan.shadowOffsetY = 0;
         pan.shadowBlur = 20;
         pan.beginPath();
         pan.moveTo(x,y);
         drawXYS();
         index = setInterval(move,1);
     };

     function drawXYS(){
         if(drawX > wid){
         }else{
             if(drawY == hei/2){
                 if(flag){
                     flag = false;
                 }else{
                     var _y = Math.ceil(Math.random()*10);
                     _y = _y/2;
                     if(Number.isInteger(_y)){
                         drawY += Math.random()*180+30;
                     }else{
                         drawY -= Math.random()*180+30;
                     }
                     flag = true;
                 }
                 cDrawX = Math.random()*40+15;
             }else{
                 drawY = hei/2;
             }
             drawX += cDrawX;
             drawXY.push({
                 x : drawX,
                 y : drawY
             });
             drawXYS();
         }
     }

     function move(){
         var x = drawXY[i].x,
             y = drawXY[i].y;
         if(reX >= x - 1){
             reX = x;
             reY = y;
             i++;
             cc();
             return;
         }
         if(y > hei/2){
             if(reY >= y){
                 reX = x;
                 reY = y;
                 i++;
                 cc();
                 return;
             }
         }else if(y < hei/2){
             if(reY <= y){
                 reX = x;
                 reY = y;
                 i++;
                 cc();
                 return;
             }
         }else{
             reX = x;
             reY = y;
             i++;
             cc();
             return;
         }

         reX += 1;
         if(y == hei/2){
             reY = hei/2;
         }else{
             var c = Math.abs((drawXY[i].x-drawXY[i-1].x)/(drawXY[i].y-drawXY[i-1].y));
             var _yt = (reX-drawXY[i-1].x)/c;

             if(drawXY[i].y < drawXY[i-1].y){
                 reY = drawXY[i-1].y - _yt;
             }else{
                 reY = drawXY[i-1].y + _yt;
             }
         }
         cc();
     }

    function cc(){
        if(i == drawXY.length){
             pan.closePath();
             clearInterval(index);
             index = 0;
             x = 0;
             y = hei/2;
             flag = true;
             i = 0;
         }else{
             pan.lineTo(reX, reY);
             pan.stroke();
         }
    }
 
</script>
</body>
</html>

以上就是本文的全部內(nèi)容，希望對大家的學習有所幫助，也希望大家多多支持腳本之家。

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