canvas背景登录首页

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html lang="en">
 <head>
  <meta charset="UTF-8">
  <meta name="Generator" content="EditPlus®">
  <meta name="Author" content="">
  <meta name="Keywords" content="">
  <meta name="Description" content="">
  <title>canvas</title>
  <link rel="stylesheet" type="text/css" href="css/rest.css">
  <link rel="stylesheet" type="text/css" href="css/signin.css">
  <link rel="shortcut icon" href="img/icon2.ico"/>
  <meta http-equiv="X-UA-Compatible" content="IE=edge" />
  <style>
    canvas{
        position:fixed;
    }
    .box{

        position:absolute;
        top:50%;
        left:50%;
    }
  </style>
</head>
 </head>
 <body>
  <canvas id="canvas"></canvas>
  <script>
    //定义画布宽高和生成点的个数
    var WIDTH = window.innerWidth, HEIGHT = window.innerHeight, POINT = 35;

    var canvas = document.getElementById('canvas');
    canvas.width = WIDTH,
    canvas.height = HEIGHT;
    var context = canvas.getContext('2d');
    context.strokeStyle = 'rgba(0,0,0,0.03)',
    context.strokeWidth = 1,
    context.fillStyle = 'rgba(0,0,0,0.08)';
    var circleArr = [];

    //线条：开始xy坐标，结束xy坐标，线条透明度
    function Line (x, y, _x, _y, o) {
      this.beginX = x,
      this.beginY = y,
      this.closeX = _x,
      this.closeY = _y,
      this.o = o;
    }
    //点：圆心xy坐标，半径，每帧移动xy的距离
    function Circle (x, y, r, moveX, moveY) {
      this.x = x,
      this.y = y,
      this.r = r,
      this.moveX = moveX,
      this.moveY = moveY;
    }
    //生成max和min之间的随机数
    function num (max, _min) {
      var min = arguments[1] || 0;
      return Math.floor(Math.random()*(max-min+1)+min);
    }
    // 绘制原点
    function drawCricle (cxt, x, y, r, moveX, moveY) {
      var circle = new Circle(x, y, r, moveX, moveY)
      cxt.beginPath()
      cxt.arc(circle.x, circle.y, circle.r, 0, 2*Math.PI)
      cxt.closePath()
      cxt.fill();
      return circle;
    }
    //绘制线条
    function drawLine (cxt, x, y, _x, _y, o) {
      var line = new Line(x, y, _x, _y, o)
      cxt.beginPath()
      cxt.strokeStyle = 'rgba(0,0,0,'+ o +')'
      cxt.moveTo(line.beginX, line.beginY)
      cxt.lineTo(line.closeX, line.closeY)
      cxt.closePath()
      cxt.stroke();

    }
    //初始化生成原点
    function init () {
      circleArr = [];
      for (var i = 0; i < POINT; i++) {
        circleArr.push(drawCricle(context, num(WIDTH), num(HEIGHT), num(15, 2), num(10, -10)/40, num(10, -10)/40));
      }
      draw();
    }

    //每帧绘制
    function draw () {
      context.clearRect(0,0,canvas.width, canvas.height);
      for (var i = 0; i < POINT; i++) {
        drawCricle(context, circleArr[i].x, circleArr[i].y, circleArr[i].r);
      }
      for (var i = 0; i < POINT; i++) {
        for (var j = 0; j < POINT; j++) {
          if (i + j < POINT) {
            var A = Math.abs(circleArr[i+j].x - circleArr[i].x),
              B = Math.abs(circleArr[i+j].y - circleArr[i].y);
            var lineLength = Math.sqrt(A*A + B*B);
            var C = 1/lineLength*7-0.009;
            var lineOpacity = C > 0.03 ? 0.03 : C;
            if (lineOpacity > 0) {
              drawLine(context, circleArr[i].x, circleArr[i].y, circleArr[i+j].x, circleArr[i+j].y, lineOpacity);
            }
          }
        }
      }
    }

    //调用执行
    window.onload = function () {
      init();
      setInterval(function () {
        for (var i = 0; i < POINT; i++) {
          var cir = circleArr[i];
          cir.x += cir.moveX;
          cir.y += cir.moveY;
          if (cir.x > WIDTH) cir.x = 0;
          else if (cir.x < 0) cir.x = WIDTH;
          if (cir.y > HEIGHT) cir.y = 0;
          else if (cir.y < 0) cir.y = HEIGHT;

        }
        draw();
      }, 16);
    }
  </script>
<form class="box" name="reg" action="" method="post">
  <div id="section">
    <div id="logo">
    <a href="class.jsp"><img src="img/ppp.png"></a>
    </div>
    <div id="title">
      在云上收获知识、文档与观点
    </div>

    <div id="sign">
      <div class="input-username">
        <input type="text" name="username" maxlength="30" placeholder="用户名或开发者账号"/> 
      </div>
      <div class="input-password">
        <input type="password" name="password" placeholder="密码" />
      </div>
      <div class="button">
        <button type="submit">登录</button>
      </div>
      <a href="zhuce.jsp"><div class="button1">
      没有账号？注册一个
      </div></a>
    </div>
  </div>
  </form>
 </body>
</html>
这里写图片描述
canvas背景登录首页

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