JavaScript Canvas实现图片马赛克处理示例

<!DOCTYPE html>
<html>
  <head>
    <meta charset="UTF-8">
    <title>www.jb51.net JS图片马赛克</title>
    <style type="text/css">
      * {
        margin: 0;
        padding: 0;
      }
      body {
        background-color: grey;
        text-align: center;
      }
      #myCanvas {
        background-color: rgba(250, 0, 0, 0.3);
      }
    </style>
  </head>
  <body>
    <canvas id="myCanvas" width="500" height="400"></canvas>
  </body>
  <script type="text/javascript">
    window.onload = function() {
      var myCanvas = document.getElementById('myCanvas');
      var painting = myCanvas.getContext('2d');
       //生成一个图片节点
      var imgNode = new Image();
      imgNode.src = '1.jpg';
      //调用函数
      drawImg(imgNode);
      function drawImg(imgNode) {
        //图片加载后执行马赛克实现语句：5个一组取到随机像素赋给新图里的五个一组
        imgNode.onload = function() {
          painting.drawImage(imgNode, 0, 0, 250, 400);
          var size = 5;
          //获取老图所有像素点
          var oldImg = painting.getImageData(0, 0, 250, 400)
          //创建新图像素对象
          var newImg = painting.createImageData(250, 400)
          for(var i = 0; i < oldImg.width; i++) {
            for(var j = 0; j < oldImg.height; j++) {
              //从5*5中获取单个像素信息
              var color = getPxInfo(oldImg, Math.floor(i * size + Math.random() * size), Math.floor(j * size + Math.random() * size))
              //写入单个像素信息
              for(var a = 0; a < size; a++) {
                for(var b = 0; b < size; b++) {
                  //              (a,b)
                  setPxInfo(newImg, i * size + a, j * size + b, color);
                }
              }
            }
          }
          painting.putImageData(newImg, 250, 0)
        }
      }
      //读取单个像素信息
      function getPxInfo(imgDate, x, y) {
        var colorArr = [];
        var width = imgDate.width;
        colorArr[0] = imgDate.data[(width * y + x) * 4 + 0]
        colorArr[1] = imgDate.data[(width * y + x) * 4 + 1]
        colorArr[2] = imgDate.data[(width * y + x) * 4 + 2]
        colorArr[3] = imgDate.data[(width * y + x) * 4 + 3]
        return colorArr;
      }
      //写入单个像素信息
      function setPxInfo(imgDate, x, y, colors) {
        //（x,y） 之前有多少个像素点 == width*y + x
        var width = imgDate.width;
        imgDate.data[(width * y + x) * 4 + 0] = colors[0];
        imgDate.data[(width * y + x) * 4 + 1] = colors[1];
        imgDate.data[(width * y + x) * 4 + 2] = colors[2];
        imgDate.data[(width * y + x) * 4 + 3] = colors[3];
      }
    }
  </script>
</html>