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How to implement the function of uploading and compressing images in js (detailed tutorial)

亚连Original: 2018-06-12 16:36:032687browse

This article mainly introduces the relevant code of js to upload and compress images in detail. It has a certain reference value. Interested friends can refer to it.

The examples in this article share js with everyone. The specific code to implement uploading and image compression is for your reference. The specific content is as follows

Code:

<!DOCTYPE html>
<html>
 <head>
  <meta charset="UTF-8">
  <title></title>
  <script src="https://cdn.bootcss.com/jquery/3.2.1/jquery.min.js"></script>
 </head>
 <body>
  <input type="file" id="picFile" onchange="readFile(this)"/> 
  <img style="" id="img" src="" alt="" />
  <script>
  function readFile(obj){ 
   var file = obj.files[0];  
   //判断类型是不是图片 
    if(!/image\/\w+/.test(file.type)){ 
      alert("请确保文件为图像类型"); 
      return false; 
    } 
    var reader = new FileReader(); 
    reader.readAsDataURL(file); 
    reader.onload = function(e){
     dealImage(this.result,{width:200},function(base){
     　　　　document.getElementById(&#39;img&#39;).setAttribute(&#39;src&#39;,base)
     });
    } 
  } 
 
  /**
   * 图片压缩，默认同比例压缩
   * @param {Object} path
   * pc端传入的路径可以为相对路径，但是在移动端上必须传入的路径是照相图片储存的绝对路径
   * @param {Object} obj
   * obj 对象 有 width， height， quality(0-1)
   * @param {Object} callback
   * 回调函数有一个参数，base64的字符串数据
   */
  function dealImage(path, obj, callback){
   var img = new Image();
   img.src = path;
   img.onload = function(){
   var that = this;
   // 默认按比例压缩
   var w = that.width,
   h = that.height,
   scale = w / h;
   w = obj.width || w;
   h = obj.height || (w / scale);
   var quality = 0.7; // 默认图片质量为0.7
   //生成canvas
   var canvas = document.createElement(&#39;canvas&#39;);
   var ctx = canvas.getContext(&#39;2d&#39;);
   // 创建属性节点
   var anw = document.createAttribute("width");
   anw.nodeValue = w;
   var anh = document.createAttribute("height");
   anh.nodeValue = h;
   canvas.setAttributeNode(anw);
   canvas.setAttributeNode(anh);
   ctx.drawImage(that, 0, 0, w, h);
   // 图像质量
   if(obj.quality && obj.quality <= 1 && obj.quality > 0){
   quality = obj.quality;
   }
   // quality值越小，所绘制出的图像越模糊
   var base64 = canvas.toDataURL(&#39;image/jpeg&#39;, quality );
   // 回调函数返回base64的值
   callback(base64);
   }
  }
  </script>
 </body>
</html>

The above is what I compiled for everyone. I hope it will be helpful to everyone in the future.

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