使用HTML5的两个api，前端js完成图片压缩。

来源：互联网发布：百度炒股软件编辑：程序博客网时间：2024/05/17 04:40

主要用了两个html5的 API，一个file，一个canvas，压缩主要使用cnavas做的，file是读取文件，之后把压缩好的照片放入内存，最后内存转入表单下img.src，随着表单提交。

照片是自己用单反拍的，5M多，压缩下面3张分别是600多kb，400多kb，300kb的最后那张失真度很大了，压缩效率蛮高的。

<!DOCTYPE html>

<html>
<head>
<meta charset="utf-8"/>
<title>File API Test</title>
<script type="text/javascript" src="js/jquery-1.11.0.min.js"></script>
<script type="text/javascript" src="js/JIC.js"></script>
<style>
#test{
display: none;
}
</style>
</head>
<body>
<input type="file" id="fileImg" >
<form>
<img src="" id="test" alt="">
</form>
<script>
function handleFileSelect (evt) {
// var filebtn = document.getElementById(id);
// console.log(filebtn);
// var files = filebtn.target.files;
// console.log(filebtn.target);
// console.log(files);
var files = evt.target.files;
for (var i = 0, f; f = files[i]; i++) {
 
      // Only process image files.
      if (!f.type.match('image.*')) {
        continue;
      }
 
      var reader = new FileReader();
 
      // Closure to capture the file information.
      reader.onload = (function(theFile) {
        return function(e) {
          // Render thumbnail.
          // console.log(evt.target.files[0]);
          // console.log(e.target);
          console.log(e.target.result);
          var i = document.getElementById("test");
          i.src = event.target.result;
          console.log($(i).width());
          console.log($(i).height());
          $(i).css('width',$(i).width()/10+'px');
          //$(i).css('height',$(i).height()/10+'px');
          console.log($(i).width());
          console.log($(i).height());
          var quality =  50;
          i.src = jic.compress(i,quality).src;
          console.log(i.src);
          i.style.display = "block";
        };
      })(f);
 
      // Read in the image file as a data URL.
      reader.readAsDataURL(f);
    }
  }
 
document.getElementById('fileImg').addEventListener('change', handleFileSelect, false);
</script>
</body>
</html>

var jic = {
        /**
         * Receives an Image Object (can be JPG OR PNG) and returns a new Image Object compressed
         * @param {Image} source_img_obj The source Image Object
         * @param {Integer} quality The output quality of Image Object
         * @return {Image} result_image_obj The compressed Image Object
         */
 
        compress: function(source_img_obj, quality, output_format){
             
             var mime_type = "image/jpeg";
             if(output_format!=undefined && output_format=="png"){
                mime_type = "image/png";
             }
             
 
             var cvs = document.createElement('canvas');
             //naturalWidth真实图片的宽度
             cvs.width = source_img_obj.naturalWidth;
             cvs.height = source_img_obj.naturalHeight;
             var ctx = cvs.getContext("2d").drawImage(source_img_obj, 0, 0);
             var newImageData = cvs.toDataURL(mime_type, quality/100);
             var result_image_obj = new Image();
             result_image_obj.src = newImageData;
             return result_image_obj;
        },
       function   ****(***){}
}

注：原文链接：http://www.gbtags.com/gb/share/2991.htm

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