js压缩图片base64长度

 1 var myCanvas=$('.img-container > img').cropper('getCroppedCanvas');
 2 (function (base64){
 3     var image = new Image(),newBase64,MAX_HEIGHT = 160;
 4     image.onload = function(){
 5         var canvas = document.getElementById("myCanvas");
 6         if(image.height > MAX_HEIGHT) {
 7             image.width *= MAX_HEIGHT / image.height;
 8             image.height = MAX_HEIGHT;
 9         }
10         var ctx = canvas.getContext("2d");
11         ctx.clearRect(0, 0, canvas.width, canvas.height);
12         canvas.width = image.width;
13         canvas.height = image.height;
14         ctx.drawImage(image, 0, 0, image.width, image.height);
15         newBase64=canvas.toDataURL('image/jpeg',0.4);
　　　　　　//上传base64编码
16         $.ajax({
17             type: "post",
18             url: '地址',
19             data: {
20                 
21             },
22             success: function (msg) {
23                42             },
43             error: function (msg) {
44                 tips.error('上传图片服务出错，请稍候再试。')
45             }
46         });
47         console.log('base64Size',newBase64.length/1024);50     };
51     image.src = base64;
52 })(myCanvas.toDataURL('image/jpeg'));

js压缩图片base64长度，不适于与高质量图片；

通过原base64编码在canvas中绘制新图片，并取出canvas使用toDataUrl方法得到新的base64；

绘制图片时通过改变原图片大小和toDataUrl中参数控制图片质量