js压缩图片base64长度

var myCanvas=$('.img-container > img').cropper('getCroppedCanvas');
(function (base64){
    var image = new Image(),newBase64,MAX_HEIGHT = 160;
    image.onload = function(){
        var canvas = document.getElementById("myCanvas");
        if(image.height > MAX_HEIGHT) {
            image.width *= MAX_HEIGHT / image.height;
            image.height = MAX_HEIGHT;
        }
        var ctx = canvas.getContext("2d");
        ctx.clearRect(0, 0, canvas.width, canvas.height);
        canvas.width = image.width;
        canvas.height = image.height;
        ctx.drawImage(image, 0, 0, image.width, image.height);
        newBase64=canvas.toDataURL('image/jpeg',0.4);
　　　　　　//上传base64编码
        $.ajax({
            type: "post",
            url: '地址',
            data: {
                
            },
            success: function (msg) {
               42             },
            error: function (msg) {
                tips.error('上传图片服务出错，请稍候再试。')
            }
        });
        console.log('base64Size',newBase64.length/1024);50     };
    image.src = base64;
})(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