//压缩图片方法
function compressImg(file,callback){
var src;
var fileSize = parseFloat(parseInt(file['size'])/1024/1024).toFixed(2);
var read = new FileReader();
read.readAsDataURL(file);
read.onload = function (e) {
var img = new Image();
img.src = e.target.result;
img.onload = function(){
//默认按比例压缩
var w = this.width,
h = this.height;
//生成canvas
var canvas = document.createElement('canvas');
var ctx = canvas.getContext('2d');
var base64;
// 创建属性节点
canvas.setAttribute("width", w);
canvas.setAttribute("height", h);
ctx.drawImage(this, 0, 0, w, h);
if(fileSize<1){
//如果图片小于一兆 那么不执行压缩操作
base64 = canvas.toDataURL(file['type'], 1);
}else if(fileSize>1&&fileSize<2){
//如果图片大于1M并且小于2M 那么压缩0.5
base64 = canvas.toDataURL(file['type'], 0.5);
}else{
//如果图片超过2m 那么压缩0.2
base64 = canvas.toDataURL(file['type'], 0.2);
}
// 回调函数返回file的值
callback(base64);
};
};
};