canvas数据转化

let imgBase64 = canvas.toDataURL('image/jpeg', 0.8);

let windowURL = window.URL || window.webkitURL;
let imgsrc = windowURL.createObjectURL(e.target.files[0]);

function convertBase64UrlToBlob(base64){
  let bytes=window.atob(urlData.split(',')[1]);        //去掉url的头，并转换为byte; base64编解码(btoa编码,atob解码)
  //处理异常,将ascii码小于0的转换为大于0
  let ab = new ArrayBuffer(bytes.length);
  let ia = new Uint8Array(ab);
  for (let i = 0; i < bytes.length; i++) {
    ia[i] = bytes.charCodeAt(i);
  }
  return new Blob( [ab] , {type : 'image/png'});
}

let imgInfo = event.target.files[0];  //参考javascript/图片上传
let reader = new FileReader();

reader.onload=function(){
   let imgBase64 = this.result;
   console.log(imgBase64);				
}
reader.readAsDataURL(imgInfo);

let canvas = document.createElement('canvas');
canvas.width = 100;
canvas.heigth = 100;
// ...绘图
//1.将canvas转换成base64
let imgBase64 = canvas.toDataURL('image/jpeg', 0.8);

//2.将imgBase64转换Blob
let fileData = convertBase64UrlToBlob(imgBase64);

//3.传到后台
let formData = new FormData();
formData.append('file', fileData);
$.post(url,formData,function(data){
  //上传成功后做某些事
});
	
function convertBase64UrlToBlob(base64){
  let bytes=window.atob(urlData.split(',')[1]);        //去掉url的头，并转换为byte; base64编解码(btoa编码,atob解码)
  //处理异常,将ascii码小于0的转换为大于0
  let ab = new ArrayBuffer(bytes.length);
  let ia = new Uint8Array(ab);
  for (let i = 0; i < bytes.length; i++) {
    ia[i] = bytes.charCodeAt(i);
  }
  return new Blob( [ab] , {type : 'image/png'});
}