// base64 格式          
   getBase64(file) {
        return new Promise(function (resolve, reject) {
            let reader = new FileReader();
            let imgResult = '';
            reader.readAsDataURL(file);
            reader.onload = function () {
                imgResult = reader.result
            };
            reader.onerror = function (error) {
                reject(error)
            };
            reader.onloadend = function () {
                resolve(imgResult)
            }
        })
    },

  //  二进制格式
            dataURItoBlob(dataURI) {
                // base64 解码
                let byteString = window.atob(dataURI.split(',')[1]);
                let mimeString = dataURI.split(',')[0].split(':')[1].split(';')[0];
                let ab = new ArrayBuffer(byteString.length);
                let ia = new Uint8Array(ab);
                for (let i = 0; i < byteString.length; i++) {
                    ia[i] = byteString.charCodeAt(i)
                }
                return new Blob([ab], {type: mimeString})
            },