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前端压缩图片总的来说还是转base64 然后等比例放小宽和高  这个是上次压缩图片的一个扩展

压缩完之后 再将base64 转成blob再转成文件然后再上传  一生要强的前端崽子（后端不支持base64上传） 自己改吧改吧

 // 图片上传async changePic(e) {this.isshangchuantupian=truethis.$message.warning('图片资源正在压缩...')// 获取图片数据  var file = e.target.files[0];var reader = new FileReader();reader.readAsDataURL(file);let ctempfilelet _that = thisreader.onload = await function (event) {// 压缩图片  var img = new Image();img.src = event.target.result;img.onload = function () {var canvas = document.createElement('canvas');var ctx = canvas.getContext('2d');var width = img.widthvar height = img.heightif (Math.max(width, height) > _that.maximg) {if (width > height) {canvas.width = _that.maximg;canvas.height = _that.maximg * height / width} else {canvas.height = _that.maximgcanvas.width = _that.maximg * width / height}} else {canvas.width = width;canvas.height = height;}ctx.drawImage(img, 0, 0, canvas.width, canvas.height);var dataUrl = canvas.toDataURL('image/jpeg', 0.8); // 压缩后的图片数据  var blob = dataURLToBlob(dataUrl); // 将压缩后的图片数据转换为Blob对象  ctempfile = new File([blob], file.name, { type: 'image/jpeg' }); // 将Blob对象封装为File对象  //console.log(ctempfile)let formData = new FormData()// for (let i = 0; i < fileList.length; i++) {//formData.append('xxxx', fileList[i])//}formData.append('update_image', ctempfile)http.post('服务器地址', formData).then(res => {//console.log(res.data.update_image)if (res.data.xxxx) {_that.isshangchuantupian=false} else {_that.$message({message: '图片上传失败：',type: 'error'})}}).catch(err => {console.log(err)})};};// 将Base64编码的图片数据转换为Blob对象  function dataURLToBlob(dataUrl) {var arr = dataUrl.split(','), mime = arr[0].match(/:(.*?);/)[1];var bstr = atob(arr[1]);var n = bstr.length;var u8arr = new Uint8Array(n);while (n--) {u8arr[n] = bstr.charCodeAt(n);}return new Blob([u8arr], { type: mime });}//let fileList = e.target.files},