<van-uploader :after-read="onRead" accept="image/*">    <img src="./icon_input_add.png" /> </van-uploader>

data() {    return {      files: {        name: "",        type: ""      },      headerImage: null,      picValue: null,      upImgUrl,    }  },  // 組件方法 獲取 流  async onRead(file) {      // console.log(file);      // console.log(file.file);      this.files.name = file.file.name; // 獲取文件名      this.files.type = file.file.type; // 獲取類型      this.picValue = file.file; // 文件流      this.imgPreview(this.picValue);    },    // 處理圖片    imgPreview(file) {      let self = this;      let Orientation;      //去獲取拍照時的信息，解決拍出來的照片旋轉問題      Exif.getData(file, function () {        Orientation = Exif.getTag(this, "Orientation");      });      // 看支持不支持FileReader      if (!file || !window.FileReader) return;      if (/^image/.test(file.type)) {        // 創建一個reader        let reader = new FileReader();        // 將圖片2將轉成 base64 格式        reader.readAsDataURL(file);        // 讀取成功后的回調        reader.onloadend = function () {          // console.log(this.result);          let result = this.result;          let img = new Image();          img.src = result;          //判斷圖片是否大于500K,是就直接上傳，反之壓縮圖片          if (this.result.length <= 500 * 1024) {            self.headerImage = this.result;            self.postImg();          } else {            img.onload = function () {              let data = self.compress(img, Orientation);              self.headerImage = data;              self.postImg();            };          }        };      }    },    // 壓縮圖片    compress(img, Orientation) {      let canvas = document.createElement("canvas");      let ctx = canvas.getContext("2d");      //瓦片canvas      let tCanvas = document.createElement("canvas");      let tctx = tCanvas.getContext("2d");      // let initSize = img.src.length;      let width = img.width;      let height = img.height;      //如果圖片大于四百萬像素，計算壓縮比并將大小壓至400萬以下      let ratio;      if ((ratio = (width * height) / 4000000) > 1) {        // console.log("大于400萬像素");        ratio = Math.sqrt(ratio);        width /= ratio;        height /= ratio;      } else {        ratio = 1;      }      canvas.width = width;      canvas.height = height;      //    鋪底色      ctx.fillStyle = "#fff";      ctx.fillRect(0, 0, canvas.width, canvas.height);      //如果圖片像素大于100萬則使用瓦片繪制      let count;      if ((count = (width * height) / 1000000) > 1) {        // console.log("超過100W像素");        count = ~~(Math.sqrt(count) + 1); //計算要分成多少塊瓦片        //      計算每塊瓦片的寬和高        let nw = ~~(width / count);        let nh = ~~(height / count);        tCanvas.width = nw;        tCanvas.height = nh;        for (let i = 0; i < count; i++) {          for (let j = 0; j < count; j++) {            tctx.drawImage(img, i * nw * ratio, j * nh * ratio, nw * ratio, nh * ratio, 0, 0, nw, nh);            ctx.drawImage(tCanvas, i * nw, j * nh, nw, nh);          }        }      } else {        ctx.drawImage(img, 0, 0, width, height);      }      //修復ios上傳圖片的時候 被旋轉的問題      if (Orientation != "" && Orientation != 1) {        switch (Orientation) {          case 6: //需要順時針（向左）90度旋轉            this.rotateImg(img, "left", canvas);            break;          case 8: //需要逆時針（向右）90度旋轉            this.rotateImg(img, "right", canvas);            break;          case 3: //需要180度旋轉            this.rotateImg(img, "right", canvas); //轉兩次            this.rotateImg(img, "right", canvas);            break;        }      }      //進行最小壓縮      let ndata = canvas.toDataURL("image/jpeg", 0.1);      tCanvas.width = tCanvas.height = canvas.width = canvas.height = 0;      return ndata;    },    // 旋轉圖片    rotateImg(img, direction, canvas) {      //最小與最大旋轉方向，圖片旋轉4次后回到原方向      const min_step = 0;      const max_step = 3;      if (img == null) return;      //img的高度和寬度不能在img元素隱藏后獲取，否則會出錯      let height = img.height;      let width = img.width;      let step = 2;      if (step == null) {        step = min_step;      }      if (direction == "right") {        step++;        //旋轉到原位置，即超過最大值        step > max_step && (step = min_step);      } else {        step--;        step < min_step && (step = max_step);      }      //旋轉角度以弧度值為參數      let degree = (step * 90 * Math.PI) / 180;      let ctx = canvas.getContext("2d");      switch (step) {        case 0:          canvas.width = width;          canvas.height = height;          ctx.drawImage(img, 0, 0);          break;        case 1:          canvas.width = height;          canvas.height = width;          ctx.rotate(degree);          ctx.drawImage(img, 0, -height);          break;        case 2:          canvas.width = width;          canvas.height = height;          ctx.rotate(degree);          ctx.drawImage(img, -width, -height);          break;        case 3:          canvas.width = height;          canvas.height = width;          ctx.rotate(degree);          ctx.drawImage(img, -width, 0);          break;      }    },    //將base64轉換為文件    dataURLtoFile(dataurl) {      var arr = dataurl.split(","),        bstr = atob(arr[1]),        n = bstr.length,        u8arr = new Uint8Array(n);      while (n--) {        u8arr[n] = bstr.charCodeAt(n);      }      return new File([u8arr], this.files.name, {        type: this.files.type      });    },    //這里寫接口     async postImg() {      let file = this.dataURLtoFile(this.headerImage);      let formData = new window.FormData();      formData.append("file", file);      toast_loding(this, "圖片上傳中???");      try {        let res = await util.ajax.post(this.upImgUrl, formData, {          headers: {            "Content-Type": "multipart/form-data"          }        });      } catch (e) {        console.log(e);      }    }