基于画布canvas进行图片压缩

【基于画布canvas进行图片压缩 - CSDN App】http://t.csdnimg.cn/JPVM3

vantUi上传压缩案例

dataURLtoFile(dataurl, filename) {
      // 将base64转换为file文件
      let arr = dataurl.split(",");
      let mime = arr[0].match(/:(.*?);/)[1];
      let bstr = atob(arr[1]);
      let n = bstr.length;
      let u8arr = new Uint8Array(n);
      while (n--) {
        u8arr[n] = bstr.charCodeAt(n);
      }
      return new File([u8arr], filename, { type: mime });
    },

    async clzpAfterRead(file) {
      // 大于2MB的图片都缩小像素上传
      console.log(file.file.size, "2097152");
      //2097152
      if (file.file.size > 2097152) {
        let canvas = document.createElement("canvas"); // 创建Canvas对象(画布)
        let context = canvas.getContext("2d");
        let img = new Image();
        img.src = file.content; // 指定图片的DataURL(图片的base64编码数据)
        img.onload = async () => {
          canvas.width = 400;
          canvas.height = 300;
          context.drawImage(img, 0, 0, 400, 300);
          file.content = canvas.toDataURL(file.file.type, 0.92); // 0.92为默认压缩质量
          let files = this.dataURLtoFile(file.content, file.file.name);
          console.log(files, "2097152");
          await this.uploadImg(files);
        };
      } else {
        //小于2M直接上传
        await this.uploadImg(file.file);
      }
    },

    //上传
    uploadImg(file) {
      const formData = new FormData();
      formData.append("file", file);
      formData.append("bizBelongTo", this.bizBelongTo);
      apiStoreManagement
        .uploadShopImage(formData, {
          headers: {
            "Content-Type": "multipart/form-data",
          },
        })
        .then((res) => {
          if (res.code == "0000") {
            if (file instanceof Array) {
              //判断是否是数组
              file.map((v, i) => {
                v.status = "success";
                v.message = "";
                v.url = res.data[i];
                v.id = null;
              });
            } else {
              file.status = "success";
              file.message = "";
              file.url = res.data.imageUrl;
              if (this.bizBelongTo == 1) {
                this.signBoardImageList.push({
                  imagePath: res.data.imagePath,
                  fileSortNo: 1,
                  id: null,
                });
              } else {
                this.fullViewImageList.push({
                  imagePath: res.data.imagePath,
                  fileSortNo: this.fullViewImageList.length + 1,
                  id: null,
                });
              }
            }
          } else {
            return Promise.reject(res);
          }
        })
        .catch((err) => {
          Toast.fail(err.msg || "上传失败");
        });
    },