How to pass the current window screenshot and convert the data base64 into png format to the server

export default {
data() {
 return {
   image: '' //Storage data  }
}
 mounted() {
  setTimeout(() => {
      // Get the id of the position you need to intercept in the current dom      const dom = ("#cesium canvas");
      if (dom) {
        // Convert the selected dom element to a DataURL string in PNG format, print it out as base64 data         = ("image/png");
      }
   },500)
 }
}

methods: {
     base64ImgtoFile(dataurl, filename = "file") {
      return new Promise((resolve, reject) => {
        const image = new Image();
         = dataurl;
         = () => {
          const canvas = ("canvas");
           = ;
           = ;
          const context = ("2d");
          (image, 0, 0);
          ((blob) => {
            const file = new File([blob], `${filename}.png`, {
              type: "image/png"
            });
            resolve(file);
          }, "image/png");
        };
         = (error) => reject(error);
      });
    },
    async convertBase64ToPNG(dataurl, fileName) {
      try {
        const file = await this.base64ImgtoFile(dataurl, fileName);
        // Use the converted file for subsequent operations        return file;
      } catch (error) {
        (error);
      }
    },
}

<template>
  <el-button @click="handleSaveMap">submit</el-button>
</template>
<script>
export default {
  data() {
    return {
      image: "" //Storage data    };
  },
  mounted() {
    setTimeout(() => {
      // Get the id of the position you need to intercept in the current dom      const dom = ("#cesium canvas");
      if (dom) {
        // Convert the selected dom element to a DataURL string in PNG format, print it out as base64 data         = ("image/png");
      }
    }, 500);
  },
  methods: {
    base64ImgtoFile(dataurl, filename = "file") {
      return new Promise((resolve, reject) => {
        const image = new Image();
         = dataurl;
         = () => {
          const canvas = ("canvas");
           = ;
           = ;
          const context = ("2d");
          (image, 0, 0);
          ((blob) => {
            const file = new File([blob], `${filename}.png`, {
              type: "image/png"
            });
            resolve(file);
          }, "image/png");
        };
         = (error) => reject(error);
      });
    },
    async convertBase64ToPNG(dataurl, fileName) {
      try {
        const file = await this.base64ImgtoFile(dataurl, fileName);
        // Use the converted file for subsequent operations        return file;
      } catch (error) {
        (error);
      }
    },
    //Storage data to the server    async generateImages(image) {
      const file = new FileReader(); // Create an object      (image); // Read the file      const res = await (image); // Docking and uploading interface      const { object, msg, success } = ;
      if (success) {
         = ;
      } else this.$(msg);
    },
    // Save data    async handleSaveMap() {
      const loading = this.$loading({
        lock: true,
        text: "Save, please wait...",
        spinner: "el-icon-loading",
        background: "rgba(0, 0, 0, 0.7)"
      });
      // Intercept the current window data      await ();
      // Convert the current base64 image data to png      let image = await this.convertBase64ToPNG(, );
      //Storage to the server      if (image) {
        await (image);
        (, "");
      }
      ();
    }
  }
};
</script>