如何向图像添加附加信息？

Question

我是 React 和 Ionic 的新手，并在 this ionic tutorial 的帮助下构建了 Ionic React 照片库应用程序。现在，我还想在图像显示时向图像添加其他信息，例如日期、位置、一些输入字段……但我只是不知道如何。

这是教程中的代码：

import { useState, useEffect } from "react";
import { isPlatform } from '@ionic/react';

import { Camera, CameraResultType, CameraSource, Photo } from '@capacitor/camera';
import { Filesystem, Directory } from '@capacitor/filesystem'
import { Storage } from '@capacitor/storage'
import { Capacitor } from '@capacitor/core';
import internal from "assert";
import { defaultMaxListeners } from "stream";

const PHOTO_STORAGE = "photos";

export function usePhotoGallery() {

  const [photos, setPhotos] = useState<UserPhoto[]>([]);

  useEffect(() => {
    const loadSaved = async () => {
      const {value} = await Storage.get({key: PHOTO_STORAGE });

      const photosInStorage = (value ? JSON.parse(value) : []) as UserPhoto[];
      // If running on the web...
      if (!isPlatform('hybrid')) {
        for (let photo of photosInStorage) {
          const file = await Filesystem.readFile({
            path: photo.filepath,
            directory: Directory.Data
          });
          // Web platform only: Load the photo as base64 data
          photo.webviewPath = `data:image/jpeg;base64,${file.data}`;
        }
      }
      setPhotos(photosInStorage);
    };
    loadSaved();
  }, []);

  const takePhoto = async () => {
    const cameraPhoto = await Camera.getPhoto({
      resultType: CameraResultType.Uri,
      source: CameraSource.Camera,
      quality: 100
    });
    const fileName = new Date().getTime() + '.jpeg';
    const savedFileImage = await savePicture(cameraPhoto, fileName);
    const newPhotos = [savedFileImage, ...photos];
    setPhotos(newPhotos);
    Storage.set({key: PHOTO_STORAGE,value: JSON.stringify(newPhotos)});

  };

  const savePicture = async (photo: Photo, fileName: string): Promise<UserPhoto> => {
    let base64Data: string;
    // "hybrid" will detect Cordova or Capacitor;
    if (isPlatform('hybrid')) {
      const file = await Filesystem.readFile({
        path: photo.path!
      });
      base64Data = file.data;
    } else {
      base64Data = await base64FromPath(photo.webPath!);
    }
    const savedFile = await Filesystem.writeFile({
      path: fileName,
      data: base64Data,
      directory: Directory.Data
    });

    if (isPlatform('hybrid')) {
      // Display the new image by rewriting the 'file://' path to HTTP
      // Details: https://ionicframework.com/docs/building/webview#file-protocol
      return {
        filepath: savedFile.uri,
        webviewPath: Capacitor.convertFileSrc(savedFile.uri),
      };
    }
    else {
      // Use webPath to display the new image instead of base64 since it's
      // already loaded into memory
      return {
        filepath: fileName,
        webviewPath: photo.webPath
      };
    }
  };

  const deletePhoto = async (photo: UserPhoto) => {
    // Remove this photo from the Photos reference data array
    const newPhotos = photos.filter(p => p.filepath !== photo.filepath);

    // Update photos array cache by overwriting the existing photo array
    Storage.set({key: PHOTO_STORAGE, value: JSON.stringify(newPhotos) });

    // delete photo file from filesystem
    const filename = photo.filepath.substr(photo.filepath.lastIndexOf('/') + 1);
    await Filesystem.deleteFile({
      path: filename,
      directory: Directory.Data
    });
    setPhotos(newPhotos);
  };
  
  return {
    deletePhoto,
    photos,
    takePhoto
  };
}

export interface UserPhoto {
  filepath: string;
  webviewPath?: string;
}

export async function base64FromPath(path: string): Promise<string> {
  const response = await fetch(path);
  const blob = await response.blob();
  return new Promise((resolve, reject) => {
    const reader = new FileReader();
    reader.onerror = reject;
    reader.onload = () => {
      if (typeof reader.result === 'string') {
        resolve(reader.result);
      } else {
        reject('method did not return a string')
      }
    };
    reader.readAsDataURL(blob);
  });
}

我设法用Geolocation Plugin 获取了日期和位置，但我不知道如何将其绑定到拍摄的照片...

我假设我必须通过function base64FromPath() 为网络添加所需的数据，const file = await Filesystem.readFile() 为移动设备？然后显示 export interface UserPhoto 部分，但我完全迷失了，不知道从哪里开始。欢迎提出任何建议！

Answer 1

我发现一种方法可能不是最漂亮或最直接的，但它似乎对我有用。

在takePhoto 函数中，我获取位置和日期，然后通过savePicture 函数传递它。在savePicture 函数中，我返回latitude、longitude 和time，因此可以通过loadSaved 对象中的loadSaved 函数访问它。在interface UserPhoto 内部，这3 个变量也需要声明。

如果有人想提出建议，这里是更新后的代码：

import { useState, useEffect } from "react";
import { isPlatform } from '@ionic/react';


import { Geolocation, Geoposition } from '@ionic-native/geolocation';
import { Camera, CameraResultType, CameraSource, CameraDirection, Photo } from '@capacitor/camera';
import { Filesystem, Directory } from '@capacitor/filesystem'
import { Storage } from '@capacitor/storage'
import { Capacitor } from '@capacitor/core';
import { stringify } from "querystring";

const PHOTO_STORAGE = "photos";
export function usePhotoGallery() {

  const [photos, setPhotos] = useState<UserPhoto[]>([]);

  useEffect(() => {
    const loadSaved = async () => {
      const {value} = await Storage.get({key: PHOTO_STORAGE });

      const photosInStorage = (value ? JSON.parse(value) : []) as UserPhoto[];
      // If running on the web...
      if (!isPlatform('hybrid')) {
        for (let photo of photosInStorage) {
          const file = await Filesystem.readFile({
            path: photo.filepath,
            directory: Directory.Data
          });
          // Web platform only: Load the photo as base64 data
          photo.webviewPath = `data:image/jpeg;base64,${file.data}`;
        }
      }
      setPhotos(photosInStorage);
    };
    loadSaved();
  }, []);

  const takePhoto = async () => {
    const position = await Geolocation.getCurrentPosition();
    const latitude = position.coords.latitude
    const longitude = position.coords.longitude
    const time = new Date(position.timestamp).toLocaleString()
    
    const cameraPhoto = await Camera.getPhoto({
      resultType: CameraResultType.Uri,
      source: CameraSource.Camera,
      direction: CameraDirection.Rear,
      quality: 100
    });
    const fileName = new Date().getTime() + '.jpeg';
    const savedFileImage = await savePicture(cameraPhoto, fileName, latitude, longitude, time);
    const newPhotos = [savedFileImage, ...photos];
    setPhotos(newPhotos);
    Storage.set({key: PHOTO_STORAGE,value: JSON.stringify(newPhotos)});
  };

  const savePicture = async (photo: Photo, fileName: string, latitude: number, longitude: number, time:string): Promise<UserPhoto> => {
    let base64Data: string;
    // "hybrid" will detect Cordova or Capacitor;
    if (isPlatform('hybrid')) {
      const file = await Filesystem.readFile({
        path: photo.path!
      });
      base64Data = file.data;
    } else {
      base64Data = await base64FromPath(photo.webPath!);
    }
    console.log("base64Data")
    console.log(base64Data)
    let savedFile = await Filesystem.writeFile({
      path: fileName,
      data: base64Data,
      directory: Directory.Data
    });
    console.log(savedFile)

    if (isPlatform('hybrid')) {
      // Display the new image by rewriting the 'file://' path to HTTP
      // Details: https://ionicframework.com/docs/building/webview#file-protocol
      return {
        filepath: savedFile.uri,
        webviewPath: Capacitor.convertFileSrc(savedFile.uri),
        latitude: latitude,
        longitude: longitude,
        time: time
      };
    }
    else {
      // Use webPath to display the new image instead of base64 since it's
      // already loaded into memory
      return {
        filepath: fileName,
        webviewPath: photo.webPath,
        latitude: latitude,
        longitude: longitude,
        time: time
      };
    }
  };

  const deletePhoto = async (photo: UserPhoto) => {
    // Remove this photo from the Photos reference data array
    const newPhotos = photos.filter(p => p.filepath !== photo.filepath);

    // Update photos array cache by overwriting the existing photo array
    Storage.set({key: PHOTO_STORAGE, value: JSON.stringify(newPhotos) });

    // delete photo file from filesystem
    const filename = photo.filepath.substr(photo.filepath.lastIndexOf('/') + 1);
    await Filesystem.deleteFile({
      path: filename,
      directory: Directory.Data
    });
    setPhotos(newPhotos);
  };

  return {
    deletePhoto,
    photos,
    takePhoto
  };
}

export interface UserPhoto {
  filepath: string;
  webviewPath?: string;
  latitude: number;
  longitude: number;
  time: string;
}

export async function base64FromPath(path: string): Promise<string> {
  const response = await fetch(path);
  const blob = await response.blob();
  //const blob = new Blob(neu)
  return new Promise((resolve, reject) => {
    const reader = new FileReader();
    console.log(reader)
    reader.onerror = reject;
    reader.onload = () => {
      if (typeof reader.result === 'string') {
        resolve(reader.result);
      } else {
        reject('method did not return a string')
      }
    };
    reader.readAsDataURL(blob);
  });
}

访问是在我的 UI.tsx 中，我使用例如 {photo.latitude} 来显示获取的纬度值