使用Firebase Cloud功能检查存储中是否存在映像

Question

i need your help with one function that i createed to manipulate the images that my users send to my app.

What i need is get the image that the user sent, resize and check if the image was changed to avoid the function to do all again. The examples that i saw change the image name and check if the beggined if the name is equals with the name set, but in my case i need keep the original name of the picture, So, how can i do that? Or exists a better way to solve this problem? My function code is:

  import * as functions from 'firebase-functions';

  import * as Storage from '@google-cloud/storage';
  const gcs = new Storage();

  import { tmpdir } from 'os';
  import { join, dirname } from 'path';

  import * as sharp from 'sharp';
  import * as fs from 'fs-extra';

  export const generateThumbs = functions.storage
  .object()
  .onFinalize(async object => {
    const bucket = gcs.bucket(object.bucket);
    const filePath = object.name;
    const fileName = filePath.split('/').pop();
    const bucketDir = dirname(filePath);

    const workingDir = join(tmpdir(), 'thumbs');
    const tmpFilePath = join(workingDir, 'source.png');

    if (!object.contentType.includes('image')) {
      console.log('exiting function');
      return false;
    }

    // 1. Ensure thumbnail dir exists
    await fs.ensureDir(workingDir);

    // 2. Download Source File
    await bucket.file(filePath).download({
      destination: tmpFilePath
    });

    // 3. Resize the images and define an array of upload promises
    const sizes = [64, 128, 256];

    const uploadPromises = sizes.map(async size => {
      const thumbName = `thumb@${size}_${fileName}`;
      const thumbPath = join(workingDir, thumbName);

      // Resize source image
      await sharp(tmpFilePath)
        .resize(size, size)
        .toFile(thumbPath);

      // Upload to GCS
      return bucket.upload(thumbPath, {
        destination: join(bucketDir, thumbName)
      });
    });

    // 4. Run the upload operations
    await Promise.all(uploadPromises);

    // 5. Cleanup remove the tmp/thumbs from the filesystem
    return fs.remove(workingDir);
  });

Answer 1

If you need to overwrite the original file, and you want to avoid an infinite loop with this function, you could attach custom metadata to the file when you upload it back to Cloud Storage. Then, when the function is invoked again for that file, you can check the metadata on the incoming ObjectMetadata object to know when the function should bail out without making any more changes.