index.js

/**
 * Copyright 2016 Google Inc. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
'use strict';

// [START import]
const functions = require('firebase-functions');
const admin = require('firebase-admin');
admin.initializeApp()
const spawn = require('child-process-promise').spawn;
const path = require('path');
const os = require('os');
const fs = require('fs');
// [END import]

// [START generateThumbnail]
/**
 * When an image is uploaded in the Storage bucket We generate a thumbnail automatically using
 * ImageMagick.
 */
// [START generateThumbnailTrigger]
exports.generateThumbnail = functions.storage.object().onFinalize(async (object) => {
// [END generateThumbnailTrigger]
  // [START eventAttributes]
  const fileBucket = object.bucket; // The Storage bucket that contains the file.
  const filePath = object.name; // File path in the bucket.
  const contentType = object.contentType; // File content type.
  const metageneration = object.metageneration; // Number of times metadata has been generated. New objects have a value of 1.
  // [END eventAttributes]

  // [START stopConditions]
  // Exit if this is triggered on a file that is not an image.
  if (!contentType.startsWith('image/')) {
    return functions.logger.log('This is not an image.');
  }

  // Get the file name.
  const fileName = path.basename(filePath);
  // Exit if the image is already a thumbnail.
  if (fileName.startsWith('thumb_')) {
    return functions.logger.log('Already a Thumbnail.');
  }
  // [END stopConditions]

  // [START thumbnailGeneration]
  // Download file from bucket.
  const bucket = admin.storage().bucket(fileBucket);
  const tempFilePath = path.join(os.tmpdir(), fileName);
  const metadata = {
    contentType: contentType,
  };
  await bucket.file(filePath).download({destination: tempFilePath});
  functions.logger.log('Image downloaded locally to', tempFilePath);
  // Generate a thumbnail using ImageMagick.
  await spawn('convert', [tempFilePath, '-thumbnail', '200x200>', tempFilePath]);
  functions.logger.log('Thumbnail created at', tempFilePath);
  // We add a 'thumb_' prefix to thumbnails file name. That's where we'll upload the thumbnail.
  const thumbFileName = `thumb_${fileName}`;
  const thumbFilePath = path.join(path.dirname(filePath), thumbFileName);
  // Uploading the thumbnail.
  await bucket.upload(tempFilePath, {
    destination: thumbFilePath,
    metadata: metadata,
  });
  // Once the thumbnail has been uploaded delete the local file to free up disk space.
  return fs.unlinkSync(tempFilePath);
  // [END thumbnailGeneration]
});
// [END generateThumbnail]