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index.js
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index.js
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/**
* 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';
const functions = require('firebase-functions');
const { Storage } = require('@google-cloud/storage');
const path = require('path');
const sharp = require('sharp');
const THUMB_MAX_WIDTH = 200;
const THUMB_MAX_HEIGHT = 200;
const gcs = new Storage();
/**
* When an image is uploaded in the Storage bucket We generate a thumbnail automatically using
* Sharp.
*/
exports.generateThumbnail = functions.storage.object().onFinalize((object) => {
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.
// Exit if this is triggered on a file that is not an image.
if (!contentType.startsWith('image/')) {
console.log('This is not an image.');
return null;
}
// Get the file name.
const fileName = path.basename(filePath);
// Exit if the image is already a thumbnail.
if (fileName.startsWith('thumb_')) {
console.log('Already a Thumbnail.');
return null;
}
// Download file from bucket.
const bucket = gcs.bucket(fileBucket);
const metadata = {
contentType: contentType,
};
// 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);
// Create write stream for uploading thumbnail
const thumbnailUploadStream = bucket.file(thumbFilePath).createWriteStream({metadata});
// Create Sharp pipeline for resizing the image and use pipe to read from bucket read stream
const pipeline = sharp();
pipeline.resize(THUMB_MAX_WIDTH, THUMB_MAX_HEIGHT).max().pipe(thumbnailUploadStream);
bucket.file(filePath).createReadStream().pipe(pipeline);
return new Promise((resolve, reject) =>
thumbnailUploadStream.on('finish', resolve).on('error', reject));
});