如何使用云功能制作缩略图并将其放置在 Firebase 存储中的特定文件夹中？

Question

这里有一个来自 firebase 的关于如何创建缩略图的示例代码：

https://github.com/firebase/functions-samples/blob/master/quickstarts/thumbnails/functions/index.js

代码是这样的

// [START import]
const functions = require('firebase-functions');
const gcs = require('@google-cloud/storage')();
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((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/')) {
    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;
  }
  // [END stopConditions]

  // [START thumbnailGeneration]
  // Download file from bucket.
  const bucket = gcs.bucket(fileBucket);
  const tempFilePath = path.join(os.tmpdir(), fileName);
  const metadata = {
    contentType: contentType,
  };
  return bucket.file(filePath).download({
    destination: tempFilePath,
  }).then(() => {
    console.log('Image downloaded locally to', tempFilePath);
    // Generate a thumbnail using ImageMagick.
    return spawn('convert', [tempFilePath, '-thumbnail', '200x200>', tempFilePath]);
  }).then(() => {
    console.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.
    return bucket.upload(tempFilePath, {
      destination: thumbFilePath,
      metadata: metadata,
    });
    // Once the thumbnail has been uploaded delete the local file to free up disk space.
  }).then(() => fs.unlinkSync(tempFilePath));
  // [END thumbnailGeneration]
});
// [END generateThumbnail]

但尝试上面的代码后，创建的缩略图似乎位于与原始图像（个人资料图像）相同的文件夹中，如下图所示

如果我希望缩略图位于名为“thumbnail”的不同文件夹中，该怎么办？因此，如果将图像上传到“profileImage”文件夹，缩略图将被放置到“thumbnail”文件夹

Answer 1

您需要修改的代码在这里：

const thumbFileName = `thumb_${fileName}`;
const thumbFilePath = path.join(path.dirname(filePath), thumbFileName);
// Uploading the thumbnail.
return bucket.upload(tempFilePath, {
  destination: thumbFilePath,
  metadata: metadata,
});

它正在构建一条指向 Cloud Storage 中文件应上传到的位置的路径thumbFilePath。您可以看到它正在加入 目录filePath和 文件名thumbFileName。 filePath被定义为原始文件开头的位置：

const filePath = object.name; // File path in the bucket.

所有这一切意味着无论原始文件上传到哪里，缩略图都会排列在它旁边。

如果您想更改最终缩略图的位置，请thumbFilePath包含该位置。它可能就像这样简单地改变它：

const thumbFilePath = `thumbnail/${thumbFileName}`

或者任何你需要的东西。