如何使用雲功能制作縮略圖並將其放置在Firebase存儲中的特定文件夾中？

Question

firebase提供了一個有關如何在此處創建縮略圖的示例代碼：

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

代碼是這樣的

// [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]

但是在嘗試了上面的代碼之后，似乎創建的縮略圖與原始圖像（配置文件圖像）位於同一文件夾中，如下圖所示

如果我希望縮略圖位於名為“ thumbnail”的另一個文件夾中，該怎么辦？ 因此，如果將圖像上傳到“ profileImage”文件夾，則縮略圖將放置在“縮略圖”文件夾中

Answer 1

您需要修改的代碼在這里：

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

它正在構建到Cloud Storage中應該在thumbFilePath上傳文件的位置的路徑。 您會看到它正在加入filePath目錄和文件名thumbFileName 。 filePath定義為原始文件在開頭的位置：

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

所有這些意味着，無論原始文件上傳到哪里，縮略圖都會被組織在其旁邊。

如果要更改最終縮略圖的位置，請使thumbFilePath包含該位置。 它可能像這樣更改它一樣簡單：

const thumbFilePath = `thumbnail/${thumbFileName}`

或任何您需要的東西。