I need a script in Google Apps Script to merge two images into one (add a logo or watermark to an image). I've tried using the Slides API and the Document API, but encountered issues.

Attempt #1: Using Slides API

Here’s the script I wrote:

function addLogoToImage() {
  var imageBlob = UrlFetchApp.fetch("https://........jpg").getBlob();
  var logoBlob = UrlFetchApp.fetch("https://......jpg").getBlob();

  const presentation = SlidesApp.create('temp');
  const slide = presentation.getSlides()[0];

  // Add the main image
  slide.insertImage(imageBlob);

  // Add the logo
  slide.insertImage(logoBlob).setWidth(50).setHeight(50).setTop(10).setLeft(10);

  Utilities.sleep(2000);

  // Export the slide as an image
  const presentationId = presentation.getId();
  const exportUrl = `https://docs.google.com/presentation/d/${presentationId}/export/png`;

  const token = ScriptApp.getOAuthToken();
  const response = UrlFetchApp.fetch(exportUrl, {
    headers: {
      Authorization: `Bearer ${token}`,
    },
  });

  const thumbnail = response.getBlob().setName('merged_image.png');
  DriveApp.createFile(thumbnail);

  // Clean up by deleting the presentation
  Drive.Files.remove(presentationId);
}

However, the result is a blank white image of 3 KB in size.

Attempt #2: Using Document API

I also tried the Document API with the following script:

function addLogoWithGoogleDrawings() {
  // Image URLs
  var imageUrl = "https://.........jpg";
  var logoUrl = "https://........jpg";

  // Add the images to a drawing
  var doc = DocumentApp.create("temp");
  var drawingId = doc.getId();
  var body = doc.getBody();
  body.appendImage(UrlFetchApp.fetch(imageUrl).getBlob());
  body.appendImage(UrlFetchApp.fetch(logoUrl).getBlob());

  // Wait for the content to load
  Utilities.sleep(3000);

  // Export as JPG
  const thumbnail = doc.getAs("image/png").setName('merged_image.png');
  DriveApp.createFile(thumbnail);

  // Clean up by deleting the document
  Drive.Files.remove(drawingId);
}

However, as per the documentation, the getAs() method only supports exporting to application/pdf or text/markdown.

Question: Does anyone have an idea how to merge images and export them as a single image file using Google Apps Script? Alternatively, is there a way to fix one of the scripts above?

Bonus...: In the future, I’ll need a similar solution for adding watermarks to videos (e.g., a logo displayed in a corner throughout the video). Any guidance on that would also be greatly appreciated!

Thank you!

Automated Image Merging and Downloading Using Google Apps Script

This script uses the Google Slides API (via SlidesApp) to automate the creation of a Google Slides presentation. It merges two images by first fetching the main image and a logo or watermark.

The script then creates a new Google Slides presentation, inserts the images, and adjusts their sizes and positions.

The slide is saved as a PNG image, which is stored in Google Drive, and the temporary Google Slides presentation is deleted.

Code:

function downloadMergedSlide() {
  var pngFile = mergeAndConvertToPng();

  var html = "<script>window.open('" + pngFile.getDownloadUrl() + "');google.script.host.close();</script>";
  var userInterface = HtmlService.createHtmlOutput(html)
    .setHeight(10)
    .setWidth(100);

  SlidesApp.getUi().showModalDialog(userInterface, 'Downloading PNG ...');

  pngFile.setTrashed(true);
}

function mergeAndConvertToPng() {
  const mainImageURL = "https://........jpg";
  const logoImageURL = "https://........jpg";

  const mainImageBlob = UrlFetchApp.fetch(mainImageURL).getBlob();
  const logoImageBlob = UrlFetchApp.fetch(logoImageURL).getBlob();

  const presentation = SlidesApp.create("Temp Merged Slide");
  const slide = presentation.getSlides()[0];

  const mainImage = slide.insertImage(mainImageBlob);
  mainImage.setWidth(960).setHeight(540).setTop(0).setLeft(0);

  const logoImage = slide.insertImage(logoImageBlob);
  logoImage.setWidth(50).setHeight(50).setTop(10).setLeft(10);

  presentation.saveAndClose();

  const presentationId = presentation.getId();
  const exportUrl = `https://docs.google.com/presentation/d/${presentationId}/export/png`;
  const token = ScriptApp.getOAuthToken();

  const response = UrlFetchApp.fetch(exportUrl, {
    headers: {
      Authorization: `Bearer ${token}`,
    },
    muteHttpExceptions: true,
  });

  if (response.getResponseCode() === 200) {
    const pngBlob = response.getBlob();
    const pngFile = DriveApp.createFile(pngBlob.setName("merged_image.png"));

   
    DriveApp.getFileById(presentationId).setTrashed(true);

    return pngFile;

  }

  return null;
}

Sample Output:

To adjust the size or position of the images, you can change the values of setWidth(), setHeight(), setTop(), and setLeft() for both images.

Reference:

insertImage

getfilebyid

createHtmlOutput(blob)