How does Gmail display PDF attachments as selectable images?

Other Questions Gmail
1

I’m curious about the tech behind Gmail’s PDF viewer. When I open a PDF attachment, it shows up as PNG images for each page. But here’s the cool part - I can still select the text!

Does anyone know what Google might be using to turn PDF pages into PNGs? And how does text selection work on these images? It’s pretty neat, but I can’t figure out how they’re doing it.

I tried watching the network traffic, but that didn’t give me many clues. If you’ve got any ideas or have worked with similar tech, I’d love to hear your thoughts!

// Example of how it might work (just guessing!)
function convertPdfToImage(pdfFile, pageNumber) {
  const pngImage = magicConverter.toPng(pdfFile, pageNumber);
  return pngImage;
}

function enableTextSelection(pngImage) {
  const textLayer = extractText(pngImage);
  overlayTextLayer(pngImage, textLayer);
}

Any insights would be awesome. Thanks!

2

As someone who’s dabbled in document processing systems, I can shed some light on this. Gmail likely employs a two-pronged approach. First, they convert PDF pages to high-resolution images, probably using a tool like ImageMagick or a custom solution. Simultaneously, they extract the text content and positional data from the PDF. On the client-side, they overlay this extracted text as an invisible layer on top of the image. This creates the illusion of selectable text on an image. The tricky part is maintaining perfect alignment, especially when zooming or on different screen sizes. It’s a clever technique that balances performance with functionality, allowing for quick loading and text searchability without sacrificing visual fidelity.

3

hey there, i’ve worked with pdf stuff before. gmail probably uses some fancy server-side magic to turn pdfs into images. they probably extract the text separately and overlay it on the client side. it’s like a sandwich - image on bottom, invisible text on top. that’s how u can select stuff. pretty cool trick, right? not sure exactly what tools they use, but it’s probly custom google wizardry.

4

I’ve spent some time working with PDF rendering and text extraction in web applications, so I think I can offer a few insights. Gmail’s approach is likely a blend of image conversion and text extraction. On the server side, PDFs are probably rendered to images using tools like Ghostscript or PDF.js. Then they extract the text and its precise positioning data. On the client, these images are displayed while an invisible text layer is overlaid, allowing for text selection. The precision alignment of the text layer with the image is key, and it involves careful mapping of coordinates, especially when zooming in or out. This method is effective and is similar to techniques used in digital publishing.