1492303 - PDF rendering at high zoom levels is blurry

Status: VERIFIED FIXED

(Firefox :: PDF Viewer, defect, P1)

Description

[googoldinges]

Attachment: https://presspage-production-content.s3.amazonaws.com/uploads/570/spoorkaart-2018.pdf?10000 in Firefox, zoomed ~800%

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:62.0) Gecko/20100101 Firefox/62.0
Build ID: 20180830143136

Steps to reproduce:

Steps to reproduce:

1. Open a PDF in Firefox

2. Zoom in to 1000% (the maximum, so the effect is best visible on this zoom level)
You should now see pixels, how big the pixels are depends on the PDF

3. Download the PDF (keep Firefox open)

4. Open the downloaded PDF with a PDF viewer that is installed on your computer (in my case Adobe Acrobat Viewer DC, but can be any other)

5. Zoom in on your PDF viewer to 1000% or higher, and compare


Actual results:

On the Firefox side, you see pixels where there should be none, because it are vectors (like in .svg files)
The comparing part is because there could always be pixels in the real file, e.g. in photos, but also badly designed things which could be done in vectors.


Expected results:

The vectors should be respected in PDFs in Firefox, like is also done in .svg files (.svg files look just fine if you zoom in)

Comment 1

[googoldinges]

Attachment: https://presspage-production-content.s3.amazonaws.com/uploads/570/spoorkaart-2018.pdf?10000 in Adobe Acrobat Reader DC, zoomed ~800%

Comment 2

[googoldinges]

Attachment: https://www.ns.nl/binaries/_ht_1527596744404/content/assets/ns-nl/dienstregeling/nieuwe-dienstregeling/ns-spoorkaart-met-treinseries.pdf in Firefox, zoom 1000%

Comment 3

[googoldinges]

Attachment: https://www.ns.nl/binaries/_ht_1527596744404/content/assets/ns-nl/dienstregeling/nieuwe-dienstregeling/ns-spoorkaart-met-treinseries.pdf in Adobe Acrobat Reader DC, zoom 1600%

Comment 4

[googoldinges]

Attachment: https://www.tandprothetiekbrabant.nl/wp-content/uploads/2016/12/DownloadPdf.pdf in Firefox, zoom 1000%

Comment 5

[googoldinges]

Attachment: https://www.tandprothetiekbrabant.nl/wp-content/uploads/2016/12/DownloadPdf.pdf in Adobe Acrobat Reader DC, zoom 2400%

Comment 6

[Brendan Dahl [:bdahl]]

We currently limit the size of the canvas that PDF.js creates. This means at a certain scale we just use CSS to achieve scaling instead of re-rendering. To fix this we'll need to implement a way of only drawing a portion of the viewport so we don't create giant canvases.

Comment 7

[Marco Castelluccio [:marco]]

Maybe doing this could help with https://github.com/mozilla/pdf.js/issues/2750, bug 1274502, bug 1269023.

Comment 8

[Marco Castelluccio [:marco]]

Doing this could also help with bug 1729199.

Comment 10

[Caspy7]

Post currently top of Firefox subreddit highlighting the poor comparison to Edge.
https://www.reddit.com/r/firefox/comments/12rtwri/why_does_edge_display_pdfs_better_than_firefox/

Comment 11

[Jules A [:AreYouAWiiizard]]

https://usa-oss.edifier.com/Uploads/images/2022/01/22/2022012211315516428223153470.pdf Is completely unreadable in Firefox but looks fine in Edge.

Comment 13

[miles.martin]

(In reply to Brendan Dahl [:bdahl] from comment #6)

We currently limit the size of the canvas that PDF.js creates. This means at
a certain scale we just use CSS to achieve scaling instead of re-rendering.
To fix this we'll need to implement a way of only drawing a portion of the
viewport so we don't create giant canvases.

In the meantime, would it be possible to implement an about:config flag to increase the size of the canvas for PDF.js? This would be hugely valuable for users less concerned with performance constraints and more interested in not having to switch applications for workflow.

Also, here is one additional URL that renders very poorly in PDF.js compared to other PDF renderers: https://www.vanshnookenraggen.com/_index/docs/NYC_full_trackmap.pdf

Comment 14

[Marco Castelluccio [:marco]]

https://github.com/mozilla/pdf.js/pull/17837 should help this by increasing the maximum size.

Comment 16

[Lukas]

Finally that problem will be addressed?! As hint: it is not only on high zoom levels, also on printing the PDF the blurry is visible, see 1863302

Comment 17

[Nicolò Ribaudo]

We are currently working on a fix that improves the quality on screen, but not when printing.

Comment 18

[Calixte Denizet (:calixte)]

Attachment: [mozilla/pdf.js] Render high-res partial page views when falling back to CSS zoom (bug 1492303) (#19128)

Comment 20

[Negritas Sergiu, Desktop QA]

Hello! I have managed to reproduce the issue with firefox 135.0a1(2025-01-01) on Ubuntu 22.04.

I can confirm that the issue is fixed with firefox 138.0a1(2025-03-20), 137.0b8 on Ubuntu 22.04, MacOS 15.2 and Windows 10, updating the flags accordingly and marking this issue as VERIFIED->FIXED.

Have a nice day!