PDF.js, resolution of rendered image




PDF Viewer
5 years ago
5 years ago


(Reporter: Mel Turner, Unassigned)


20 Branch
Mac OS X

Firefox Tracking Flags

(Not tracked)


(Whiteboard: [pdfjs-c-performance])


(3 attachments)



5 years ago
Created attachment 751497 [details]

User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_8_3) AppleWebKit/536.29.13 (KHTML, like Gecko) Version/6.0.4 Safari/536.29.13

Steps to reproduce:

I am downloading single page PDF files which consist of a large page (48 x 65 cm) image prepared in ABBYY Finereader as text under image.

Actual results:

The document is rendered correctly but needs to be magnified by at least 400% to read the text. The rendered image appears to be too low a resolution and when magnified is not readable.

Expected results:

The embedded image is of sufficient resolution and renders properly in Safari/Preview or Acrobat. 

Attached is a subject PDF. The download facility can be viewed at http://mvtm.ca/museum/?page_id=2759
Component: General → PDF Viewer
Product: Core → Firefox
At 100% zoom this pdf looks the same in preview and Firefox to me.  Do you have a screenshot of the two compared side by side?
Flags: needinfo?(meljturner)
Priority: -- → P4
Whiteboard: [pdfjs-c-performance]

Comment 2

5 years ago
Created attachment 755498 [details]
screenshot, firefox
Flags: needinfo?(meljturner)

Comment 3

5 years ago
Created attachment 755500 [details]
screenshot, Safari

Comment 4

5 years ago
(In reply to Brendan Dahl from comment #1)
> At 100% zoom this pdf looks the same in preview and Firefox to me.  Do you
> have a screenshot of the two compared side by side?

The two attachments are firefox and safari respectively at about 350% zoom. At 100% zoom the problem is not apparent. I appears that firefox zooms by magnifying the 100% zoom rather than by resampling the downloaded image.

Comment 5

5 years ago
My attachments got deleted, not sure why!?
Mozilla/5.0 (Macintosh; Intel Mac OS X 10.7; rv:26.0) Gecko/20100101 Firefox/26.0
Using latest Nightly (20130917030214), the document at 400% zoom looks very much alike with the one provided by Safari.

Could you please try too and confirm? The Nightly build is available at: http://nightly.mozilla.org/
Flags: needinfo?(meljturner)

Comment 7

5 years ago
Using Firefox Nightly (2013-09-17) this problem appears to be resolved. Thank you very much.

Note the onscreen magnification menu only allows selection of up to 200%, but using the '+' I increased the magnification to 350% and the resolution remained clear.

Note the original url that illustrated the problem has changed. Now at http://mvtm.ca/mvtm/?page_id=2759
Last Resolved: 5 years ago
Flags: needinfo?(meljturner)
Resolution: --- → WORKSFORME
Thank you for your answer.

Indeed zoom picker only allows up to 200% zoom, but for zoom in/out the +/- buttons or the Command+/Command- or Command + mouse scroll can also be used.
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