Bug 349863

Summary:	Support DJVU tiled rendering
Product:	[Applications] okular	Reporter:	Rafael Linux User <rafael.linux.user>
Component:	DjVu backend	Assignee:	Okular developers <okular-devel>
Status:	CONFIRMED ---
Severity:	major	CC:	aacid, rafael.linux.user
Priority:	NOR
Version First Reported In:	0.22.2
Target Milestone:	---
Platform:	openSUSE
OS:	Linux
Latest Commit:		Version Fixed In:
Sentry Crash Report:

Description Rafael Linux User 2015-07-03 14:18:29 UTC

In general, when I try to zoom a DjVu image, Okular shows only a white background instead continuing zooming the image. The zoom level is distinct in each DjVu document.
You can download this DjVu image http://www.tr3s60.com/Reproduccion_Ampliada/Zaragoza_1861_djvu/AMZ_4-2_0274.djvu
and enlarge it in Okular till you reach 50% level. Then you will see a white background, not the image.

Reproducible: Always

Steps to Reproduce:
1.Open a DjVu image
2.Zoom in it till you see no image

Actual Results:  
Okular is showing a white background instead of the image.

Expected Results:  
To continue enlarging the image.

For researchers, this is an important feature, cause they need to see fine details in old documents digitized in DjVu.

DjVuLibre (DjView) enlarge the referenced document as far as 1200% level.

Comment 1 Albert Astals Cid 2015-07-09 21:56:13 UTC

The problem is that we don't support tiled rendering for djvu files, i.e. we always render the whole page, and that means that we pass the "safety limit" net of size for a single page when zooming too much.

I'll increase the safety limits since they are quite small for nowadays standards and that will allow for some more zooming but the real fix is supporting the tiled rendering like we do for pdf files.

Comment 2 Rafael Linux User 2015-07-10 09:55:35 UTC

I understand, so I'll be waiting for the size limit change. But, what's the problem about implementing tile rendering on DjVu files? Is about complexity of the format? Is not usefull the open source code of DjView to embed that functionallity in Okular?

Thank you

Comment 3 Albert Astals Cid 2015-07-10 10:39:53 UTC

It's not hard, just need someone with time to do it.

Comment 4 Rafael Linux User 2015-07-10 10:52:09 UTC

Ok, I'm sure it will be a great improvement for Okular users that will not need to install DjView in the future.

;)

Comment 5 Justin Zobel 2021-03-09 23:59:26 UTC

Thank you for the bug report.

As this report hasn't seen any changes in 5 years or more, we ask if you can please confirm that the issue still persists.

If this bug is no longer persisting or relevant please change the status to resolved.

Comment 6 Rafael Linux User 2021-03-11 05:48:45 UTC

Issue still persist, despite it appears now from 151% 

https://www.zaragoza.es/imagenes_archivo/cartografia/AMZ_4-2_0274/AMZ_4-2_0274.djvu