Bug report #778

Displaying raster images extremely slow

Added by cdavila - over 15 years ago. Updated almost 14 years ago.

Assignee:Magnus Homann
Affected QGIS version: Regression?:No
Operating System:Debian Easy fix?:No
Pull Request or Patch supplied: Resolution:fixed
Crashes QGIS or corrupts data: Copied to github as #:10837


After updating from 0.8.1 to 0.9 ecw rester images that before were displayed at once now take very long time: 4 images of 9 MB each one take about 8 minutes and images of about 700 MB don't display after one hour.
More information can be found here: http://forum.qgis.org/viewtopic.php?t=461
Reproduced in two machines with debian-testing and reported by other user in windows XP

diff_7951_vs_7952 - Diff between revisions 7951 and 7952 (2.5 KB) cdavilam -, 2008-04-01 12:29 PM


#1 Updated by cdavila - over 15 years ago

I have just replace 0.9.0 package with 0.9~svn20071023-1 from debian.gfoss.it and the problem has disappeared.

#2 Updated by Magnus Homann over 15 years ago

  • Status changed from Open to In Progress

Let's check with 0.9.1 when it is released.

#3 Updated by Magnus Homann over 15 years ago

0.9.1 is now released. I believe this error has disappeared. Can you check?

#4 Updated by cdavila - over 15 years ago

I'm still not using definitive 0.9.1, but 0.9.1~pre20071219 from debian.gfoss.it, but problem has certainly disappeared, so I think bug can be closed if no one has same problem.

#5 Updated by Magnus Homann over 15 years ago

  • Resolution set to fixed
  • Status changed from In Progress to Closed

I also noted slow performance on 0.9.0, but not anymore.

#6 Updated by cdavila - over 15 years ago

  • Status changed from Closed to Feedback
  • Resolution deleted (fixed)

I'm having the same problem again. Tested with versions d011ea48 (SVN r7995), 23386bd0 (SVN r8010) and 34acd76b (SVN r8023) and in two different machines. Not with 0.9.1 packages.

#7 Updated by cdavilam - about 15 years ago

The problem persists in 44cc1223 (SVN r8224). Now a bug squashing is being planned, I would really appreciate if this bug is resolved, as I need to use ecw rasters in my daily work and it's really annoying to wait so much time each time I move map canvas, having to use other programs too often.

#8 Updated by Maciej Sieczka - about 15 years ago

I'm not sure if this is relevant, but in general QGIS is very slow displaying tiled GeoTIFFs. Stripped GeoTIFFs display about 10 (ten) times faster.

Stripped GeoTIFF can be created with:

gdal_translate -co "TILED=NO" 

and a tiled one with:

gdal_translate -co "TILED=YES" 

#9 Updated by cdavilam - about 15 years ago

After some investigation compiling various revisions, I have found this bug was introduced in 4c31165e (SVN r7953). I have attached diff between revisions 7951 and 7952. Log for 4c31165e (SVN r7953) is:

4c31165e (SVN r7953) | ersts | 2008-01-14 04:48:11 +0100 (lun, 14 ene 2008) | 1 line

-Set default contrast enhancement to STRETCH_TO_MIN_MAX

#10 Updated by ersts - about 15 years ago

  • Status changed from Feedback to Closed
  • Resolution set to fixed

There is now an ability to set the default contrast enhancement that will remain persistent between sessions, which resolves this problem to some extent. If stretching is too slow and not needed, the user can elect not to stretch on initial load.

I think this closes this ticket for QGIS, if there are any upstream issues with GDAL that are also fixed in the future, all the more better.

If this is still not a satisfactory solution, feel free to reopen.

#11 Updated by Anonymous almost 14 years ago

Milestone Version 0.9.2 deleted

Also available in: Atom PDF