Displaying raster images extremely slow

[cdavila]

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

[cdavila]

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

[homann]

Let's check with 0.9.1 when it is released.

[homann]

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

[cdavila]

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.

[homann]

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

[cdavila]

I'm having the same problem again. Tested with versions r7994, r8009 and r8022 and in two different machines. Not with 0.9.1 packages.

[cdavilam]

The problem persists in r8223. 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.

[msieczka]

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"

[cdavilam]

Diff between revisions 7951 and 7952

[cdavilam]

After some investigation compiling various revisions, I have found this bug was introduced in r7952. I have attached diff between revisions 7951 and 7952. Log for r7952 is:

r7952 | ersts | 2008-01-14 04:48:11 +0100 (lun, 14 ene 2008) | 1 line

-Set default contrast enhancement to STRETCH_TO_MIN_MAX

[ersts]

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.

[(none)]

Milestone Version 0.9.2 deleted