Displaying raster images extremely slow

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Author Name: cdavila - (cdavila -)
Original Redmine Issue: 778

Redmine category:rasters
Assignee: Magnus Homann

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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

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• diff_7951_vs_7952 (cdavilam -)

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Author Name: cdavila - (cdavila -)

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

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Author Name: Magnus Homann (@homann)

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Let's check with 0.9.1 when it is released.

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• status_id was changed from Open to In Progress

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Author Name: Magnus Homann (@homann)

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

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Author Name: cdavila - (cdavila -)

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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.

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Author Name: Magnus Homann (@homann)

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

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• resolution was changed from to fixed
• status_id was changed from In Progress to Closed

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Author Name: cdavila - (cdavila -)

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I'm having the same problem again. Tested with versions d011ea4 (SVN r7995), 23386bd (SVN r8010) and 34acd76 (SVN r8023) and in two different machines. Not with 0.9.1 packages.

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• status_id was changed from Closed to Feedback
• resolution was changed from fixed to

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Author Name: cdavilam - (cdavilam -)

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The problem persists in 44cc122 (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.

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Author Name: Maciej Sieczka - (Maciej Sieczka -)

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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"

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Author Name: cdavilam - (cdavilam -)

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After some investigation compiling various revisions, I have found this bug was introduced in 4c31165 (SVN r7953). I have attached diff between revisions 7951 and 7952. Log for 4c31165 (SVN r7953) is:

4c31165 (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

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Author Name: ersts - (ersts -)

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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.

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• status_id was changed from Feedback to Closed
• resolution was changed from to fixed

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Author Name: Anónimo (Anónimo)

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Milestone Version 0.9.2 deleted