Wrong legends/ramps for rasters

[qgib]

Author Name: Giovanni Manghi (@gioman)
Original Redmine Issue: 4806
Affected QGIS version: master
Redmine category:rasters

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Steps:

• add the attached raster (is a DEM)

• calculate the "aspect" map with the terrain analysis tool or with the gdaldem tool

The min/max values of the output are

STATISTICS_MINIMUM=0
STATISTICS_MAXIMUM=359.87353515625

but the legend will show values as

-9.8
398.8

which do not make any sense (see attached screenshot)

Another example is if you reclassify (with the raster calculator) the same DEM to a map with just "0" and "1"

• (dem_clipped@1>300)*1 + (dem_clipped@1<=300)*0

the resulting map will show a legend with values as

0.3
1.4

that once again do not make any sense.

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• dem_clipped.tif (Giovanni Manghi)
• 26.png (Giovanni Manghi)
• dem_clipped.tif (Giovanni Manghi)

[qgib]

Author Name: Alexander Bruy (@alexbruy)

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Not reproducible here with latest qgis-dev (-37) from OSGeo4W under 32bit Windows XP Pro SP3. Also tested under 32bit Slackware 13.37 with latest master (4413a7d), GDAL 1.9.0 with same result — not reproducible.

[qgib]

Author Name: Giovanni Manghi (@gioman)

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Alexander Bruy wrote:

Not reproducible here with latest qgis-dev (-37) from OSGeo4W under 32bit Windows XP Pro SP3. Also tested under 32bit Slackware 13.37 with latest master (4413a7d), GDAL 1.9.0 with same result — not reproducible.

Hi Alexander, that's weird, I also tested qgis master on both Windows and Linux. Do you mean that you are getting legends with the expected values?

[qgib]

Author Name: Alexander Bruy (@alexbruy)

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Giovanni Manghi wrote:

Hi Alexander, that's weird, I also tested qgis master on both Windows and Linux. Do you mean that you are getting legends with the expected values?

Right, I get correct legend values. In case with reclassified DEM this is 0 and 1. In case with "aspect" analysis results this is 0.14579 and 360. Maybe this is because you use 64bit system?

[qgib]

Author Name: Giovanni Manghi (@gioman)

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Alexander Bruy wrote:

Giovanni Manghi wrote:

Hi Alexander, that's weird, I also tested qgis master on both Windows and Linux. Do you mean that you are getting legends with the expected values?

Right, I get correct legend values. In case with reclassified DEM this is 0 and 1. In case with "aspect" analysis results this is 0.14579 and 360. Maybe this is because you use 64bit system?

My Linux box is 64 bit but my Windows VM is 32 bit, so should be something else. But what?

[qgib]

Author Name: Paolo Cavallini (@pcav)

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Confirmed here on Debian unstable 64bit (values from -8 to +399)

[qgib]

Author Name: Giovanni Manghi (@gioman)

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But I'm sure I got the same also on a 32bit system...

[qgib]

Author Name: Giovanni Manghi (@gioman)

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loading the attached raster (dem_lipped.tif), without applying any particular color map, in the legend I see a "-32767-32768" that I also don't uderstand

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• 4185 was configured as dem_clipped.tif

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• dem_clipped.tif (Giovanni Manghi)

[qgib]

Author Name: Alexander Bruy (@alexbruy)

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Giovanni Manghi wrote:

loading the attached raster (dem_lipped.tif), without applying any particular color map, in the legend I see a "-32767-32768" that I also don't uderstand

Confirmed but only when contrast enhacement is "Not set" or "Clip to MinMax". In all other cases I get correct values.
After looking into code I found that legend values are gathered from QgsContrastEnhancement object, so if contrast enhacement is "Not set" there are no values found and defaults used.

[qgib]

Author Name: Paolo Cavallini (@pcav)

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• fixed_version_id was changed from Version 1.7.4 to Version 1.8.0

[qgib]

Author Name: Paolo Cavallini (@pcav)

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• fixed_version_id was changed from Version 1.8.0 to Version 2.0.0

[qgib]

Author Name: Giovanni Manghi (@gioman)

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This has been fixed in master.

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