Processing: GDAL Proximity - incorrect result if "Values" is not filled

[qgib]

Author Name: Filipe Dias (@fsdias)
Original Redmine Issue: 14115
Affected QGIS version: 2.12.2
Redmine category:processing/gdal
Assignee: Victor Olaya

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Rasterize (GDAL Rasterize) the attached shapefile using ID as value

Run Proximity with the resulting raster

Output raster has the same value in every pixel

Proximity grid from SAGA GIS works as expected and generates a raster with distances.

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• roads.zip (Filipe Dias)

[qgib]

Author Name: Filipe Dias (@fsdias)

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• 9472 was configured as roads.zip

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• roads.zip (Filipe Dias)

[qgib]

Author Name: Alexander Bruy (@alexbruy)

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Running gdal_proximity.py from command line gives same result, so seems this is GDAL issue not Processing. Please submit ticket to GDAL track.

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• resolution was changed from to up/downstream
• status_id was changed from Open to Rejected

[qgib]

Author Name: Filipe Dias (@fsdias)

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Alexander, thanks for testing.

I filled "Values" with 10 (the ID value with which the roads raster was created) and it worked as expected.

It seems the algorithm needs the user to fill it with the appropriate value. Does this still qualify as a GDAL bug?

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• subject was changed from Processing: GDAL Proximity appears to be broken to Processing: GDAL Proximity - incorrect result if "Values" is not filled

[qgib]

Author Name: Alexander Bruy (@alexbruy)

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With passed "Values" it produces correct result. I still think that this is GDAL bug, as from documentation, "values" is

A list of target pixel values in the source image to be considered target pixels. If not specified, all non-zero pixels will be considered target pixels.

Maybe it takes in account also NODATA values

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• status_id was changed from Rejected to Feedback
• resolution was changed from up/downstream to

[qgib]

Author Name: Giovanni Manghi (@gioman)

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I really don't see anything wrong here. GDAL expects a list of values and so (of course) does QGIS. If not provided it uses all non zero pixels. Someone could argue about nulls, but that must be done in the gdal tracker.

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