Bug report #3807: QgsRasterLayer.identify() is always True - QGIS Application - QGIS Issue Tracking

Bug report #3807

QgsRasterLayer.identify() is always True

Added by Ricardo Silva over 13 years ago. Updated over 5 years ago.

Status:	Closed
Priority:	Low
Assignee:	-
Category:	Rasters
Affected QGIS version:	master	Regression?:	No
Operating System:		Easy fix?:	No
Pull Request or Patch supplied:	No	Resolution:	end of life
Crashes QGIS or corrupts data:	No	Copied to github as #:	13865

Description

Using the python bindings, when trying to identify a point outside of current raster layer, The QgsRasterLayer.identify() method is returning:

(True, {PyQt4.QtCore.QString(u'Band 1'): PyQt4.QtCore.QString(u'out of extent')})

which doesn't make much sense IMO. If the result is the "out of extent" string, then the identifying has failed, so the first entry of the tuple should be False, instead of True.

History

#1 Updated by Ricardo Silva over 13 years ago

This is always true if the identified point is inside the extents of the raster layer, but in an area that is not part of the layer itself, in which case QgsRasterLayer.identify() returns:

(True, {PyQt4.QtCore.QString(u'Band 1'): PyQt4.QtCore.QString(u'null (no data)')})

I guess this is not intended behavior as well, because the tuple's first value is always True.

#2 Updated by Borys Jurgiel about 12 years ago

Affected QGIS version set to master
Crashes QGIS or corrupts data set to No
Pull Request or Patch supplied set to No
Assignee deleted (~~Borys Jurgiel~~)

#3 Updated by Jürgen Fischer over 10 years ago

Target version changed from Version 2.0.0 to Future Release - Lower Priority

#4 Updated by Médéric RIBREUX almost 9 years ago

Category changed from Python plugins to Rasters
Tag set to easy
Operating System deleted (~~Debian~~)

Hello, bug triage...

this is still true in QGIS 2.13 even if the identification mechanism have changed. Today, we use identify method on the raster layer provider:

ident = rlayer.dataProvider().identify(QgsPoint(15.30, 40.98), QgsRaster.IdentifyFormatValue)
if ident.isValid()
  ident.results()

# When you are out of the raster extent, ident is valid but the results are: {1:None}

We need to make identify method returns a non valid QgsRasterIdentifyResult when identification is outside the extent of the raster. Currently, when you look at the code, when we are outside of the extent, QGIS still returns a valid QgsRasterIdentifyResult with a QVariant for each band of the raster. I think this is easy to fix as long as this does not break something else.