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[gdal] Histogram: adjust bin count according to scale

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Fix #59461
This commit is contained in:
Alessandro Pasotti 2025-09-22 12:10:06 +02:00 committed by Nyall Dawson
parent 06e7f7e730
commit 5534cbed52
2 changed files with 33 additions and 3 deletions
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10
src/core/providers/gdal/qgsgdalprovider.cpp
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@ -2040,6 +2040,11 @@ QgsRasterHistogram QgsGdalProvider::histogram( int bandNo,
} }
} }
const double myScale { bandScale( bandNo ) };
// Adjust bin count according to scale
// Fix issue GH #59461
myHistogram.binCount = static_cast<int>( myHistogram.binCount * myScale );
if ( ( sourceHasNoDataValue( bandNo ) && !useSourceNoDataValue( bandNo ) ) || if ( ( sourceHasNoDataValue( bandNo ) && !useSourceNoDataValue( bandNo ) ) ||
!userNoDataValues( bandNo ).isEmpty() ) !userNoDataValues( bandNo ).isEmpty() )
{ {
@ -2092,9 +2097,8 @@ QgsRasterHistogram QgsGdalProvider::histogram( int bandNo,
double myMinVal = myHistogram.minimum; double myMinVal = myHistogram.minimum;
double myMaxVal = myHistogram.maximum; double myMaxVal = myHistogram.maximum;
// unapply scale anf offset for min and max // unapply scale and offset for min and max
double myScale = bandScale( bandNo ); const double myOffset = bandOffset( bandNo );
double myOffset = bandOffset( bandNo );
if ( myScale != 1.0 || myOffset != 0. ) if ( myScale != 1.0 || myOffset != 0. )
{ {
myMinVal = ( myHistogram.minimum - myOffset ) / myScale; myMinVal = ( myHistogram.minimum - myOffset ) / myScale;

26
tests/src/python/test_provider_gdal.py
View File

@ -550,6 +550,32 @@ class PyQgsGdalProvider(QgisTestCase, RasterProviderTestCase):
# This was triggering another crash: # This was triggering another crash:
self.assertEqual(rl.dataProvider().colorInterpretationName(1), "Undefined") self.assertEqual(rl.dataProvider().colorInterpretationName(1), "Undefined")
def testHistogramBinCountWithScale(self):
"""Test issue GH #59461"""
# Create raster with 2x2 pixels, int type, values 0-10000, scale 0.001
tmp_dir = QTemporaryDir()
tmpfile = os.path.join(tmp_dir.path(), "testBinCountWithScale.tif")
ds = gdal.GetDriverByName("GTiff").Create(tmpfile, 2, 2, 1, gdal.GDT_Int32)
ds.SetGeoTransform([0, 1, 0, 0, 0, -1])
ds.SetProjection("EPSG:4326")
ds.WriteRaster(0, 0, 2, 2, struct.pack("i" * 4, 0, 5000, 10000, -10000))
# Set band scale
band = ds.GetRasterBand(1)
band.SetScale(0.001)
ds = None
rl = QgsRasterLayer(tmpfile, "test")
self.assertTrue(rl.isValid())
provider = rl.dataProvider()
# Data type is changed by QGIS becase of the scale
self.assertEqual(provider.dataType(1), Qgis.DataType.Float32)
self.assertEqual(provider.bandScale(1), 0.001)
# Create histogram
hist = provider.histogram(1, 10000)
self.assertIsNotNone(hist)
self.assertEqual(hist.binCount, 10)
if __name__ == "__main__": if __name__ == "__main__":
unittest.main() unittest.main()