fix cell statistics median method and add tests

qgis · Nov 7, 2020 · dcc26ee · dcc26ee
1 parent 25d3b95
commit dcc26ee
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Showing 3 changed files with 16 additions and 5 deletions.
diff --git a/src/analysis/processing/qgsrasteranalysisutils.cpp b/src/analysis/processing/qgsrasteranalysisutils.cpp
@@ -329,14 +329,14 @@ double QgsRasterAnalysisUtils::meanFromCellValues( std::vector<double> cellValue
 double QgsRasterAnalysisUtils::medianFromCellValues( std::vector<double> cellValues, int stackSize )
 {
   std::sort( cellValues.begin(), cellValues.end() );
-  int medianElementIdx = stackSize / 2;
-  if ( stackSize % 2 == 0 )
+  bool even = ( stackSize % 2 ) < 1;
+  if ( even )
   {
-    return ( cellValues[medianElementIdx] + cellValues[medianElementIdx + 1] ) / 2.0;
+    return ( cellValues[stackSize / 2 - 1] + cellValues[stackSize / 2] ) / 2.0;
   }
-  else
+  else //odd
   {
-    return cellValues[medianElementIdx];
+    return cellValues[( stackSize + 1 ) / 2 - 1];
   }
 }
 

diff --git a/tests/src/analysis/testqgsprocessingalgs.cpp b/tests/src/analysis/testqgsprocessingalgs.cpp
@@ -2298,6 +2298,17 @@ void TestQgsProcessingAlgs::cellStatistics_data()
       << QStringLiteral( "/cellstatistics_variance_result_float32.tif" )
       << Qgis::Float32;
 
+  /*
+   * Testcase 17: median with even number of layers
+   */
+  QTest::newRow( "testcase_17" )
+      << QStringList( {"/raster/statisticsRas1_float64.asc", "/raster/statisticsRas1_float64.asc", "/raster/statisticsRas2_float64.asc", "/raster/statisticsRas3_float64.asc"} )
+      << QStringLiteral( "/raster/statisticsRas1_float64.asc" )
+      << 3
+      << false
+      << QStringLiteral( "/cellstatistics_median_result_fourLayers.tif" )
+      << Qgis::Float64;
+
 }
 
 void TestQgsProcessingAlgs::cellStatistics()

diff --git a/...stdata/control_images/expected_cellStatistics/cellstatistics_median_result_fourLayers.tif b/...stdata/control_images/expected_cellStatistics/cellstatistics_median_result_fourLayers.tif