DOC: enhance documentation on confidence maps

Modules/Applications/AppClassification/app/otbImageClassifier.cxx

@@ -96,7 +96,17 @@ private:
     SetParameterOutputImagePixelType( "out", ImagePixelType_uint8);
 
     AddParameter(ParameterType_OutputImage, "confmap",  "Confidence map");
-    SetParameterDescription( "confmap", "Confidence map of the produced classification. Meaning depends on the model.");
+    SetParameterDescription( "confmap", "Confidence map of the produced classification. The confidence index depends on the model : \n"
+      "  - LibSVM : difference between the two highest probabilities (needs a model with probability estimates, so that classes probabilities can be computed for each sample)\n"
+      "  - OpenCV\n"
+      "    * Boost : sum of votes\n"
+      "    * DecisionTree : (not supported)\n"
+      "    * GradientBoostedTree : (not supported)\n"
+      "    * KNearestNeighbors : number of neighbors with the same label\n"
+      "    * NeuralNetwork : difference between the two highest responses\n"
+      "    * NormalBayes : (not supported)\n"
+      "    * RandomForest : proportion of decision trees that classified the sample to the second class (only works for 2-class models)\n"
+      "    * SVM : distance to margin (only works for 2-class models)\n");
     SetParameterOutputImagePixelType( "confmap", ImagePixelType_double);
     MandatoryOff("confmap");