Fix the medium value of the colorbar preview

AMAPVox/AMAPVoxVisualization/src/main/java/fr/amap/lidar/amapvox/visualization/views/MainView.java

@@ -27,6 +27,7 @@ package fr.amap.lidar.amapvox.visualization.views;
 import fr.amap.commons.util.swing.FrameView;
 import java.awt.BorderLayout;
 import java.awt.Frame;
+import java.util.function.Consumer;
 import javax.swing.JOptionPane;
 import javax.swing.WindowConstants;
 import net.jcip.annotations.GuardedBy;
@@ -143,26 +144,19 @@ public class MainView extends FrameView {
         /* Init the properties component */
         propertiesView = new PropertiesView();
         propertiesView.setParentView(this);
-        propertiesView.setOnChangePropertyCallback((name) -> {
-            if (scene != null) {
-                final Vector2f minAndMax = scene.getVoxelSpaceComponent().getMinAndMaxPropertyValues();
-                final float min = minAndMax.x;
-                final float max = minAndMax.y;
-                final float medium = (max - min) / 2;
-                viewView.setGradientTexts(Float.toString(min),
-                        Float.toString(medium), Float.toString(max));
-            }
-        });
-        propertiesView.setOnChangeMinAndMaxCallback((name) -> {
+        
+        final Consumer callback = (object) -> {
             if (scene != null) {
                 final Vector2f minAndMax = scene.getVoxelSpaceComponent().getMinAndMaxPropertyValues();
                 final float min = minAndMax.x;
                 final float max = minAndMax.y;
-                final float medium = (max - min) / 2;
+                final float medium = min + (max - min) / 2;
                 viewView.setGradientTexts(Float.toString(min),
                         Float.toString(medium), Float.toString(max));
             }
-        });
+        };
+        propertiesView.setOnChangePropertyCallback(callback);
+        propertiesView.setOnChangeMinAndMaxCallback(callback);
         getContentPane().add(propertiesView.getContentPane(), BorderLayout.WEST);
 
         /* Init the options component */