Moved impossible_labeling_error to error.h

dlib/error.h

@@ -420,6 +420,27 @@ namespace dlib
         !*/
     };
 
+// ----------------------------------------------------------------------------------------
+
+    class impossible_labeling_error : public dlib::error 
+    { 
+        /*!
+            WHAT THIS OBJECT REPRESENTS
+                This is the exception thrown by code that trains object detectors (e.g.
+                structural_svm_object_detection_problem) when they detect that the set of
+                truth boxes given to the training algorithm contains some impossible to
+                obtain outputs.  
+                
+                This kind of problem can happen when the set of image positions scanned by
+                the underlying object detection method doesn't include the truth rectangle
+                as a possible output.  Another possibility is when two truth boxes are very
+                close together and hard coded non-max suppression logic would prevent two
+                boxes in such close proximity from being output.
+        !*/
+    public: 
+        impossible_labeling_error(const std::string& msg) : dlib::error(msg) {};
+    };
+
 // ----------------------------------------------------------------------------------------
 
 }

dlib/svm/structural_svm_object_detection_problem.h

@@ -15,14 +15,6 @@
 namespace dlib
 {
 
-// ----------------------------------------------------------------------------------------
-
-    class impossible_labeling_error : public dlib::error 
-    { 
-    public: 
-        impossible_labeling_error(const std::string& msg) : dlib::error(msg) {};
-    };
-
 // ----------------------------------------------------------------------------------------
 
     template <

dlib/svm/structural_svm_object_detection_problem_abstract.h

@@ -12,23 +12,6 @@
 namespace dlib
 {
 
-// ----------------------------------------------------------------------------------------
-
-    class impossible_labeling_error : public dlib::error 
-    { 
-        /*!
-            WHAT THIS OBJECT REPRESENTS
-                This is the exception thrown by the structural_svm_object_detection_problem
-                when it detects that the image_scanner_type it is working with is incapable
-                of representing the truth rectangles it has been asked to predict.  
-
-                This kind of problem can happen when the test_box_overlap object indicates
-                that two ground truth rectangles overlap and are therefore not allowed to
-                both be output at the same time.  Or alternatively, if there are not enough
-                detection templates to cover the variety of truth rectangle shapes.
-        !*/
-    };
-
 // ----------------------------------------------------------------------------------------
 
     template <