Added set_rect_area()

dlib/geometry/drectangle.h

@@ -441,6 +441,30 @@ namespace dlib
         return shrink_rect(rect, -width, -height);
     }
 
+    inline drectangle set_rect_area (
+        const drectangle& rect,
+        double area
+    )
+    {
+        DLIB_ASSERT(area >= 0, "drectangle can't have a negative area.");
+
+        if (area == 0)
+            return drectangle(dcenter(rect));
+
+        if (rect.area() == 0)
+        {
+            // In this case we will make the output rectangle a square with the requested
+            // area.
+            double scale = std::sqrt(area);
+            return centered_drect(rect, scale, scale);
+        }
+        else
+        {
+            double scale = std::sqrt(area/rect.area());
+            return centered_drect(rect, rect.width()*scale, rect.height()*scale);
+        }
+    }
+
     inline drectangle set_aspect_ratio (
         const drectangle& rect,
         double ratio

dlib/geometry/drectangle_abstract.h

@@ -585,6 +585,23 @@ namespace dlib
               (i.e. grows the given drectangle by expanding its border)
     !*/
 
+// ----------------------------------------------------------------------------------------
+
+    drectangle set_rect_area (
+        const drectangle& rect,
+        double area
+    );
+    /*!
+        requires
+            - area >= 0
+        ensures
+            - Returns a rectangle R such that:
+                - center(R) == center(rect)
+                - R has the same aspect ratio as rect.  If rect.area() == 0 then the
+                  returned rect has a 1:1 aspect ratio.
+                - R.area() == area
+    !*/
+
 // ----------------------------------------------------------------------------------------
 
     drectangle set_aspect_ratio (

dlib/geometry/rectangle.h

@@ -726,6 +726,29 @@ namespace dlib
         return rectangle(x, y, x+rect.width()-1, y+rect.height()-1);
     }
 
+// ----------------------------------------------------------------------------------------
+
+    inline rectangle set_rect_area (
+        const rectangle& rect,
+        unsigned long area
+    )
+    {
+        DLIB_ASSERT(area > 0);
+
+        if (rect.area() == 0)
+        {
+            // In this case we will make the output rectangle a square with the requested
+            // area.
+            unsigned long scale = std::round(std::sqrt(area));
+            return centered_rect(rect, scale, scale);
+        }
+        else
+        {
+            double scale = std::sqrt(area/(double)rect.area());
+            return centered_rect(rect, (long)std::round(rect.width()*scale), (long)std::round(rect.height()*scale));
+        }
+    }
+
 // ----------------------------------------------------------------------------------------
 
     inline rectangle set_aspect_ratio (

dlib/geometry/rectangle_abstract.h

@@ -487,6 +487,23 @@ namespace dlib
               and height)
     !*/
 
+// ----------------------------------------------------------------------------------------
+
+    inline rectangle set_rect_area (
+        const rectangle& rect,
+        unsigned long area
+    );
+    /*!
+        requires
+            - area > 0
+        ensures
+            - Returns a rectangle R such that:
+                - center(R) == center(rect)
+                - R has the same aspect ratio as rect.  If rect.area() == 0 then the
+                  returned rect has a 1:1 aspect ratio.
+                - R.area() == area
+    !*/
+
 // ----------------------------------------------------------------------------------------
 
     inline rectangle set_aspect_ratio (