Added a version of resize_image() that works inplace.

dlib/image_transforms/interpolation.h

@@ -1007,6 +1007,29 @@ namespace dlib
         resize_image(in_img, out_img, interpolate_bilinear());
     }
 
+// ----------------------------------------------------------------------------------------
+
+    template <
+        typename image_type
+        >
+    void resize_image (
+        double size_scale,
+        image_type& img 
+    )
+    {
+        // make sure requires clause is not broken
+        DLIB_ASSERT( size_scale > 0 ,
+            "\t void resize_image()"
+            << "\n\t Invalid inputs were given to this function."
+            << "\n\t size_scale:  " << size_scale
+            );
+
+        image_type temp;
+        set_image_size(temp, std::round(size_scale*num_rows(img)), std::round(size_scale*num_columns(img)));
+        resize_image(img, temp);
+        swap(img, temp);
+    }
+
 // ----------------------------------------------------------------------------------------
 
     template <

dlib/image_transforms/interpolation_abstract.h

@@ -414,6 +414,28 @@ namespace dlib
             - Uses the bilinear interpolation to perform the necessary pixel interpolation.
     !*/
 
+// ----------------------------------------------------------------------------------------
+
+    template <
+        typename image_type
+        >
+    void resize_image (
+        double size_scale,
+        image_type& img 
+    );
+    /*!
+        requires
+            - image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
+            - pixel_traits<typename image_traits<image_type>::pixel_type>::has_alpha == false
+        ensures
+            - Resizes img so that each of it's dimensions are size_scale times larger than img.
+              In particular, we will have:
+                - #img.nr() == std::round(size_scale*img.nr())
+                - #img.nc() == std::round(size_scale*img.nc())
+                - #img == a bilinearly interpolated copy of the input image.
+    !*/
+
 // ----------------------------------------------------------------------------------------
 
     template <