simplified SURF example program

examples/surf_ex.cpp

 // The contents of this file are in the public domain. See LICENSE_FOR_EXAMPLE_PROGRAMS.txt
 /*
 
-    This is a simple example illustrating the use of the get_surf_points()
-    function.  It pulls out the first 100 SURF points from an input image 
-    and displays them on the screen as an overlay on the image.
+    This is a simple example illustrating the use of the get_surf_points() function.  It
+    pulls out SURF points from an input image and displays them on the screen as an overlay
+    on the image.
 
-    For a description of the SURF algorithm you should consult the following
-    papers:
+    For a description of the SURF algorithm you should consult the following papers:
         This is the original paper which introduced the algorithm:
             SURF: Speeded Up Robust Features
             By Herbert Bay, Tinne Tuytelaars, and Luc Van Gool
@@ -18,7 +17,7 @@
 
 
 
-#include <dlib/gui_widgets.h>
+#include <dlib/image_keypoint/draw_surf_points.h>
 #include <dlib/image_io.h>
 #include <dlib/image_keypoint.h>
 #include <fstream>
@@ -40,53 +39,35 @@ int main(int argc, char** argv)
             return 1;
         }
 
-        // Here we declare an image object that can store rgb_pixels.  Note that in 
-        // dlib there is no explicit image object, just a 2D array and
-        // various pixel types.  
+        // Here we declare an image object that can store rgb_pixels.  Note that in dlib
+        // there is no explicit image object, just a 2D array and various pixel types.  
         array2d<rgb_pixel> img;
 
-        // Now load the image file into our image.  If something is wrong then
-        // load_image() will throw an exception.  Also, if you linked with libpng
-        // and libjpeg then load_image() can load PNG and JPEG files in addition
-        // to BMP files. 
+        // Now load the image file into our image.  If something is wrong then load_image()
+        // will throw an exception.  Also, if you linked with libpng and libjpeg then
+        // load_image() can load PNG and JPEG files in addition to BMP files. 
         load_image(img, argv[1]);
 
-        // get the 100 strongest SURF points from the image
-        std::vector<surf_point> sp = get_surf_points(img, 100);
+        // Get SURF points from the image.  Note that get_surf_points() has some optional
+        // arguments that allow you to control the number of points you get back.  Here we
+        // simply take the default.
+        std::vector<surf_point> sp = get_surf_points(img);
+        cout << "number of SURF points found: "<< sp.size() << endl;
 
-        // create a window to display the input image and the SURF boxes.  (Note that
-        // you can zoom into the window by holding CTRL and scrolling the mouse wheel)
-        image_window my_window(img);
-
-        // Now lets draw some rectangles on top of the image so we can see where
-        // SURF found its points.
-        for (unsigned long i = 0; i < sp.size(); ++i)
+        if (sp.size() > 0)
         {
-            // Pull out the info from the SURF point relevant to figuring out
-            // where its rotated box should be.  This is the box it extracted 
-            // the SURF descriptor vector from.
-            const unsigned long box_size = static_cast<unsigned long>(sp[i].p.scale*20);
-            const double ang = sp[i].angle;
-            const point center(sp[i].p.center);
-            const rectangle rect = centered_rect(center, box_size, box_size); 
-
-            // Rotate the 4 corners of the rectangle 
-            const point p1 = rotate_point(center, rect.tl_corner(), ang);
-            const point p2 = rotate_point(center, rect.tr_corner(), ang);
-            const point p3 = rotate_point(center, rect.bl_corner(), ang);
-            const point p4 = rotate_point(center, rect.br_corner(), ang);
-
-            // Draw the sides of the box as red lines
-            my_window.add_overlay(p1, p2, rgb_pixel(255,0,0));
-            my_window.add_overlay(p1, p3, rgb_pixel(255,0,0));
-            my_window.add_overlay(p4, p2, rgb_pixel(255,0,0));
-            my_window.add_overlay(p4, p3, rgb_pixel(255,0,0));
-
-            // Draw a line from the center to the top side so we can see how the box is oriented.
-            // Also make this line green.
-            my_window.add_overlay(center, (p1+p2)/2, rgb_pixel(0,255,0));
+            // A surf_point object contains a lot of information describing each point.
+            // The most important fields are shown below:
+            cout << "center of first SURF point: "<< sp[0].p.center << endl;
+            cout << "pyramid scale:     " << sp[0].p.scale << endl;
+            cout << "SURF descriptor: \n" << sp[0].des << endl;
         }
 
+        // Create a window to display the input image and the SURF points.  (Note that
+        // you can zoom into the window by holding CTRL and scrolling the mouse wheel)
+        image_window my_window(img);
+        draw_surf_points(my_window, sp);
+
         // wait until the user closes the window before we let the program 
         // terminate.
         my_window.wait_until_closed();