Adding a new example program for the SURF algorithm.

--HG--
extra : convert_revision : svn%3Afdd8eb12-d10e-0410-9acb-85c331704f74/trunk%403052

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 pull out the first 100 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:
+        This is the original paper which introduced the algorithm:
+            SURF: Speeded Up Robust Features
+            By Herbert Bay, Tinne Tuytelaars, and Luc Van Gool
+
+        This paper provides a nice detailed overview of how the algorithm works:
+            Notes on the OpenSURF Library by Christopher Evans
+
+*/
+
+
+
+#include "dlib/gui_widgets.h"
+#include "dlib/image_io.h"
+#include "dlib/image_keypoint.h"
+#include <fstream>
+
+
+using namespace std;
+using namespace dlib;
+
+//  ----------------------------------------------------------------------------
+
+int main(int argc, char** argv)
+{
+    try
+    {
+        // make sure the user entered an argument to this program
+        if (argc != 2)
+        {
+            cout << "error, you have to enter a BMP file as an argument to this program" << endl;
+            return 1;
+        }
+
+        // Here we open the image file.  Note that when you open a binary file with 
+        // the C++ ifstream you must supply the ios::binary flag.
+        ifstream fin(argv[1],ios::binary);
+        if (!fin)
+        {
+            cout << "error, can't find " << argv[1] << endl;
+            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.  
+        array2d<rgb_pixel>::kernel_1a img;
+
+        // now load the bmp file into our image.  If the file isn't really a BMP
+        // or is corrupted then load_bmp() will throw an exception.
+        load_bmp(img, fin);
+
+        // get the 100 strongest SURF points from the image
+        std::vector<surf_point> sp = get_surf_points(img, 100);
+
+        // create a window to display the input image and the SURF boxes
+        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)
+        {
+            // Pull out the info from the SURF point relevant to figuring out
+            // where its rotated box should be.
+            const double box_size = sp[i].p.scale*10;
+            const double ang = sp[i].angle;
+            const point center(sp[i].p.center);
+            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(image_window::overlay_line(p1, p2, rgb_pixel(255,0,0)));
+            my_window.add_overlay(image_window::overlay_line(p1, p3, rgb_pixel(255,0,0)));
+            my_window.add_overlay(image_window::overlay_line(p4, p2, rgb_pixel(255,0,0)));
+            my_window.add_overlay(image_window::overlay_line(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(image_window::overlay_line(center, (p1+p2)/2, rgb_pixel(0,255,0)));
+        }
+
+        // wait until the user closes the window before we let the program 
+        // terminate.
+        my_window.wait_until_closed();
+    }
+    catch (exception& e)
+    {
+        cout << "exception thrown: " << e.what() << endl;
+    }
+}
+
+//  ----------------------------------------------------------------------------
+