Displaying a corner map

      #include <gandalf/vision/corner_disp.h>

There are functions to display both whole corner maps and individual corners, the latter being used, for instance, to highlight corners in a different colour. The functions invoke OpenGL routines, and the OpenGL display window must be set up beforehand. Also you will need to set up some colours as single precision floating point RGB pixel structures. We can use the colour structures set up for the edge detector in Section 5.7.3. Then an example call to display an corner map is

      /* display a whole corner map using OpenGL */
      gan_corner_feature_map_display ( &CornerMap, 0.0F /* displayed size of a corner */,
                                       NULL, /* affine transformation of coordinates */
                                       &red, /* corner colour */
                                       &green ); /* colour of bounding box */

The second argument is the size of the square box used to display each corner point. If it is passed as zero, as is the case here, a single point is drawn on the image. The third argument is an affine transformation of coordinates that allows additional freedom in positioning and scaling the corner map on the display window.vision_test.c has some example code using this routine.

To highlight a single corner, use instead

      Gan_CornerFeature *pCorner;

      /* ... set pCorner to point to a Gan_CornerFeature structure ... */

      /* display a single corner using OpenGL */
      gan_corner_feature_display ( pCorner, 0.0F /* displayed size of each corner */,
                                   NULL, /* affine transformation of coordinates */
                                   &yellow ); /* colour to highlight corner */

Note that the NULL passed for the affine coordinate transformation indicates an identity transformation.