- How could the
Hough transform method be used to detect circles of radius 10 units?
Show that pixels in (
*x*,*y*) space would map to circles in this case if Eqn. 8 is used to define circles. - Suppose the Hough transform method is to be used to
detect circles of arbitrary radius. What would pixels in (
*x*,*y*) space now map to? How much less efficient would it be to search for arbitrary circles than circles of a fixed radius? - We can represent the equation of a circle parametrically by

How you could implement a Hough Transform to detect circles using this form of equation? Comment on this methods relative merits / drawbacks.

- How would you use the Hough transform to detect
- an ellipse
- a hexagon.

- How would you use the Hough transform to detect three-dimensional shapes (in depth maps). In particular how would detect three-dimensional straight lines.
- Write a C or PASCAL type procedure to detect straight lines only in an image using the Hough transform algorithm.
- Draw some simple objects and work out their extended Gaussian images.
- Give some examples of sets of objects that have the same extended Gaussian image (see Fig. 54).

dave@cs.cf.ac.uk