What is the underlying principle of the Moravec corner detector?

- moving away from a corner introduces a small change
moving away from a corner introduces a large change

- moving away from a uniform region introduces a large change
- moving along an edge introduces a large change

The first stage of the Canny edge detector involves smoothing with what?

a Gaussian

- a 3 x 3 blur mask
- a Laplacean mask
- a Sobel mask

Which of the following transformations is not handled by SIFT?

- contrast changes
reflections

- scale changes
- rotations

Which of the following is

*not*an underlying principle of the Canny edge detector?- edges should be located in the correct place
- all edges should be found
a broad edge should produce a response at both sides

- it should respond only to edges

The Canny edge detector represents more or less the state of the art in detecting edges in images. Why is its output still of limited use?

- the edges are still too noisy to be useful
- it doesn't find all edges
edges are of limited value in practice

- it is too slow

Which of the following schemes is unsuitable for matching arbitrary features in images?

- image differencing
the Laplacean

- cross-correlation
- matched filtering

Which of the following is NOT suitable for detecting corners?

SIFT

- Harris and Stephens
- FAST
- Moravec

What information does the Canny edge detector find about each piece of edge?

- the direction
the magnitude and direction

- the magnitude, direction and width
- the magnitude

Which of the following is suitable for matching SIFT features P and Q?

- the expression sqrt{ P(x,y) } - sqrt{ Q(x, y) }
the expression sqrt{ (P(x,y) - Q(x, y))^2}

- the expression sqrt{ P(x,y)^2 + Q(x, y)^2 }
- the expression P(x,y) x Q(x, y)

Why does the Canny edge detector perform non-maximum suppression?

- to stop the edges being maxima
- to quantise the direction of the edge
to make each edge only one pixel wide

- to stop the edges being too bright