Why does the last stage of the Canny edge detector perform hysteresis thresholding?

to connect together edge segments

- to reduce the effects of noise
- to make edge segments only one pixel wide
- to make the output image binary

Why does the last stage of the Canny edge detector employ two thresholds?

- not all edges produce a response between both thresholds
- not all edges produce a response below both thresholds
- to reduce the amount of noise in an image
not all edges produce a response above both thresholds

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

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

- to stop the edges being maxima

Which of the following transformations is not handled by SIFT?

reflections

- contrast changes
- scale changes
- rotations

What is the underlying principle of the Moravec corner detector?

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

Which of the following is NOT suitable for detecting corners?

- FAST
- Harris and Stephens
SIFT

- Moravec

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

- matched filtering
- cross-correlation
the Laplacean

- image differencing

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

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

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

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

Which of the following is

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

- it should respond only to edges