low-level

Question 1

How does flood-fill labelling work?

Answer 1

Scan along image until foreground region is found, then, each connected foreground pixel above and to the left is given the same label.

do this over the whole image, giving each new region a new label

Question 2

When is an equivalence table used in labelling?

Answer 2

With like a U shape - since theres a gap between the two sticks. So it will not consider them connected till it gets to the bottom (at which point it will add all connected pixels to an equivalence table)

Then a second pass is done to make all equivalent regions the same label

Question 3

What are 8 ways of describing a region?

Answer 3

Area

Changes in direction of boundary

Length of boundary

Bounding box

Circularity (Closeness of C^2/A to 4Pi)

Rectangularity (whether A/wh <= 1)

Shape descriptor (extremal points)

Number of holes

Question 4

What does hough transform do?

Answer 4

Describes line-based features in an image, specifically curves such as lines, circles and ellipses