Question

I got school task again. This time, my teacher gave me task to create algorithm to count how many ducks on picture.

The picture is similar to this one:

I think I should use pattern recognition for searching how many ducks on it. But I don’t know which pattern match for each duck.

Answer 1

Here’s one way:

Hough transform for circles:

• Initialize an accumulator array indexed by (x,y,radius)
• For each pixel:
  • calculate an edge (e.g. Sobel operator will provide both magnitude and direction), if magnitude exceeds some threshold then:
    • increment every accumulator for which this edge could possibly lend evidence (only the (x,y) in the direction of the edge, only radii between min_duck_radius and max_duck_radius)
• Now smooth and threshold the accumulator array, and the coordinates of highest accumulators show you where the heads are. The threshold may leap out at you if you histogram the values in the accumulators (there may be a clear difference between “lots of evidence” and “noise”).

So that’s very terse, but it can get you started.