find the circularity of diamond, inverted triangle and octagon shape

hi,currently I working with road sign sign detection, based on the observations from regionprops of matlab value, to detect circular shape, the circularities should be < 1.2, for square shape, circularities <1.6 and triangle shape should be <1.8

Can I know what is the circularities values for diamond , inverted triangle and octagon shapes respectively?

Answer 1

[Image Analyst]

Circularity is obtained by solving for the radius in terms of both the perimeter and area for a circle:

P = 2*pi*r
r = P/(2*pi)

A = pi*r^2
r = sqrt(A/pi) = P/(2*pi)

A/pi = P^2 / (4*pi^2)
1 = p^2 / (4*pi*A) = circularity

circularity = Perimeter^2 / (4 * pi * Area)

To find out what it is for those shapes, just create those shapes, and measure the perimeter and area.

[Tulips]

for octagon and diamond shape , to calculate the circularity , should I know their area?how to find the area of diamond and octagon shapes?

[Image Analyst]

Haven't you seen my Image Segmentation Tutorial? It goes over all of that.