How to show just the rectangles in an image?

Question

I was given this function:

import matplotlib.patches as mpatches

from skimage.measure import regionprops

import math

facteurforme = lambda r: (4 * math.pi * r.area) / (r.perimeter * r.perimeter)

circ = lambda r: (r.perimeter)/(r.equivalent_diameter)

I should complete the code to detect just the rectangles in image made of circles and rectangles and then put the detected shapes in a box using Python 3 .

I'd know how to use facteurforme .

Help please!.

Answer 1

facteurforme is a lambda

Lambda expressions (sometimes called lambda forms) are used to create anonymous functions. The expression lambda parameters: expression yields a function object. The unnamed object behaves like a function object defined with:

def <lambda>(parameters): return expression

As you're supposed to use regionprops and facteurforme uses r.area and r.perimeter which are properties of regionprops it is obvious that you should use a set of region properties as the lambda's argument.

facteureforme calculates the isoperimetric quotient for a given set of region properties.

This quotient is only 1 for a circle (or very close to 1 in a non-theoretical case) and less for anything else. You can use this value to distinguish between circles and rectangles.

Also see Shape Factor: Circularity

r.equivalent_diameter should be renamed r.equivalent_diameterfloat btw.

To get started with your homework I suggest you search the web for regionprops tutorials / examples