Function circle

Synopse

This function creates a binary circle image.

g = circle(s, r, c)
- g:output: circle image.
- s:input: Image. [rows cols], output image dimensions.
- r:input: Double. radius.
- c:input: Image. [row0 col0], center of the circle.



In [18]:

    
import numpy as np
def circle(s, r, c):
    
    rows, cols = s[0], s[1]
    rr0,  cc0  = c[0], c[1]
    rr, cc = np.meshgrid(range(rows), range(cols), indexing='ij')
    g = (rr - rr0)**2 + (cc - cc0)**2 <= r**2
    return g

Description

Creates a binary image with dimensions given by s, radius given by r and center given by c. The pixels inside the circle are one and outside zero.

Equation

$$ g(x,y) = (x-x_c)^2 + (y-y_c)^2 \leq r^2 $$

Examples



In [1]:

    
testing = (__name__ == "__main__")
if testing:
    ! jupyter nbconvert --to python circle.ipynb
    import numpy as np
    import sys,os
    ia898path = os.path.abspath('../../')
    if ia898path not in sys.path:
        sys.path.append(ia898path)
    import ia898.src as ia









    



[NbConvertApp] Converting notebook circle.ipynb to python
[NbConvertApp] Writing 1364 bytes to circle.py

Showing a numerical example



In [2]:

    
if testing:
    F = ia.circle([5,7], 2, [2,3])
    print (F.astype(np.uint8))









    



[[0 0 0 1 0 0 0]
 [0 0 1 1 1 0 0]
 [0 1 1 1 1 1 0]
 [0 0 1 1 1 0 0]
 [0 0 0 1 0 0 0]]

Printing the generated image



In [4]:

    
if testing:
    import matplotlib.pyplot as plt
    import matplotlib.image as mpimg
    %matplotlib inline
    f = ia.circle([200,300], 90, [100,150])
    ia.adshow(f,'circle')

Contributions

Luis Antonio Prado, 1st semester 2017