The next code block shows how slicing and masking with numpy arrays can be used to create a circular mask on the lena image:
lena = mpimg.imread("../images/lena.jpg") # read the image from disk as a numpy ndarrayprint(lena[0, 40])# [180 76 83]# print(lena[10:13, 20:23,0:1]) # slicinglx, ly, _ = lena.shapeX, Y = np.ogrid[0:lx, 0:ly]mask = (X - lx / 2) ** 2 + (Y - ly / 2) ** 2 > lx * ly / 4lena[mask,:] = 0 # masksplt.figure(figsize=(10,10))plt.imshow(lena), plt.axis('off'), plt.show()
The following figure shows the output of the code:
