Where's Wally Problem using Mahotas

In this article we will see how we can find the wally in the given image. Where’s Wally?, also called Where’s Waldo? in North America is a British puzzle books. The books consist of a series of detailed double-page spread illustrations showing dozens or more people doing a variety of amusing things at a given location. Readers are challenged to find a character named Wally hidden in the group.
Image used in the program –

Wally Description : Wally is identified by his red-and-white-striped shirt, bobble hat, and glasses, but many illustrations contain red herrings involving deceptive use of red-and-white striped objects.
In order to do this we will use mahotas library. Mahotas is a computer vision and image processing library for Python. It includes many algorithms implemented in C++ for speed while operating in numpy arrays and with a very clean Python interface.
Command to install mahotas –

pip install mahotas

Below is the implementation –

# importing required libraries 
from pylab import imshow, show 
import mahotas 
import mahotas.demos 
import numpy as np 
  
# loading the image  
wally = mahotas.demos.load('wally') 
  
# showing the original image 
imshow(wally) 
show() 
  
# getting float type value  
# float values are better to use 
wfloat = wally.astype(float) 
  
# spiltting image into red, green and blue channel 
r, g, b = wfloat.transpose((2, 0, 1)) 
  
# white channel 
w = wfloat.mean(2) 
  
# pattern of wally shirt 
# pattern + 1, +1, -1, -1 on vertical axis 
pattern = np.ones((24, 16), float) 
for i in range(2): 
    pattern[i::4] = -1
  
# convolve with the red minus white 
# increase the response where shirt is 
v = mahotas.convolve(r-w, pattern) 
  
# getting maximum value  
mask = (v == v.max()) 
  
# creating mask to tone down the image  
# except the region where wally is 
mask = mahotas.dilate(mask, np.ones((48, 24))) 
  
# subtraction mask from the wally 
np.subtract(wally, .8 * wally * ~mask[:, :, None],  
                   out = wally, casting ='unsafe') 
  
# show the new image 
imshow(wally) 
show() 

Output :

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My Personal Notes

Where’s Wally Problem using Mahotas

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