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Mahotas – Image Stretching

  • Last Updated : 10 Jul, 2020

In this article we will see how we can do image stretching in mahotas. Contrast stretching (often called normalization) is a simple image enhancement technique that attempts to improve the contrast in an image by `stretching’ the range of intensity values it contains to span a desired range of values, e.g. the the full range of pixel values that the image type concerned allows.

In this tutorial we will use “lena” image, below is the command to load it.

mahotas.demos.load('lena')

Below is the lena image

In order to do this we will use mahotas.stretch method

Syntax : mahotas.stretch(img)



Argument : It takes image object as argument

Return : It returns image object

Note : Input image should be filtered or should be loaded as grey

In order to filter the image we will take the image object which is numpy.ndarray and filter it with the help of indexing, below is the command to do this

image = image[:, :, 0]

Below is the implementation




# importing required libraries
import mahotas
import mahotas.demos
from pylab import gray, imshow, show
import numpy as np
import matplotlib.pyplot as plt
    
# loading iamge
img = mahotas.demos.load('lena')
    
# filtering image
img = img.max(2)
  
print("Image")
    
# showing image
imshow(img)
show()
  
# strecting image
new_img = mahotas.stretch(img)
   
  
# Stretched image
print("Stretched Image")
imshow(new_img)
show()

Output :

Image

Stretched Image

Another example




# importing required libraries
import mahotas
import numpy as np
from pylab import gray, imshow, show
import os
import matplotlib.pyplot as plt
   
# loading iamge
img = mahotas.imread('dog_image.png')
  
  
# fltering image
img = img[:, :, 0]
    
print("Image")
    
# showing image
imshow(img)
show()
  
# strecting image
new_img = mahotas.stretch(img)
   
  
# Stretched image
print("Stretched Image")
imshow(new_img)
show()

Output :

Image

Stretched Image

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