Mahotas – Getting Mean Value of Image

In this article we will see how we can get the mean value of image in mahotas. Mean value is the sum of pixel values divided by the total number of pixel values. 
Pixel Values Each of the pixels that represents an image stored inside a computer has a pixel value which describes how bright that pixel is, and/or what color it should be. In the simplest case of binary images, the pixel value is a 1-bit number indicating either foreground or background.
Mean is most basic of all statistical measure. Means are often used in geometry and analysis; a wide range of means have been developed for these purposes. In contest of image processing filtering using mean is classified as spatial filtering and used for noise reduction.
In order to do this we will use mean method 

Syntax : img.mean()
Argument : It takes no argument
Return : It returns float32 

Here img is the image loaded using mahotas, which can be done with the help of mahotas.imread(image_name) method.
Note : The image should be filtered before getting mean because it can calculate for one channel at one time
Example 1 :

Python3

# importing required libraries
import numpy as np
import mahotas
from pylab import imshow, show

# loading image
img = mahotas.imread('dog_image.png')

# filtering the image
img = img[:, :, 0]

print("Image with filter")
# showing the image
imshow(img)
show()

# getting mean value
mean = img.mean()

# printing mean value
print("Mean Value for 0 channel : " + str(mean))

Output :

Mean Value for 0 channel : 129.05525723083971

Example 2 :

Python3

# importing required libraries
import mahotas as mh
import mahotas.demos
import numpy as np
from pylab import imshow, show

# getting nuclear image
nuclear = mh.demos.nuclear_image()


# filtering the image
nuclear = nuclear[:, :, 0]

print("Image with filter")
# showing the image
imshow(nuclear)
show()

# getting mean value
mean = nuclear.mean()

# printing mean value
print("Mean Value for 0 channel : " + str(mean))

Output :

Mean Value for 0 channel : 27.490094866071427

Note : For each channel there are different mean value and mean can be a good option to set the threshold value for an image.