Read Image using Python Imaging Library

Python Imaging Library(PIL) is an open source package for image processing that performs read, write and simple mathematical and logical manipulations on the image. In this post, let’s demonstrate the uses of PIL library in performing various operations on images. For plotting the image alone, matplotlib will be used.

Python script:

from PIL import Image,ImageChops

import matplotlib.pyplot as plt

img = Image.open("poppies.jpg");

plt.imshow(img);

plt.show();

#Grayscale Image

Gimg = img.convert('L');

plt.imshow(Gimg,cmap='gray');

plt.show();

#Display Red channel, Green channel and Blue Channel

r,g,b = img.split()

c1 = ImageChops.constant(r,0);

Red = Image.merge("RGB",(r,c1,c1));

plt.imshow(Red);

plt.show();

Green = Image.merge("RGB",(c1,g,c1));

plt.imshow(Green);

plt.show();

Blue = Image.merge("RGB",(c1,c1,b));

plt.imshow(Blue);

plt.show();

EXPLANATION:

img = Image.open("poppies.jpg");

The Image module from PIL is used to read the image ‘poppies.jpg’ into the variable ‘img’ as RGB image.

Gimg = img.convert('L');

The above syntax converts the RGB image into grayscale.

plt.imshow(Gimg,cmap='gray');

The command mentioned displays the monochromatic image with the colormap ‘gray’.

r,g,b = img.split();

This splits the RGB image ‘img’ and stores the Red component in ‘r’, green component in ‘g’and blue component in ‘b’

Let’s keep the Red channel undisturbed and replace other channels with zeros.

c1 = ImageChops.constant(r,0);

Create an image of same size of ‘img’ filled with zeros.

The above syntax will replace all the values in the image ‘r’ with the constant value ‘0’

Red = Image.merge("RGB",(r,c1,c1));

plt.imshow(Red);

plt.show();

Merge the three components to create RGB image. For red component, image ‘r’ is used and for green and blue component, the zero filled image ‘c1’ is used.

Similarly, the other channels are displayed as RGB components.

Yellow = Image.merge("RGB",(r,g,c1));

plt.imshow(Yellow);

plt.show();

Red and Green channels are used while the blue channel is filled with zeros.

The Variable explorer shows the list of variables used in the python script. The type of the variable is Image and it contains 640 rows by 353 columns.

The Mode ‘RGB’ indicates that the image is color image with Red, Green and Blue components. The Mode ‘L’ indicates that the image is grayscale or monochrome.

Let’s explore the pixel values of the image ‘img’. In the Variable explorer window, right click on the corresponding variable and click Edit. The pixel values with respect to the position will be displayed in a table format.