Changing pixel values of an image

We can use the putpixel() function to change a pixel value in an image. Next, let us discuss a popular application of adding noise to an image using the function.

Adding salt and pepper noise to an image

We can add some salt-and-pepper noise to an image by selecting a few pixels from the image randomly and then setting about half of those pixel values to black and the other half to white. The next code snippet shows how to add the noise:

# choose 5000 random locations inside image
im1 = im.copy() # keep the original image, create a copy 
n = 5000
x, y = np.random.randint(0, im.width, n), np.random.randint(0, im.height, n)
for (x,y) in zip(x,y):
 im1.putpixel((x, y), ((0,0,0) if np.random.rand() < 0.5 else (255,255,255))) # salt-and-pepper noise
im1.show()

The following figure shows the output noisy image generated by running the previous code: