Python Pillow - M L with Numpy

In this chapter, we use numpy to store and manipulate image data using python imaging pbrary – “pillow”.

Before proceeding with this chapter open command prompt in administrator mode and execute the following command in it to install numpy −

pip install numpy

Note − This works only if you have PIP installed and updated.

Creating image from Numpy Array

Creating an RGB image using PIL and save it as a jpg file. In the following example we will −

Create a 150 by 250-pixel array.

Fill left half of the array with orange.

Fill right half of the array with blue.

from PIL import Image
import numpy as np

arr = np.zeros([150, 250, 3], dtype=np.uint8)

arr[:,:100] = [255, 128, 0]

arr[:,100:] = [0, 0, 255]

img = Image.fromarray(arr)

img.show()

img.save("RGB_image.jpg")

Output

Creating greyscale images

Creating greyscale images is spghtly different from creating an RGB image. We can use the 2-dimensional array to create a greyscale image.

from PIL import Image
import numpy as np

arr = np.zeros([150,300], dtype=np.uint8)

#Set grey value to black or white depending on x position
   for x in range(300):
      for y in range(150):
         if (x % 16) // 8 == (y % 16)//8:
            arr[y, x] = 0
         else:
            arr[y, x] = 255
img = Image.fromarray(arr)

img.show()

img.save( greyscale.jpg )

Output

Creating numpy array from an Image

You can convert PIL image to numpy array and vice versa. A small program to demonstrate the same is stated below.

Example

#Import required pbraries
from PIL import Image
from numpy import array

#Open Image & create image object
img = Image.open( beach1.jpg )

#Show actual image
img.show()

#Convert an image to numpy array
img2arr = array(img)

#Print the array
print(img2arr)

#Convert numpy array back to image
arr2im = Image.fromarray(img2arr)

#Display image
arr2im.show()

#Save the image generated from an array
arr2im.save("array2Image.jpg")

Output

If you save the above program as Example.py and execute −

It displays the original image.

Displays the array retrieved from it.

Converts the array back into image and displays it.

Since we have used show() method the images are displayed using the default PNG display utipty, as follows.

[[[ 0 101 120]
[ 3 108 127]
[ 1 107 123]
...
...
[[ 38 59 60]
[ 37 58 59]
[ 36 57 58]
...
[ 74 65 60]
[ 59 48 42]
[ 66 53 47]]
[[ 40 61 62]
[ 38 59 60]
[ 37 58 59]
...
[ 75 66 61]
[ 72 61 55]
[ 61 48 42]]
[[ 40 61 62]
[ 34 55 56]
[ 38 59 60]
...
[ 82 73 68]
[ 72 61 55]
[ 63 52 46]]]

Original Image

Image constructed from the array