14.6 Reading and writing images

The module PIL.Image comes with some functions for handling images. The following will read a JPEG image, print the shape and type, and then create a resized image, and write the new image to a file:

import PIL.Image as pil   # imports the Pillow module

# read image to array
im=pil.open("test.jpg")
print(im.size)   # (275, 183)  
                 # Number of pixels in horizontal and vertical directions
# resize image
im_big = im.resize((550, 366))
im_big_gray = im_big.convert("L") # Convert to grayscale

im_array=array(im)

print(im_array.shape)
print(im_array.dtype)   # unint 8
# write result to new image file
im_big_gray.save("newimage.jpg")

PIL creates an image object that can easily be converted to a NumPy array. As an array object, images are stored with pixel values in the range 0...255 as 8-bit unsigned integers (unint8). The third shape value shows how many color channels the image...