Python Pillow - Identifying an Image File

Identifying image files using the Python Pillow (PIL) library involves checking file extensions to determine if a file is likely an image or not. While Pillow itself doesn't have a built-in method to identify image files and we can use functions of os module such as listdir(), path.splitext(), path.is_image_file(), path.join() to filter files based on their extensions as per our user requirements.

Python's os.path module does not provide a direct is_image_file() function for identifying image files. Instead we can typically use the Pillow library (PIL) to check if a file is an image.

However we can create a custom is_image_file() function using os.path in combination with Pillow to check if a file appears to be an image based on its extension.

Here's an example of how we can use os.path to check file extensions and determine if a file is likely an image file −

• We define the is_image_file() function which first checks if the file's extension appears to be a common image format (defined in 'image_extensions'). If the file extension is not recognized, it's assumed not to be an image file.

• For recognized image file extensions the function attempts to open the file as an image using Pillow's Image.open(). If this operation succeeds without errors then the function returns True indicating that the file is a valid image.

• If there is an issue opening the file the function returns False.

• This approach combines os.path for extracting file extensions and Pillow for checking whether the file is a valid image.

Example - Idetifying an Image file

main.py

import os
from PIL import Image

def is_image_file(file_path):
   image_extensions = {".jpg", ".jpeg", ".png", ".gif", ".bmp", ".tiff", ".ico"}  
   #Add more extensions as needed
   _, file_extension = os.path.splitext(file_path)
 
   #Check if the file extension is in the set of image extensions
   return file_extension.lower() in image_extensions

file_path = "Images/butterfly.jpg"
if is_image_file(file_path):
   print("This is an image file.")
   Image.open(file_path)
else:	
   print("This is not an image file.")

Output

This is an image file.

Example - Checking PDF file as Image File

In this example we are passing the file extension as pdf, as it is not a image file extension the result will be not a image file.

main.py

import os
from PIL import Image

def is_image_file(file_path):
   image_extensions = {".jpg", ".jpeg", ".png", ".gif", ".bmp", ".tiff", ".ico"}  
   #Add more extensions as needed
   _, file_extension = os.path.splitext(file_path)
 
   #Check if the file extension is in the set of image extensions
   return file_extension.lower() in image_extensions

file_path = "Images/butterfly.pdf"
if is_image_file(file_path):
   print("This is an image file.")
   Image.open(file_path)
else:	
   print("This is not an image file.")

Output

This is not an image file.