How to Create Thumbnail in Python Using Pillow

You can create a thumbnail in Python using the Pillow library by opening an image and calling its thumbnail() method with the desired size. This method resizes the image while keeping its aspect ratio, making it easy to generate smaller preview images.

Syntax

To create a thumbnail, you first open an image with Image.open(), then call thumbnail(size) on it. The size is a tuple like (width, height) that sets the maximum size of the thumbnail. The image is resized in place, keeping its aspect ratio.

python

from PIL import Image

image = Image.open('path/to/image.jpg')
image.thumbnail((128, 128))  # Resize image to max 128x128
image.save('path/to/thumbnail.jpg')

Example

This example opens an image file, creates a thumbnail with a maximum size of 100x100 pixels, and saves the thumbnail as a new file. It shows how easy it is to generate a smaller version of an image for previews.

python

from PIL import Image

# Open an existing image
image = Image.open('example.jpg')

# Create a thumbnail with max size 100x100
image.thumbnail((100, 100))

# Save the thumbnail
image.save('example_thumbnail.jpg')

print('Thumbnail created successfully.')

Output

Thumbnail created successfully.

Common Pitfalls

• Not installing Pillow: You must install Pillow with pip install Pillow before using it.
• Using resize() instead of thumbnail(): resize() changes the image size but does not keep the aspect ratio automatically.
• Calling thumbnail() multiple times on the same image can cause unexpected results because it modifies the image in place.
• Not saving the thumbnail after creating it will not store the smaller image.

python

from PIL import Image

image = Image.open('example.jpg')

# Wrong: resize without aspect ratio
resized = image.resize((100, 100))  # May distort image
resized.save('wrong_thumbnail.jpg')

# Right: use thumbnail to keep aspect ratio
image = Image.open('example.jpg')
image.thumbnail((100, 100))
image.save('correct_thumbnail.jpg')

Quick Reference

Here is a quick summary of the main steps and tips for creating thumbnails in Python:

Step	Description
Install Pillow	Run pip install Pillow to add the library.
Open Image	Use Image.open('file.jpg') to load your image.
Create Thumbnail	Call image.thumbnail((width, height)) to resize.
Save Thumbnail	Use image.save('thumbnail.jpg') to save the result.
Keep Aspect Ratio	thumbnail() keeps the image proportions automatically.

Key Takeaways

Use Pillow's thumbnail() method to create thumbnails that keep aspect ratio.

Always save the image after creating the thumbnail to store the smaller version.

Install Pillow with pip install Pillow before running your code.

Avoid using resize() if you want to keep the image proportions.

The thumbnail() method modifies the image in place, so reopen if needed.