Matplotlib - Image Thumbnail

Thumbnails, smaller and compressed versions of original images, serve as essential components in various applications, including image previews, web development, and optimizing the loading speed of web pages and applications with heavy images.

In this tutorial, we'll explore using Matplotlib to efficiently generate image thumbnails. Matplotlib takes the support of the Python Pillow library for image processing and allows us to easily generate thumbnails from existing images.

Image thumbnail in Matplotlib

Matplotlib offers the thumbnail() function within its image module to generate thumbnails with customizable parameters, allowing users to efficiently create scaled-down versions of images for various purposes.

Following is the syntax of the function −

Syntax

matplotlib.image.thumbnail(infile, thumbfile, scale=0.1, interpolation='bilinear', preview=False)

Here are the details of its parameters −

  • infile − The input image file. As you know that Matplotlib relies on Pillow for image reading, so it supports a wide range of file formats, including PNG, JPG, TIFF, and others.

  • thumbfile − The filename or file-like object where the thumbnail will be saved.

  • scale − The scale factor for the thumbnail. It determines the size reduction of the thumbnail relative to the original image. A smaller scale factor generates a smaller thumbnail.

  • interpolation − The interpolation scheme used in the resampling process. This parameter specifies the method used to estimate pixel values in the thumbnail.

  • preview − If set to True, the default backend (presumably a user interface backend) will be used, which may raise a figure if show() is called. If set to False, the figure is created using FigureCanvasBase, and the drawing backend is selected as Figure.savefig would normally do.

The function returns a Figure instance containing the thumbnail. This Figure object can be further manipulated or saved as needed.

Generating Thumbnails for a single image

Matplotlib supports various image formats like png, pdf, ps, eps svg, and more, making it flexible for different use cases.

Example

Here is an example that creates a thumbnail for a single .jpg image.

import matplotlib.pyplot as plt
import matplotlib.image as mpimg

input_image_path = "Images/Tajmahal.jpg"
output_thumbnail_path = "Images/Tajmahal_thumbnail.jpg"

# Load the original image
img = mpimg.imread(input_image_path)

# Create a thumbnail using Matplotlib
thumb = mpimg.thumbnail(input_image_path, output_thumbnail_path, scale=0.15)

print(f"Thumbnail generated for {input_image_path}. Saved to {output_thumbnail_path}")

Output

If you visit the folder where the images are saved you can observe both the original and output Thumbnail images as shown below −

image_thumbnail_ex1

Generating Thumbnails for multiple Images

Consider a scenario where you have multiple images in a directory, and you want to generate thumbnails for each of them.

Example

Here is an example that creates thumbnails of multiple PNG images in a directory. Save the following script as generate_thumbnails.py file.

from argparse import ArgumentParser
from pathlib import Path
import sys
import matplotlib.image as image

parser = ArgumentParser(description="Generate thumbnails of PNG images in a directory.")
parser.add_argument("imagedir", type=Path)
args = parser.parse_args()

if not args.imagedir.is_dir():
   sys.exit(f"Could not find the input directory {args.imagedir}")

outdir = Path("thumbs")
outdir.mkdir(parents=True, exist_ok=True)
for path in args.imagedir.glob("*.png"):
   outpath = outdir / path.name
   try:
      fig = image.thumbnail(path, outpath, scale=0.15)
      print(f"Saved thumbnail of {path} to {outpath}")
   except Exception as e:
      print(f"Error generating thumbnail for {path}: {e}")

Then run the script as follows in command prompt 

python generate_thumbnails.py /path/to/all_images

Output

On executing the above program, will create a directory named "thumbs" and generate thumbnails for PNG images in your working directory. If it encounters an image with a different format, it will print an error message and continue processing other images.

Saved thumbnail of Images\3d_Star.png to thumbs\3d_Star.png
Saved thumbnail of Images\balloons_noisy.png to thumbs\balloons_noisy.png
Saved thumbnail of Images\binary image.png to thumbs\binary image.png
Saved thumbnail of Images\black and white.png to thumbs\black and white.png
Saved thumbnail of Images\Black1.png to thumbs\Black1.png
Saved thumbnail of Images\Blank.png to thumbs\Blank.png
Saved thumbnail of Images\Blank_img.png to thumbs\Blank_img.png
Saved thumbnail of Images\Circle1.png to thumbs\Circle1.png
Saved thumbnail of Images\ColorDots.png to thumbs\ColorDots.png
Saved thumbnail of Images\colorful-shapes.png to thumbs\colorful-shapes.png
Saved thumbnail of Images\dark_img1.png to thumbs\dark_img1.png
Saved thumbnail of Images\dark_img2.png to thumbs\dark_img2.png
Saved thumbnail of Images\decore.png to thumbs\decore.png
Saved thumbnail of Images\deform.png to thumbs\deform.png
Saved thumbnail of Images\Different shapes.png to thumbs\Different shapes.png
Error generating thumbnail for Images\Different shapes_1.png: not a PNG file
Saved thumbnail of Images\Ellipses.png to thumbs\Ellipses.png
Error generating thumbnail for Images\Ellipses_and_circles.png: not a PNG file
Saved thumbnail of Images\images (1).png to thumbs\images (1).png
Saved thumbnail of Images\images (3).png to thumbs\images (3).png
Saved thumbnail of Images\images.png to thumbs\images.png
Saved thumbnail of Images\image___1.png to thumbs\image___1.png
Saved thumbnail of Images\Lenna.png to thumbs\Lenna.png
Saved thumbnail of Images\logo-footer-b.png to thumbs\logo-footer-b.png
Saved thumbnail of Images\logo-w.png to thumbs\logo-w.png
Saved thumbnail of Images\logo.png to thumbs\logo.png
Saved thumbnail of Images\logo_Black.png to thumbs\logo_Black.png
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