Tutorial: Working with Images in Python using Pillow

Pillow is a powerful library in Python for image processing, built as a fork of the Python Imaging Library (PIL).

With Pillow, you can perform a variety of operations like loading, editing, and saving images.

In this tutorial, we’ll cover:

1. Installing Pillow

To install Pillow, use pip:

pip install pillow

2. Loading and Displaying Images

The Image module is used to load and display images.

Example: Load and Display an Image

from PIL import Image

# Open an image file
image = Image.open("example.jpg")

# Display the image
image.show()

# Print basic image details
print(f"Format: {image.format}, Size: {image.size}, Mode: {image.mode}")

3. Basic Image Operations

3.1 Resizing an Image

image_resized = image.resize((200, 200))
image_resized.show()

3.2 Cropping an Image

# Define the box (left, upper, right, lower)
box = (50, 50, 200, 200)
cropped_image = image.crop(box)
cropped_image.show()

3.3 Rotating and Flipping an Image

rotated_image = image.rotate(45)  # Rotate 45 degrees
rotated_image.show()

flipped_image = image.transpose(Image.FLIP_LEFT_RIGHT)  # Flip horizontally
flipped_image.show()

4. Image Transformations

4.1 Converting to Grayscale

grayscale_image = image.convert("L")
grayscale_image.show()

4.2 Thumbnail Creation

The thumbnail method preserves the aspect ratio.

thumbnail_image = image.copy()
thumbnail_image.thumbnail((100, 100))
thumbnail_image.show()

5. Adding Text and Drawing Shapes

Use the ImageDraw module for drawing and adding text.

Example: Draw Shapes and Add Text

from PIL import ImageDraw, ImageFont

# Create a drawing object
draw = ImageDraw.Draw(image)

# Draw a rectangle
draw.rectangle((50, 50, 200, 200), outline="red", width=5)

# Draw a circle
draw.ellipse((300, 300, 400, 400), fill="blue", outline="white")

# Add text
font = ImageFont.truetype("arial.ttf", size=24)  # Specify font and size
draw.text((50, 10), "Hello, Pillow!", fill="green", font=font)

image.show()

6. Working with Image Filters

The ImageFilter module provides several built-in filters.

Example: Applying Filters

from PIL import ImageFilter

# Apply a blur filter
blurred_image = image.filter(ImageFilter.BLUR)
blurred_image.show()

# Apply a sharpen filter
sharpened_image = image.filter(ImageFilter.SHARPEN)
sharpened_image.show()

# Apply an edge enhancement filter
edges_image = image.filter(ImageFilter.EDGE_ENHANCE)
edges_image.show()

7. Saving Images

You can save images in different formats using the save method.

Example: Save an Image

# Save as PNG
image.save("output_image.png", "PNG")

# Save with quality (for JPEGs)
image.save("output_image.jpg", "JPEG", quality=90)

Practical Examples

Example 1: Batch Image Resizing

Resize multiple images in a directory to a fixed size.

import os
from PIL import Image

input_folder = "input_images"
output_folder = "output_images"
os.makedirs(output_folder, exist_ok=True)

for filename in os.listdir(input_folder):
    if filename.endswith(".jpg"):
        img = Image.open(os.path.join(input_folder, filename))
        img_resized = img.resize((300, 300))
        img_resized.save(os.path.join(output_folder, filename))
        print(f"Resized and saved: {filename}")

Example 2: Creating an Image Collage

Combine multiple images into a grid.

from PIL import Image

def create_collage(image_files, grid_size, output_file):
    images = [Image.open(img).resize((100, 100)) for img in image_files]

    # Create a blank image for the collage
    collage = Image.new("RGB", (grid_size[0] * 100, grid_size[1] * 100))

    for index, img in enumerate(images):
        x = (index % grid_size[0]) * 100
        y = (index // grid_size[0]) * 100
        collage.paste(img, (x, y))

    collage.save(output_file)
    collage.show()

# Example usage
image_files = ["img1.jpg", "img2.jpg", "img3.jpg", "img4.jpg"]
create_collage(image_files, (2, 2), "collage.jpg")

Example 3: Watermarking an Image

Add a semi-transparent watermark to an image.

from PIL import Image, ImageDraw, ImageFont

def add_watermark(input_image, watermark_text, output_image):
    img = Image.open(input_image).convert("RGBA")
    
    # Create a transparent overlay
    txt = Image.new("RGBA", img.size, (255, 255, 255, 0))
    draw = ImageDraw.Draw(txt)
    font = ImageFont.truetype("arial.ttf", 40)
    
    # Add text in the bottom-right corner
    text_width, text_height = draw.textsize(watermark_text, font=font)
    position = (img.size[0] - text_width - 10, img.size[1] - text_height - 10)
    draw.text(position, watermark_text, fill=(255, 255, 255, 128), font=font)
    
    # Combine the image with the watermark
    watermarked = Image.alpha_composite(img, txt)
    watermarked.save(output_image)
    watermarked.show()

# Example usage
add_watermark("example.jpg", "Watermark Text", "watermarked_image.png")

Conclusion

Pillow is an essential library for image processing in Python. Whether you need to resize images, apply filters, or create collages, Pillow makes it simple and efficient.

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