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How to perform basic image processing operations in Python with Pillow?
How to perform basic image processing operations in Python with Pillow?
Aug 02, 2025 am 08:10 AM
Pillow is a powerful and easy-to-use Python image processing library. 1. First install and import the library through pip install pillow; 2. Use Image.open() to open the image, save() to save the image, and the format is automatically recognized by the file extension; 3. resize() can resize the image but not maintain the aspect ratio, thumbnail() creates thumbnails while maintaining the aspect ratio; 4. crop() accepts (left, upper, right, lower) tuples for cropping; 5. rotate() rotates the image counterclockwise at the angle, expand=True can retain the complete image, and transpose() can achieve horizontal or vertical flip; 6. convert('L') to grayscale, convert('1') to 1-bit black and white; 7. Use ImageFilter.BLUR , etc. to apply blur, sharpen, edge detection and other filters; 8. ImageEnhance.Brightness, Contrast, and Color are used to adjust brightness, contrast and saturation respectively; 9. Image information can be obtained through attributes such as size, mode, format; 10. paste() can superimpose one image on another image, supporting transparent channels. Pillow makes image processing simple and efficient, suitable for tasks such as automated thumbnail generation, format conversion and machine learning preprocessing.
Pillow (PIL Fork) is a powerful and easy-to-use library for image processing in Python. It allows you to perform a wide range of basic operations like opening, saving, resizing, cropping, rotating, filtering, and color manipulation. Here's how to handle common image processing tasks using Pillow.
1. Install and Import Pillow
First, install Pillow if you haven't already:
pip install pillow
Then import it in your script:
from PIL import Image, ImageFilter, ImageEnhance
2. Open and Save Images
To load an image from a file:
img = Image.open('input.jpg')
To save it in a different format or location:
img.save('output.png')
Pillow automatically detects the format based on the file extension.
3. Basic Image Operations
Resize an Image
Use resize() to change dimensions. Pass a tuple (width, height):
resized_img = img.resize((800, 600)) resized_img.save('resized.jpg')
?? Note:
resize()doesn't maintain aspect ratio by default. To preserve it, calculate dimensions manually or usethumbnail().
Create a Thumbnail (Preserves Aspect Ratio)
img_copy = img.copy() # Always work on a copy img_copy.thumbnail((800, 600)) # Modifies in place, respects aspect ratio img_copy.save('thumbnail.jpg')
Crop an Image
Specify a bounding box as (left, upper, right, lower):
cropped_img = img.crop((100, 100, 400, 400)) # Crops a 300x300 region cropped_img.save('cropped.jpg')
Rotate an Image
Rotate by a given angle (counterclockwise):
rotated_img = img.rotate(45, expand=True) # expand=True keeps the whole image rotated_img.save('rotated.jpg')
You can also flip or mirror:
flipped_img = img.transpose(Image.FLIP_LEFT_RIGHT) # Horizontal flip # flipped_img = img.transpose(Image.FLIP_TOP_BOTTOM) # Vertical flip flipped_img.save('flipped.jpg')
4. Color and Mode Manipulation
Convert between color modes (eg, RGB, grayscale, black & white):
gray_img = img.convert('L') # Grayscale gray_img.save('grayscale.jpg') bw_img = img.convert('1') # 1-bit black and white (dithered) bw_img.save('black_white.jpg')
5. Apply Filters and Enhancements
Apply Built-in Filters
Use ImageFilter module:
# Blur blurred_img = img.filter(ImageFilter.BLUR) # Sharpen sharpened_img = img.filter(ImageFilter.SHARPEN) # Edge enhancement edges_img = img.filter(ImageFilter.FIND_EDGES) blurred_img.save('blurred.jpg')
Adjust Brightness, Contrast, Saturation
Use ImageEnhance classes:
enhancer = ImageEnhance.Brightness(img) bright_img = enhancer.enhance(1.5) # Increase brightness by 50% bright_img.save('bright.jpg') # Similarly for contrast enhancer = ImageEnhance.Contrast(img) contrast_img = enhancer.enhance(2.0) # Double contrast contrast_img.save('high_contrast.jpg') # For color satisfaction enhancer = ImageEnhance.Color(img) color_img = enhancer.enhance(1.5) # Boost color color_img.save('color_enhanced.jpg')
6. Get Image Information
You can inspect basic image properties:
print("Size:", img.size) # (width, height)
print("Mode:", img.mode) # eg, RGB, L
print("Format:", img.format) # eg, JPEG, PNG
print("Width:", img.width)
print("Height:", img.height)7. Combine Images (Optional)
Paste one image onto another:
base_img = Image.open('background.jpg') overlay = Image.open('logo.png').resize((100, 100)) # Paste overlay at position (50, 50) base_img.paste(overlay, (50, 50), overlay) # Third arg for alpha mask base_img.save('combined.png')
Summary
Pillow makes basic image processing simple and intuitive. Key points:
- Use
Image.open()and.save()for loading and saving. -
.resize(),.crop(),.rotate(),.transpose()for geometry changes. -
.convert()for color mode changes. -
ImageFilterandImageEnhancefor visual effects. - Always work on copies to avoid modifying the original.
With these tools, you can automate common image tasks like thumbnails, format conversion, and preprocessing for machine learning.
Basically just a few lines for most operations — but powerful when chained together.
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