How to Flip Image in Python: Simple Methods Explained

You can flip an image in Python using the Pillow library with Image.transpose() or using cv2.flip() from OpenCV. These methods let you flip images horizontally, vertically, or both by specifying the flip mode.

Syntax

Here are the basic ways to flip images using two popular Python libraries:

• Pillow: Use Image.transpose(method) where method can be Image.FLIP_LEFT_RIGHT for horizontal flip or Image.FLIP_TOP_BOTTOM for vertical flip.
• OpenCV: Use cv2.flip(src, flipCode) where flipCode is 1 for horizontal, 0 for vertical, and -1 for both flips.

python

from PIL import Image
import cv2

# Pillow syntax
image = Image.open('image.jpg')
flipped_image = image.transpose(Image.FLIP_LEFT_RIGHT)

# OpenCV syntax
image_cv = cv2.imread('image.jpg')
flipped_cv = cv2.flip(image_cv, 1)

Example

This example shows how to flip an image horizontally using Pillow and OpenCV, then save the flipped images.

python

from PIL import Image
import cv2

# Flip image horizontally using Pillow
image = Image.open('example.jpg')
flipped_image = image.transpose(Image.FLIP_LEFT_RIGHT)
flipped_image.save('flipped_pillow.jpg')

# Flip image horizontally using OpenCV
image_cv = cv2.imread('example.jpg')
flipped_cv = cv2.flip(image_cv, 1)
cv2.imwrite('flipped_opencv.jpg', flipped_cv)

print('Images flipped and saved successfully.')

Output

Images flipped and saved successfully.

Common Pitfalls

Common mistakes when flipping images include:

• Using the wrong flip mode number in OpenCV, which can flip the image in an unintended direction.
• Forgetting to save or display the flipped image after processing.
• Not handling file paths correctly, causing file not found errors.

Always check the flip mode and confirm the output visually.

python

import cv2

# Wrong flip code (vertical instead of horizontal)
image = cv2.imread('example.jpg')
flipped_wrong = cv2.flip(image, 0)  # flips vertically
cv2.imwrite('flipped_wrong.jpg', flipped_wrong)

# Correct flip code
flipped_correct = cv2.flip(image, 1)  # flips horizontally
cv2.imwrite('flipped_correct.jpg', flipped_correct)

Quick Reference

Library	Function	Flip Mode	Description
Pillow	Image.transpose(method)	Image.FLIP_LEFT_RIGHT	Flip image horizontally
Pillow	Image.transpose(method)	Image.FLIP_TOP_BOTTOM	Flip image vertically
OpenCV	cv2.flip(src, flipCode)	1	Flip image horizontally
OpenCV	cv2.flip(src, flipCode)	0	Flip image vertically
OpenCV	cv2.flip(src, flipCode)	-1	Flip image both horizontally and vertically

Key Takeaways

Use Pillow's Image.transpose() with FLIP_LEFT_RIGHT or FLIP_TOP_BOTTOM to flip images easily.

OpenCV's cv2.flip() uses flipCode 1 for horizontal and 0 for vertical flips.

Always verify the flip direction to avoid unexpected results.

Remember to save or display the flipped image after processing.

Handle file paths carefully to prevent errors when loading images.