Joining Images using OpenCV

Joining Images using OpenCV

In this article, we will learn how to join images together using OpenCV. We have an image named "Lena" located in the resources folder. Our goal is to stack this image with itself. Initially, we will use the horizontal stack function to achieve this. Here’s a step-by-step guide on how to do it:

1. Load the Image:

   • First, ensure that you have the image named "Lena" in your resources folder.
   • Load the image using OpenCV's cv2.imread() function.

2. Horizontal Stack Function:

   • OpenCV provides an easy way to stack images horizontally using the numpy.hstack() function.
   • The function takes a list of images as an argument and stacks them horizontally.

3. Display the Image:

   • Use OpenCV's cv2.imshow() function to display the stacked image.
   • Make sure to use cv2.waitKey() to keep the image window open until a key is pressed.

4. Complete Script:

   • Below is the complete script to stack images horizontally and display them.

import cv2
import numpy as np

## Introduction
image = cv2.imread('resources/Lena.png')

## Introduction
def stack_images_horizontal(image):
    return np.hstack((image, image))

## Introduction
stacked_image = stack_images_horizontal(image)
cv2.imshow('Stacked Horizontally', stacked_image)
cv2.waitKey(0)
cv2.destroyAllWindows()

5. Handling Different Channels:
   • Sometimes, images might have different channels (e.g., grayscale and RGB).
   • You can create a function that handles stacking images even when they have different channels.

Here's a small function to illustrate this:

def stack_images(image1, image2):
    if image1.shape != image2.shape:
        print("Images have different shapes.")
        return None
    return np.hstack((image1, image2))

## Introduction
image1 = cv2.imread('resources/Lena.png')
image2 = cv2.imread('resources/Example.png')

## Introduction
stacked_image = stack_images(image1, image2)

if stacked_image is not None:
    cv2.imshow('Stacked Images', stacked_image)
    cv2.waitKey(0)
    cv2.destroyAllWindows()

By following this guide, you can easily stack images together using OpenCV. The provided function can also handle images with different channels, ensuring that you can stack them without any issues.

Keywords

• OpenCV
• Image Stacking
• Horizontal Stack
• cv2.imshow()
• np.hstack()
• Handling Image Channels

FAQ

Q1: What is the hstack function used for? A1: The hstack function from the NumPy library is used to stack images horizontally. It takes a list of images and places them side by side.

Q2: How do I display an image using OpenCV? A2: Use the cv2.imshow() function to display an image. You need to provide a window name and the image itself. Use cv2.waitKey(0) to wait for a key press to close the window.

Q3: Can I stack images of different sizes? A3: No, images need to be of the same size to stack them horizontally or vertically. You may need to resize them to the same dimensions before stacking.

Q4: How can I handle images with different channels? A4: You can write a custom function to handle images with different channels, ensuring they are stacked correctly even if one is grayscale and the other is RGB.

Q5: What function is used to load images in OpenCV? A5: The cv2.imread() function is used to load images in OpenCV. You need to provide the path to the image file.