Скачать или смотреть How to Draw a Rectangle over an Image and Get the Coordinates in Python

Learn how to use Python to draw a rectangle on an image and retrieve its coordinates using mouse event listeners. Simple guide for beginners!
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Drawing a Rectangle on an Image in Python

In the realm of image processing in Python, one common task is the ability to interactively select areas of an image. This article will guide you through the process of creating a program that allows you to draw a rectangle over an image and retrieves the coordinates, height, and width of the rectangle you've drawn.

The Challenge

You want a program that:

Opens an image.

Allows you to click and drag to form a rectangle.

Captures and displays the starting coordinates, height, and width of the rectangle.

Using libraries like argparse and cv2 can make this task manageable, but if you're unsure how to begin, follow this breakdown!

Breaking Down the Solution

The solution to this problem involves the following key components:

Image Displayer

Mouse Event Listener

We'll initially focus on the mouse event listener to capture the rectangle's coordinates.

Step 1: Setting Up the Mouse Listener

For tracking mouse events, you will need a library that allows for event listening. We recommend using pynput, a user-friendly library that is well-documented. Here’s how to get started with it:

Getting Started with pynput

Install pynput: You can install pynput using pip if you haven't done so:

[[See Video to Reveal this Text or Code Snippet]]

Understanding Mouse Events: Familiarize yourself with the documentation, focusing specifically on the on_click event.

Implementing the Code: Write the following code snippet to create a mouse listener. It captures the initial and final coordinates of the rectangle when you click and drag.

[[See Video to Reveal this Text or Code Snippet]]

Step 2: Running the Program

Run the program.

Click and drag anywhere on your screen. Release the mouse button when you're done.

The coordinates and the size of the rectangle will be printed in the console.

Step 3: Improving Your Program

Once your mouse event listener is working, you can integrate it with an image display functionality using cv2. Here are some advanced tips:

Displaying the Image: Use cv2.imshow to display the image while enabling rectangle drawing.

Scaling Factor: If the image size is large, implement a scaling factor to adjust the coordinates accordingly.

Conclusion

This simple yet effective approach allows you to interactively select areas in an image and retrieve necessary dimensions easily. As you progress, feel free to refine your program and ask questions or seek assistance as needed. Remember, coding is all about experimenting and learning!



By following this guide, you'll have a base program that not only allows rectangle drawing over images but also lays the groundwork for more complex image processing tasks. Happy coding!