Real-Time Sketching with OpenCV's Webcam Support

Real-Time Sketching with OpenCV's Webcam Support

In an engaging article written by Romilvishol, we delve into the world of computer vision and learn how to draw the movement of objects in real-time using OpenCV in Python.

To achieve this, we need to capture video frames from a camera or video file, preprocess them, detect contours, track object positions, draw contours and movement trails, and display the annotated frame.

Here's a simplified step-by-step guide:

1. Capture video frames from a camera or video file.
2. Preprocess frames by converting them to grayscale and applying thresholding or background subtraction to isolate moving objects.
3. Detect contours of moving objects using .
4. Track object positions over frames by extracting the centroid of each contour.
5. Draw contours and movement trails on the current frame using and .
6. Display the annotated frame using .

Key Steps with OpenCV Functions:

• Use to detect object boundaries in each frame after preprocessing.
• Find each contour’s centroid via image moments:

- Store centroids in a list or deque per object ID to maintain history (movement path). - Use to draw the path (movement trail) linking previous centroids. - Use to outline detected shapes. - Annotate frames with if needed.

Example Simplified Code Skeleton:

```python import cv2 import numpy as np from collections import deque

cap = cv2.VideoCapture(0) # Or path to video file

object_paths = {}

while True: ret, frame = cap.read() if not ret: break

cap.release() cv2.destroyAllWindows() ```

Additional Notes:

• More advanced tracking (to keep consistent object IDs between frames) may require tracking algorithms like SORT, DeepSORT, or using YOLO with tracking libraries, as shown in source [3].
• Using object masks and contour extraction from segmentation models like YOLOv8 segmentation allows more precise outlines of objects, not just bounding boxes [4].
• The key functions are , , , and OpenCV display functions.

This method allows you to visualize object movements in real-time or videos by drawing their contours and connecting their tracked centroids over time to show the motion path on screen [1][2][4].

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