CLI tool to read QR code from MacOS camera image

qr_scanner.py

#!/usr/bin/env uv run --script
# /// script
# dependencies = [
#     "opencv-python",
# ]
# ///

import cv2
import sys

def main():
    # Initialize the OpenCV QR Code detector
    detector = cv2.QRCodeDetector()
    
    # Open connection to the default camera (0 is usually the built-in FaceTime camera)
    cap = cv2.VideoCapture(0)
    
    if not cap.isOpened():
        print("Error: Could not open the macOS camera.", file=sys.stderr)
        print("Please ensure terminal/IDE has Camera permissions in System Settings.", file=sys.stderr)
        return

    print("QR Code Scanner started. Point your camera at a QR code.")
    print("Press 'q' in the video window to quit.")

    previous_data = ""

    while True:
        # Capture frame-by-frame
        ret, frame = cap.read()
        if not ret:
            print("Failed to grab frame.")
            break

        # Detect and decode the QR code from the frame
        data, bbox, _ = detector.detectAndDecode(frame)
        
        # If a QR code is detected and contains data
        if data:
            if data != previous_data:
                print(f"\n[+] Decoded Data: {data}")
                previous_data = data
            
            # Optional: Draw a bounding box around the detected QR code
            if bbox is not None and len(bbox) > 0:
                # bbox returns coordinates as a float array; convert to integers for drawing
                pts = bbox[0].astype(int)
                n = len(pts)
                for i in range(n):
                    cv2.line(frame, tuple(pts[i]), tuple(pts[(i+1) % n]), (0, 255, 0), 3)

        # Display the live camera feed
        cv2.imshow("macOS Camera - QR Scanner", frame)

        # Stop the loop if 'q' key is pressed
        if cv2.waitKey(1) & 0xFF == ord('q'):
            break

    # Clean up and close windows
    cap.release()
    cv2.destroyAllWindows()
    print("\nScanner closed.")

if __name__ == "__main__":
    main()