Desktop QR Scanner removes a surprisingly common interruption: grabbing a phone just to decode a QR code already visible on your computer. The app takes a full-screen screenshot, runs OpenCV's QR detector over it, then draws a transparent overlay around each detected code with the decoded value and a copy action.
How it works
The scanner uses mss for fast screen capture, converts the screenshot into an OpenCV frame, and calls detectAndDecodeMulti so multiple QR codes can be found in one pass. The Tkinter UI then opens a topmost transparent overlay, draws rounded bounding boxes over the detected coordinates, and places decoded text near each code.
I also handled high-DPI display scaling explicitly. The screenshot is captured in physical pixels, while Tkinter positions windows in logical screen coordinates, so the overlay rescales the detected points before drawing. That detail is what makes the result line up correctly on Retina-style displays.
Why I built it
This is a compact utility project, but it touches several practical desktop concerns: global-ish shortcuts, screen capture, image decoding, transparent overlays, clipboard integration, and platform coordinate systems. The result is small, but the workflow is immediate: press the shortcut, read the screen, copy the value, continue working.