Pinch Distance

Measures the distance between your thumb and index fingertips and shows it as a level from 0 to 100%. This makes a simple volume or brightness control.

Run it

python examples/pinch_distance.py

Code

examples/pinch_distance.py

"""Measure the distance between the thumb and index fingertips.

The bar fills as the fingers open, which makes a simple volume or brightness control.
Press q to quit.
"""

import math

import cv2 as cv

from detectors_world import create_detector

THUMB_TIP = 4
INDEX_TIP = 8
CLOSED, OPEN = 30, 220

cap = cv.VideoCapture(0)
with create_detector("hand", max_hands=1) as hand:
    while cap.isOpened():
        ok, frame = cap.read()
        if not ok:
            break
        frame = cv.flip(frame, 1)
        hands = hand.detect(frame, draw=False)
        if hands:
            thumb, index = hands[0][THUMB_TIP], hands[0][INDEX_TIP]
            distance = math.dist(thumb, index)
            level = min(max((distance - CLOSED) / (OPEN - CLOSED), 0), 1)

            cv.line(frame, thumb, index, (0, 255, 0), 3)
            cv.rectangle(frame, (20, 40), (50, 240), (255, 255, 255), 2)
            cv.rectangle(frame, (20, 240 - int(200 * level)), (50, 240), (0, 255, 0), cv.FILLED)
            cv.putText(frame, f"{level:.0%}", (15, 275), cv.FONT_HERSHEY_SIMPLEX, 0.8, (0, 255, 0), 2)
        cv.imshow("Pinch Distance", frame)
        if cv.waitKey(1) & 0xFF == ord("q"):
            break
cap.release()
cv.destroyAllWindows()

How it works

• hands[0][THUMB_TIP] gives a landmark's (x, y) position directly.
• math.dist() calculates the straight-line distance in pixels.
• level turns that distance into a value from 0 to 1, using CLOSED and OPEN as the range.

Try next

• The distance in pixels changes as your hand moves toward the camera. Divide it by the distance between landmarks 0 and 9 to get a value that doesn't change.
• Adjust CLOSED and OPEN to suit your camera.