create a rectangle around all the points returned from mediapipe hand landmark detection just like cv2.boundingrect does

Question

I am using following code to detect hand landmarks using mediapipe

import cv2
import mediapipe as mp

mphands = mp.solutions.hands
hands = mphands.Hands()
mp_drawing = mp.solutions.drawing_utils
cap = cv2.VideoCapture(0)

while True:
    _, frame = cap.read()
    framergb = cv2.cvtColor(frame, cv2.COLOR_BGR2RGB)
    result = hands.process(framergb)
    hand_landmarks = result.multi_hand_landmarks
    if hand_landmarks:
        for handLMs in hand_landmarks:
            mp_drawing.draw_landmarks(frame, handLMs, mphands.HAND_CONNECTIONS)
            print("\n\n\n")
    cv2.imshow("Frame", frame)

    cv2.waitKey(1)

I just want a rectangle around all the points returned by the detector Please tell if there is any way to do so built in mediapipe or using opencv

Answer 1

1. Before the while loop, determine the width and height each frame will be:

_, frame = cap.read()

h, w, c = frame.shape

2. For each landLM detected, define the initial variables for smallest x and y coordinates, and the largest x and y coordinates. The first two variables will later act as the starting point of the rectangle, and the last two variables will later act as the last point of the rectangle:

            x_max = 0
            y_max = 0
            x_min = w
            y_min = h

3. Loop through the handLM variable, and finding the x and y coordinates of each point of the hand:

            for lm in handLMs.landmark:
                x, y = int(lm.x * w), int(lm.y * h)

4. Update the minimum and maximum x and y variables as new coordinates are being detected:

                if x > x_max:
                    x_max = x
                if x < x_min:
                    x_min = x
                if y > y_max:
                    y_max = y
                if y < y_min:
                    y_min = y

5. Finally, draw the rectangle with the points:

            cv2.rectangle(frame, (x_min, y_min), (x_max, y_max), (0, 255, 0), 2)

Altogether:

import cv2
import mediapipe as mp

mphands = mp.solutions.hands
hands = mphands.Hands()
mp_drawing = mp.solutions.drawing_utils
cap = cv2.VideoCapture(0)

_, frame = cap.read()

h, w, c = frame.shape

while True:
    _, frame = cap.read()
    framergb = cv2.cvtColor(frame, cv2.COLOR_BGR2RGB)
    result = hands.process(framergb)
    hand_landmarks = result.multi_hand_landmarks
    if hand_landmarks:
        for handLMs in hand_landmarks:
            x_max = 0
            y_max = 0
            x_min = w
            y_min = h
            for lm in handLMs.landmark:
                x, y = int(lm.x * w), int(lm.y * h)
                if x > x_max:
                    x_max = x
                if x < x_min:
                    x_min = x
                if y > y_max:
                    y_max = y
                if y < y_min:
                    y_min = y
            cv2.rectangle(frame, (x_min, y_min), (x_max, y_max), (0, 255, 0), 2)
            mp_drawing.draw_landmarks(frame, handLMs, mphands.HAND_CONNECTIONS)
    cv2.imshow("Frame", frame)

    cv2.waitKey(1)