Python | OpenCV 專案：MediaPipe 手勢控制應用

# detect_hands.py
import cv2
import mediapipe as mp

mp_hands   = mp.solutions.hands
mp_drawing = mp.solutions.drawing_utils

hands = mp_hands.Hands(
    static_image_mode=False,
    max_num_hands=2,
    min_detection_confidence=0.7,
    min_tracking_confidence=0.5,
)

cap = cv2.VideoCapture(0)
print("MediaPipe 手部偵測，按 q 離開")

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

    frame = cv2.flip(frame, 1)   # 水平翻轉，讓畫面如鏡子
    rgb   = cv2.cvtColor(frame, cv2.COLOR_BGR2RGB)
    result = hands.process(rgb)

    if result.multi_hand_landmarks:
        for hand_lm in result.multi_hand_landmarks:
            # 繪製 21 個關鍵點與連線
            mp_drawing.draw_landmarks(
                frame, hand_lm, mp_hands.HAND_CONNECTIONS
            )

    cv2.imshow("Hands", frame)
    if cv2.waitKey(1) & 0xFF == ord("q"):
        break

cap.release()
cv2.destroyAllWindows()

# demo_count_fingers.py
def count_fingers(hand_lm, handedness):
    """
    回傳伸出的手指數量（0~5）
    handedness: "Left" 或 "Right"（MediaPipe 回傳的是鏡像後的手）
    """
    lm = hand_lm.landmark

    # 指尖與第二關節的 ID
    tip_ids  = [4, 8, 12, 16, 20]
    pip_ids  = [3, 6, 10, 14, 18]

    fingers = 0

    # 大拇指：比較 x 軸（左右手方向不同）
    if handedness == "Right":
        if lm[tip_ids[0]].x < lm[pip_ids[0]].x:
            fingers += 1
    else:
        if lm[tip_ids[0]].x > lm[pip_ids[0]].x:
            fingers += 1

    # 其他四指：比較 y 軸（指尖 y < 第二關節 y 表示伸直）
    for i in range(1, 5):
        if lm[tip_ids[i]].y < lm[pip_ids[i]].y:
            fingers += 1

    return fingers

# demo_recognize_gesture.py
def recognize_gesture(hand_lm):
    """辨識特定手勢，回傳手勢名稱"""
    lm = hand_lm.landmark

    tip_ids = [4, 8, 12, 16, 20]
    pip_ids = [3, 6, 10, 14, 18]

    # 各手指是否伸直
    fingers = [lm[tip_ids[i]].y < lm[pip_ids[i]].y for i in range(1, 5)]
    # 大拇指（簡化：只看是否向側邊伸出）
    thumb_open = abs(lm[4].x - lm[3].x) > 0.04

    # 拳頭：所有手指收起
    if not any(fingers) and not thumb_open:
        return "✊ 拳頭"

    # 讚：只有大拇指伸出，其他收起
    if thumb_open and not any(fingers):
        return "👍 讚"

    # 剪刀：食指與中指伸出
    if fingers[0] and fingers[1] and not fingers[2] and not fingers[3]:
        return "✌️ 剪刀"

    # OK：食指與大拇指靠近（其他手指伸出）
    dist = ((lm[4].x - lm[8].x)**2 + (lm[4].y - lm[8].y)**2) ** 0.5
    if dist < 0.06 and fingers[1] and fingers[2] and fingers[3]:
        return "👌 OK"

    # 五指全開
    if all(fingers) and thumb_open:
        return "🖐️ 五指張開"

    return ""

# gesture_painter.py
import cv2
import mediapipe as mp
import numpy as np

mp_hands   = mp.solutions.hands
mp_drawing = mp.solutions.drawing_utils

hands  = mp_hands.Hands(max_num_hands=1,
                         min_detection_confidence=0.7,
                         min_tracking_confidence=0.5)
cap    = cv2.VideoCapture(0)
canvas = None
prev_x, prev_y = None, None
color  = (0, 255, 0)

print("食指繪圖，拳頭清除，按 q 離開")

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

    frame  = cv2.flip(frame, 1)
    h, w   = frame.shape[:2]

    if canvas is None:
        canvas = np.zeros_like(frame)

    rgb    = cv2.cvtColor(frame, cv2.COLOR_BGR2RGB)
    result = hands.process(rgb)

    if result.multi_hand_landmarks:
        hand_lm = result.multi_hand_landmarks[0]
        lm      = hand_lm.landmark

        # 食指指尖位置
        ix = int(lm[8].x * w)
        iy = int(lm[8].y * h)

        # 手指計數判斷手勢
        tip_ids = [8, 12, 16, 20]
        pip_ids = [6, 10, 14, 18]
        finger_count = sum(
            lm[tip_ids[i]].y < lm[pip_ids[i]].y for i in range(4)
        )

        if finger_count == 1:
            # 只伸出食指：繪圖模式
            if prev_x is not None:
                cv2.line(canvas, (prev_x, prev_y), (ix, iy), color, 5)
            prev_x, prev_y = ix, iy
        elif finger_count == 0:
            # 拳頭：清除畫布
            canvas = np.zeros_like(frame)
            prev_x, prev_y = None, None
        else:
            prev_x, prev_y = None, None

        mp_drawing.draw_landmarks(frame, hand_lm, mp_hands.HAND_CONNECTIONS)

    # 疊加畫布
    output = cv2.addWeighted(frame, 0.7, canvas, 0.3, 0)
    cv2.putText(output, "食指:畫  拳頭:清除  q:離開", (10, 30),
                cv2.FONT_HERSHEY_SIMPLEX, 0.7, (255, 255, 0), 2)

    cv2.imshow("Gesture Painter", output)
    if cv2.waitKey(1) & 0xFF == ord("q"):
        break

cap.release()
cv2.destroyAllWindows()