树莓派opencv python 实例教程二 手势识别 Hand Gesture Recognition

调整屏幕亮度会改变结果。尽量将手完全放在盒子里，避免手臂或手腕进入盒子（因为它会改变面积比）。使用范围值完成，因此可能适用于不同的人的不同颜色范围。

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import cv2
import numpy as np
import math
cap = cv2.VideoCapture(0)

while(1):

    try:  #an error comes if it does not find anything in window as it cannot find contour of max area
          #therefore this try error statement

        ret, frame = cap.read()
        frame=cv2.flip(frame,1)
        kernel = np.ones((3,3),np.uint8)

        #define region of interest
        roi=frame[100:300, 100:300]

        cv2.rectangle(frame,(100,100),(300,300),(0,255,0),0)    
        hsv = cv2.cvtColor(roi, cv2.COLOR_BGR2HSV)

    # define range of skin color in HSV
        lower_skin = np.array([0,20,70], dtype=np.uint8)
        upper_skin = np.array([20,255,255], dtype=np.uint8)

     #extract skin colur imagw  
        mask = cv2.inRange(hsv, lower_skin, upper_skin)

    #extrapolate the hand to fill dark spots within
        mask = cv2.dilate(mask,kernel,iterations = 4)

    #blur the image
        mask = cv2.GaussianBlur(mask,(5,5),100) 

    #find contours
        _,contours,hierarchy= cv2.findContours(mask,cv2.RETR_TREE,cv2.CHAIN_APPROX_SIMPLE)

   #find contour of max area(hand)
        cnt = max(contours, key = lambda x: cv2.contourArea(x))

    #approx the contour a little
        epsilon = 0.0005*cv2.arcLength(cnt,True)
        approx= cv2.approxPolyDP(cnt,epsilon,True)

    #make convex hull around hand
        hull = cv2.convexHull(cnt)

     #define area of hull and area of hand
        areahull = cv2.contourArea(hull)
        areacnt = cv2.contourArea(cnt)

    #find the percentage of area not covered by hand in convex hull
        arearatio=((areahull-areacnt)/areacnt)*100

     #find the defects in convex hull with respect to hand
        hull = cv2.convexHull(approx, returnPoints=False)
        defects = cv2.convexityDefects(approx, hull)

    # l = no. of defects
        l=0

    #code for finding no. of defects due to fingers
        for i in range(defects.shape[0]):
            s,e,f,d = defects[i,0]
            start = tuple(approx[s][0])
            end = tuple(approx[e][0])
            far = tuple(approx[f][0])
            pt= (100,180)

            # find length of all sides of triangle
            a = math.sqrt((end[0] - start[0])**2 + (end[1] - start[1])**2)
            b = math.sqrt((far[0] - start[0])**2 + (far[1] - start[1])**2)
            c = math.sqrt((end[0] - far[0])**2 + (end[1] - far[1])**2)
            s = (a+b+c)/2
            ar = math.sqrt(s*(s-a)*(s-b)*(s-c))

            #distance between point and convex hull
            d=(2*ar)/a

            # apply cosine rule here
            angle = math.acos((b**2 + c**2 - a**2)/(2*b*c)) * 57

            # ignore angles > 90 and ignore points very close to convex hull(they generally come due to noise)
            if angle <= 90 and d>30:
                l += 1
                cv2.circle(roi, far, 3, [255,0,0], -1)

            #draw lines around hand
            cv2.line(roi,start, end, [0,255,0], 2)

        l+=1

        #print corresponding gestures which are in their ranges
        font = cv2.FONT_HERSHEY_SIMPLEX
        if l==1:
            if areacnt<2000:
                cv2.putText(frame,'Put hand in the box',(0,50), font, 2, (0,0,255), 3, cv2.LINE_AA)
            else:
                if arearatio<12:
                    cv2.putText(frame,'0',(0,50), font, 2, (0,0,255), 3, cv2.LINE_AA)
                elif arearatio<17.5:
                    cv2.putText(frame,'Best of luck',(0,50), font, 2, (0,0,255), 3, cv2.LINE_AA)

                else:
                    cv2.putText(frame,'1',(0,50), font, 2, (0,0,255), 3, cv2.LINE_AA)

        elif l==2:
            cv2.putText(frame,'2',(0,50), font, 2, (0,0,255), 3, cv2.LINE_AA)

        elif l==3:

              if arearatio<27:
                    cv2.putText(frame,'3',(0,50), font, 2, (0,0,255), 3, cv2.LINE_AA)
              else:
                    cv2.putText(frame,'ok',(0,50), font, 2, (0,0,255), 3, cv2.LINE_AA)

        elif l==4:
            cv2.putText(frame,'4',(0,50), font, 2, (0,0,255), 3, cv2.LINE_AA)

        elif l==5:
            cv2.putText(frame,'5',(0,50), font, 2, (0,0,255), 3, cv2.LINE_AA)

        elif l==6:
            cv2.putText(frame,'reposition',(0,50), font, 2, (0,0,255), 3, cv2.LINE_AA)

        else :
            cv2.putText(frame,'reposition',(10,50), font, 2, (0,0,255), 3, cv2.LINE_AA)

        #show the windows
        cv2.imshow('mask',mask)
        cv2.imshow('frame',frame)
    except:
        pass

    k = cv2.waitKey(5) & 0xFF
    if k == 27:
        break

cv2.destroyAllWindows()
cap.release()    

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