python 中的 function 内的 IF 循环

Question

I have a function that I would like to perform an if statement inside of. I know this is not possible in Python so I have added a while loop before I implement the if statement but it seems like the while loop is not stopping, or perhaps it maybe another issue.

def hough(frame): 
    
    #calculate the median 
    medianFrame = np.median(randframes,axis=0).astype(dtype=np.uint8)
    grayMedianFrame = cv2.cvtColor(medianFrame, cv2.COLOR_BGR2GRAY)
    
    gframe = cv2.cvtColor(frame,cv2.COLOR_BGR2GRAY) #grayscale frame
    dframe = cv2.absdiff(gframe, grayMedianFrame)  #remove background

    blurred = cv2.GaussianBlur(dframe,(11,11),cv2.BORDER_DEFAULT)  #Gausian blur with standard deviation of 11
    
    while True: 
        
        circles = cv2.HoughCircles(blurred, cv2.HOUGH_GRADIENT,1,120,param1= 50, param2=30,minRadius=0,maxRadius=0)
        
        if circles is None: 
            radius.append(0)
            continue
        
        else: 
            circles = np.uint16(np.around(circles))
            
            for j in circles[0, :]: 
            
                # draw the outer circle
                cv2.circle(frame, (j[0], j[1]), j[2], (0, 0, 255), 2)
                # draw the center of the circle
                cv2.circle(frame, (j[0], j[1]), 2, (0, 255, 0), 9)
                
                radius.append(circles[0][0][2])
     
       break 

    return frame

The varaibles not defined inside the function have been done so but for the purpose of simplicity I have not included them.

EDIT : I have made some changes thanks to the comments, however the issue still exists

EDIT 2 : The code works fine but it seems to be an issue when cirlces return None .

Answer 1

I can not comment so writing it here, Your requirement is not so much clear, first of all if is not a loop, secondly there is nothing we can understand when to break the While loop, i am simplifying your issue, here is sample Code.

if circles is None: 
     radius.append(0)
     continue
else:
     break

The continue in this situation is also not necessary since after the if no more code to run inside the while

Answer 2

Before replying, let me point that if command refers to a statement, and not a loop (more infos here )

According to here :

The continue statement is used to skip the rest of the code inside a loop for the current iteration only.

In your specific case, when the condition of the if statement is True, you append the value 0 to the radius list and then you continue with the next iteration of the while loop. Since the loop is while True: it continues infinitely. If what you wanted to achieve was to exit from the loop when the condition on the if statement is achieved, then one way may be to use the break operator instead the continue one.

Answer 3

I am assume at the Moment that you just want a working Hough Transform function. There is a good example from OpenCV itself. Providing solutions for Java , C++ and python :

Hough Transform

Answer 4

def hough(frame): 
    
    #calculate the median 
    medianFrame = np.median(randframes,axis=0).astype(dtype=np.uint8)
    grayMedianFrame = cv2.cvtColor(medianFrame, cv2.COLOR_BGR2GRAY)
    
    gframe = cv2.cvtColor(frame,cv2.COLOR_BGR2GRAY) #grayscale frame
    dframe = cv2.absdiff(gframe, grayMedianFrame)  #remove background

    blurred = cv2.GaussianBlur(dframe,(11,11),cv2.BORDER_DEFAULT)  #Gausian blur with standard deviation of 11

    circles = cv2.HoughCircles(blurred, cv2.HOUGH_GRADIENT,1,120,param1= 50, param2=30,minRadius=0,maxRadius=0)
        
    if circles is None: 
        return [0]
    else: 
        circles = np.uint16(np.around(circles))
        output = []  
        for j in circles[0, :]: 
            
            # draw the outer circle
            cv2.circle(frame, (j[0], j[1]), j[2], (0, 0, 255), 2)
            # draw the center of the circle
            cv2.circle(frame, (j[0], j[1]), 2, (0, 255, 0), 9)
                
           output.append(circles[0][0][2])
    return output


## main program
radius = []
for frame in frames:
    radius.append(hough(frame))