python opencv 鼠標提取矩形（Rectangle）ROI

• 方法：獲取鼠標點擊事件

• 代碼

  # import the necessary packages
  import argparse
  import cv2
  # initialize the list of reference points and boolean indicating
  # whether cropping is being performed or not
  refPt = []
  cropping = False
  def click_and_crop(event, x, y, flags, param):
  	# grab references to the global variables
  	global refPt, cropping
  	# if the left mouse button was clicked, record the starting
  	# (x, y) coordinates and indicate that cropping is being
  	# performed
  	if event == cv2.EVENT_LBUTTONDOWN:
  		refPt = [(x, y)]
  		cropping = True
  	# check to see if the left mouse button was released
  	elif event == cv2.EVENT_LBUTTONUP:
  		# record the ending (x, y) coordinates and indicate that
  		# the cropping operation is finished
  		refPt.append((x, y))
  		cropping = False
  		# draw a rectangle around the region of interest
  		cv2.rectangle(image, refPt[0], refPt[1], (0, 255, 0), 2)
  		cv2.imshow("image", image)
  
  
  # construct the argument parser and parse the arguments
  ap = argparse.ArgumentParser()
  ap.add_argument("-i", "--image", required=True, help="Path to the image")
  args = vars(ap.parse_args())
  # load the image, clone it, and setup the mouse callback function
  image = cv2.imread(args["image"])
  clone = image.copy()
  cv2.namedWindow("image")
  cv2.setMouseCallback("image", click_and_crop)
  # keep looping until the 'q' key is pressed
  while True:
  	# display the image and wait for a keypress
  	cv2.imshow("image", image)
  	key = cv2.waitKey(1) & 0xFF
  	# if the 'r' key is pressed, reset the cropping region
  	if key == ord("r"):
  		image = clone.copy()
  	# if the 'c' key is pressed, break from the loop
  	elif key == ord("c"):
  		break
  # if there are two reference points, then crop the region of interest
  # from teh image and display it
  if len(refPt) == 2:
  	roi = clone[refPt[0][1]:refPt[1][1], refPt[0][0]:refPt[1][0]]
  	cv2.imshow("ROI", roi)
  	cv2.waitKey(0)
  # close all open windows
  cv2.destroyAllWindows()
  

• 結果
  

參考資料

https://github.com/xuyangcao/random_walker_gui
Capturing mouse click events with Python and OpenCV