clickCropTut.py

# 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)

# load the image, clone it, and setup the mouse callback function
filename = raw_input("Enter filename: ")
image = cv2.imread(filename)
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("q"):
		break

y1 = refPt[0][1]
y2 = refPt[1][1]
x1 = refPt[0][0]
x2 = refPt[1][0]
xRange = x2 - x1
yRange = y2 - y1

# 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)
	print "x1 ", x1
	print "y1 ", y1
	print "x2 ", x2
	print "y2 ", y2
	print "xRange", xRange
	print "yRange", yRange
	cv2.waitKey(0)

# close all open windows
cv2.destroyAllWindows()