cv2_mouse_input_example.py

import cv2
import numpy as np

######################################################################

def mouse_input(window):
  
    '''Return an x, y location from a click in a window using cv2.'''

    # mouse callback to collect input
    def _on_mouse(event, x, y, flag, param):
        if event == cv2.EVENT_LBUTTONDOWN:
            print 'got click at ({}, {})'.format(x, y)
            param[0] = x
            param[1] = y

    # no-op mouse callback to stop collecting input
    def _null_mouse(event, x, y, flag, param):
        pass

    # list object to hold coords
    mouse_coords = [-1, -1]
         
    # install the callback in the window
    cv2.setMouseCallback(window, _on_mouse, mouse_coords)

    # collect coords
    print 'click anywhere in the {} window'.format(window)

    # go until valid coords or ESC hit
    while mouse_coords[0] < 0:
        k = cv2.waitKey(5)
        if k == 27: # ESC
            print 'canceled!'
            break

    # stop collecting coords
    cv2.setMouseCallback(window, _null_mouse)

    # return result
    return tuple(mouse_coords)

######################################################################

image = cv2.imread('purpleflower.png')
win = 'Display'

cv2.namedWindow(win)
cv2.imshow(win, image)

x, y = mouse_input(win)