How to export two mouse coordinates [(x0,y0),(x1,y1)] to a txt file in python, with opencv

Question

I'm currently working on a program of object detection. my initial work is to read mouse coordinates and export them to a text file (for the further process).

I tried some code from another link ( https://www.pyimagesearch.com/2015/03/09/capturing-mouse-click-events-with-python-and-opencv/ ). It did work, but I don't know how to add these kinds of file-exporting functions to the original code. Any help will be much appreciated!

when I run a command in terminal like "python click_and_crop.py --image img_0001_c0.pgm ", I expected to get a txt file with content like "355, 53, 424, 107”, so that in the future I could call this function to get more mouse coordinates from more pictures. however, i got “[[(299, 190), (421, 285)]]” (without "").

# USAGE
# python click_and_crop.py --image img_0001_c0.pgm

# 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
str1 = []
path_name = 'mouseCoordinates.txt'

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)
        print(refPt[0][0], refPt[0][1], refPt[1][0], refPt[1][1])
        str1.append(refPt)
        cv2.imshow("image", image)
        mouseXY = open(path_name, 'w')
        mouseXY.write(str(str1))
        mouseXY.close()


# 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()

# USAGE
# python click_and_crop.py --image img_0001_c0.pgm

# 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
str1 = []
path_name = 'mouseCoordinates.txt'

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)
        print(refPt[0][0], refPt[0][1], refPt[1][0], refPt[1][1])
        str1.append(refPt[0])
        cv2.imshow("image", image)
        mouseXY = open(path_name, 'w')
        mouseXY.write()
        mouseXY.close()


# 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()

Answer 1

You could write a function something like this to take the mouse pointers as input and append to a file.

def write_to_file(x, y, a, b):
    '''
    Writes the mouse coordinates to a text file
    '''
    # open the mouse coordinates
    with open('mouseCoordinates.txt', 'a') as f:
        # create a string ready to write to the file
        coordinates = str(x) + ',' + str(y) + ',' + str(a) + ',' + str(b) + '\n'

        # write to file
        f.write(coordinates)

Then you'd input the coordinates something like this?

write_to_file(refPt[0][0], refPt[0][1], refPt[1][0], refPt[1][1])