OpenCV camera mire : a simple script to help telescope collimation (secondary alignment)

mirecam.py

#!/usr/bin/env python3

import cv2

"""
OpenCV camera mire: a simple script to help telescope collimation (secondary
alignment)

Require OpenCV, binary build are included in this package:
 - pip install opencv-python

Press 'q' to exit.
"""

refPt = ()
radius_old = radius_current = 65

cap = cv2.VideoCapture(0)
# Force Camera resolution
# cap.set(cv2.CAP_PROP_FRAME_WIDTH, 1600)
# cap.set(cv2.CAP_PROP_FRAME_HEIGHT, 1200)
# print(cap.get(cv2.CAP_PROP_FRAME_WIDTH), cap.get(cv2.CAP_PROP_FRAME_HEIGHT))

# frame center
cap_center = (int(cap.get(cv2.CAP_PROP_FRAME_WIDTH) * 0.5),
              int(cap.get(cv2.CAP_PROP_FRAME_HEIGHT) * 0.5))


def distance(x, y, a, b):
    # Manhattan : abs(x-a) + abs(y-b)
    # Tchebychev : max(abs(x-a), abs(y-b))
    # return abs(x-a) + abs(y-b)
    xa = x - a
    yb = y - b
    # TODO: optimize/simplify here
    if abs(xa) > abs(yb):
        if x > cap_center[0]:
            value = xa * -1
        else:
            value = xa
    else:
        if y > cap_center[1]:
            value = yb * -1
        else:
            value = yb
    return value


def update_circle(event, x, y, flags, param):
    global refPt, radius_current, radius_old
    if event == cv2.EVENT_LBUTTONDOWN:
        refPt = (x, y)
    elif event == cv2.EVENT_LBUTTONUP:
        refPt = ()
        radius_old = radius_current
    if refPt:
        cursor_distance = distance(*refPt, x, y)
        radius_current = min(cap_center[1] - 20,
                             max(20, radius_old + cursor_distance))


# create window
w_name = 'MireCam'
cv2.namedWindow(w_name, cv2.WINDOW_GUI_NORMAL | cv2.WINDOW_AUTOSIZE)
cv2.setMouseCallback(w_name, update_circle)

# Draw until exit
while (cv2.waitKey(1) & 0xFF != ord('q')):
    # Capture frame-by-frame
    ret, frame = cap.read()

    # Our operations on the frame come here
    img = cv2.cvtColor(frame, cv2.COLOR_RGB2RGBA)
    img = cv2.circle(img, cap_center, radius_current, (0, 0, 255), 1,
                     cv2.LINE_AA)

    # Display the resulting frame
    cv2.imshow(w_name, img)

# When everything done, release the capture
cap.release()
cv2.destroyAllWindows()