simple_interacting_window_in_cv2.py

# https://opencv-python-tutroals.readthedocs.io/en/latest/py_tutorials/py_gui/py_trackbar/py_trackbar.html#trackbar

import cv2
import numpy as np

class GUIHandler(object):

    def onChangeSend(self,x):

        self.A = cv2.getTrackbarPos('A', self.window_name)
        self.B = cv2.getTrackbarPos('B', self.window_name)

        self.update_text()

        print("Data=", [self.A, self.B])

    def update_text(self):
        self.text = ""+str(self.A)+" "+str(self.B)

    def __init__(self):
        self.text = ""

    def start_window_rendering(self):

        # Create a black image, a window
        h = 75
        img = np.zeros((h, 512, 3), np.uint8)
        font = cv2.FONT_HERSHEY_SIMPLEX
        position = (0, h - 25)
        fontScale = 0.8
        fontColor = (128, 128, 128)
        lineType = 2

        self.window_name = 'InteractiveWindow'
        cv2.namedWindow(self.window_name)

        # create trackbars for color change
        cv2.createTrackbar('A', self.window_name, 0, 1000, self.onChangeSend)
        cv2.createTrackbar('B', self.window_name, 0, 100, self.onChangeSend)

        self.onChangeSend(x=None) # toggle once at start

        while (1):
            # also keep another inf. loop

            cv2.imshow(self.window_name, img)
            k = cv2.waitKey(1) & 0xFF
            if k == 27:
                break

            # get current positions of four trackbars
            r = cv2.getTrackbarPos('A', self.window_name)
            r = int(r)

            img[:] = [r, r, r]
            #text = 'Select value: (0 to 1000 => %)'
            text = self.text
            cv2.putText(img, text, position, font, fontScale, fontColor, lineType)

        cv2.destroyAllWindows()


from threading import Thread

gui = GUIHandler()
thread = Thread(target=gui.start_window_rendering())
thread.start()