I want a python program with a dialgo window that captures an image from the webcam. I also want that in that dialgo window there is a colour selector that uses the selected colour to apply a mask for the selected colour. I want all this with opencv

import cv2
import numpy as np

def nothing(x):
    pass

# Create a black image, a window
img = np.zeros((300,512,3), np.uint8)
cv2.namedWindow('image')

# create trackbars for color change
cv2.createTrackbar('R','image',0,255,nothing)
cv2.createTrackbar('G','image',0,255,nothing)
cv2.createTrackbar('B','image',0,255,nothing)

cap = cv2.VideoCapture(0)

while(True):
    # get current positions of four trackbars
    r = cv2.getTrackbarPos('R','image')
    g = cv2.getTrackbarPos('G','image')
    b = cv2.getTrackbarPos('B','image')

    # Read the frame
    ret, frame = cap.read()
    if ret:
        # Flip the image
        frame = cv2.flip(frame,1)
        # Convert BGR