I have an image saved as `image.png`. The workflow of my task is this:

1. Load image in Tkinter along with a "select two points" button below the image
2. The user left-clicks with the mouse twice on two points of the image
3. **When he selects the first point, that specific point gets highlighted (say in red, or whichever color); then he selects the second point and also this second point gets highlighted**
4. The (x,y) coordinates of the two points are stored in global variables and will be later used
5. Once the user has selected two points, a second "Done!" button appears. When this button is clicked the GUI closes. N.B I would like the two points to remain highlighted until the user clicks the closing button so that he has an idea of where he/she clicked

I managed to solve all steps, except **step 3**. The most similar thing that I found is to create a rectangle with `canvas.create_rectangle(x,y,x+1,y+1,fill="red")`, but first I would prefer a circle and second I don't manage to link the `canvas` to my `Label`

Any help would be appreciated :D

here is my code so far:

```
root = Tk()  # create a window

frame = Frame(root)  # define upper frame
middleframe = Frame(root)  # define middle frame
exitFrame = Frame(root)  # define exit frame
frame.pack()  # pack the frame
middleframe.pack()  # pack the subframe
exitFrame.pack(side = 'bottom')  # pack the exit frame

# function that closes the GUI
def close_window(): 
    root.destroy()

# load the image
img = PhotoImage(file="image.png")  # save the image
panel = Label(frame, image=img)  # display the image as a label
panel.grid(row=0, column=0)  # pack the image

# make the user select some points
global x_Coordinates  # initialize empty list for storing x-axis coordinates
global y_Coordinates  # initialize empty list for storing y-axis coordinates
x_Coordinates = []
y_Coordinates = []

clicks = 0
def countClicks():
  global clicks # this will use the variable to count
  clicks = clicks + 1  # increment "clicks"
  if clicks == 2: # if the user has selected 2 points, add a button that closes the window
      exit_button = Button(exitFrame, state = "normal", text = "Done!", command = close_window)  # link the closing function to the button
      exit_button.grid(row=2, column=0, pady=5)  # set button position with "grid"        
pass

def selectPoints():  # function called when user clicks the button "select two points"
    panel.bind("<Button 1>", saveCoordinates)  #  link the function to the left-mouse-click event
    exit_button = Button (exitFrame, state = "disabled", text = "Done!", command = close_window)  # link closing function to the button
    exit_button.grid(row=2, column=0, pady=5)  # set button position with "grid"
    button_select_points.config(state = "disabled") # switch button state to "disabled"

def saveCoordinates(event): # function called when left-mouse-button is clicked   
    x_coordinate = event.x  # save x and y coordinates selected by the user
    y_coordinate = event.y
    x_Coordinates.append(x_coordinate)  # append to external list
    y_Coordinates.append(y_coordinate)  # append to external list
    countClicks()  # invoke function "countClicks"

button_select_points = Button(middleframe, text = "select two points", command = selectPoints)  # insert button and link it to "selectPoints"
button_select_points.grid(row=1, column=0, pady=5)  # set button position with "grid"

root.mainloop()  # keep the GUI open

```