如何使用 tkinter 为形状分配不同的点？

Question

I have tried to search for an answer to my question, but I have not find the solution to my problem, although my question seems to be fairly simple. What I wish to know is how I can, for example, have 2 circles center points on the same location. I am a beginner, so please don't be too harsh.

Answer 1

I don't quite know what information you have when trying to draw these circles, so will assume you know the centre and radius. That's a very good starting point, however, as others have mentioned, tkinter requires the binding box of said circle.

I find everything easier with a diagram, so here is one:

We know the coordinates of the circle's centre (marked "C") and also the radius (indicated by the two lines off "C" - both of length "r"). The first thing I'm going to do is split the coordinates of "C" into different variables which I'll call x _c and y _c (for the x and y values respectively).

Next, I'm going to split A into its x and y values (x _a and y _a ). The edges of the square (our binding box) intersect the circle at the horizontal and vertical (directly left, right, above or below the centre). Taking the horizontal first, we therefore know that x _a is x _c minus the radius. In the same way, we can say that y _a is y _c minus the radius (using tkinter canvas coords - which work from the top-left to bottom-right rather than bottom-left to top-right).

Again, in a similar way, we can say that x _b and y _b (the x and y values of B) are x _c and y _c plus the radius. Combining our coordinate values back together, we get:

A = (xc - r, yc - r)
B = (xc + r, yc + r)

These are the coordinates of the binding box so we can go and pass these straight to tkinter:

#/usr/bin/python3
CENTRE = (100, 100)
RADIUS1 = 20
RADIUS2 = 30
CENTRE_X, CENTRE_Y = CENTRE

import tkinter as tk

root = tk.Tk()

c = tk.Canvas(root, width=200, height=200)
c.pack()
c.create_oval(CENTRE_X - RADIUS1, CENTRE_Y - RADIUS1,
              CENTRE_X + RADIUS1, CENTRE_Y + RADIUS1)
c.create_oval(CENTRE_X - RADIUS2, CENTRE_Y - RADIUS2,
              CENTRE_X + RADIUS2, CENTRE_Y + RADIUS2)

root.mainloop()

The result is two concentric circles in the middle of our canvas.