Question

So I’ve been trying to figure out how to find the distance between two objects on a canvas and I’ve exhausted most relevant links on Google with little success.

I’m trying to make it so that it calculates the distance between the drawn ovals and the line on the canvas.

from __future__ import division
from Tkinter import *
import tkMessageBox

class MyApp(object):
    def __init__(self):
        self.root = Tk()
        self.root.wm_title("Escape")
        self.canvas = Canvas(self.root, width=800, height=800, bg='white')
        self.canvas.pack()
        self.canvas.create_line(100, 100, 200, 200, fill='black')
        self.canvas.bind("<B1-Motion>", self.tracer)
        self.root.mainloop()

    def tracer(self, e):
        self.canvas.create_oval(e.x-5, e.y-5, e.x+5, e.y+5, fill='blue', outline='blue')
        rx = "%d" % (e.x)
        ry = "%d" % (e.y)
        print rx, ry
MyApp()

Answer 1

Two circles:

dist = math.sqrt((circle1.x-circle2.x)**2 + (circle1.y-circle2.y)**2) - circle1.r - circle2.r

Kind of obvious, their Euclid distance is calculated using the Pythagorean theorem.

Point/segment:

 a = segment[1].y - segment[0].y
 b = segment[0].x - segment[1].x
 c = - segment[0].x * a - segment[0].y * b 
 dx = segment[1].x - segment[0].x
 dy = segment[1].y - segment[0].y
 nc0 = - segment[0].x * dx - segment[0].y * dy
 nc1 = - segment[1].x * dx - segment[1].y * dy
 if ((dx * x + dy * y + nc0) < 0) dist = math.sqrt((x-segment[0].x)**2 + (y-segment[0].y)**2)
 elif((dx * x + dy * y + nc1) < 0) dist = math.sqrt((x-segment[1].x)**2 + (y-segment[1].y)**2)
 else dist = (a*x + b*y + c) / math.sqrt(a**2 + b**2)

Circle/segment – same as point/segment, just substract circle’s radius

Polygon/polygon – Loop through each vertex of polygon 1 and segment of polygon 2, then loop through each vertex of polygon 2 and segment of polygon 1, then find the smallest.

Don’t use magic numbers inside your code. That radius of 5 isn’t good.