from math import sqrt
from tkinter import *

def click(click_event):
    global prev
    try:
        canvas.create_line(prev.x, prev.y, click_event.x, click_event.y, width=2, fill='green')
        S.append(click_event)
    except:
        prev = click_event
        S.append(click_event)
        return
    prev = click_event
def distance(a, b):
    return sqrt((a[0] - b[0]) ** 2 + (a[1] - b[1]) ** 2)
def point_line_distance(point, start, end):
    if (start == end):
        return distance(point, start)
    else:
        n = abs(
            (end[0] - start[0]) * (start[1] - point[1]) -
            (start[0] - point[0]) * (end[1] - start[1])
        )
        d = sqrt(
            (end[0] - start[0]) ** 2 + (end[1] - start[1]) ** 2
        )
        return n / d
def rdp(points, epsilon):
    # """Reduces a series of points to a simplified version that loses detail, but
    # maintains the general shape of the series.
    #  Сводит ряд точек к упрощенной версии, которая теряет детализацию, но
    # сохраняет общую форму серии.
    # """
    dmax = 0.0
    index = 0
    for i in range(1, len(points) - 1):
        d = point_line_distance(points[i], points[0], points[-1])
        if d > dmax:
            index = i
            dmax = d
    if dmax>= epsilon:
        results = rdp(points[:index + 1], epsilon)[:-1] + rdp(points[index:], epsilon)
    else:
        results = [points[0], points[-1]]
    return results
def move(move_event):
    global prev
    canvas.create_line(prev.x, prev.y, move_event.x, move_event.y, width=2,  fill='green')
  #  canvas.create_line( rdp(points[:index + 1], epsilon=0.5), width=2)
    rdp(prev[prev.x], 0,5)[:-1] + rdp(prev[prev.y], 0,5)
    prev = move_event  # what does this do ?
def action():
    print(S)
master = Tk()
canvas = Canvas(master, width=600, height=300)
canvas.pack(padx=20, pady=20)
canvas.bind('<Button-1>', click)
but1=Button(master,text='show',command=action);but1.pack()
S=[]
#canvas.bind('<B1-Motion>', move)

mainloop()