我想用 tkinter 在 python中可視化一個演算法（格雷厄姆掃描）。我想為演算法設定影片，但我被卡住了。
我基本上想繪制和洗掉線條，但我對canvas.after()的理解不足以使其作業。
draw_line()回傳線物件，但是當我在canvas.after(..., draw_line, ...)中呼叫它時，我看不到獲取回傳值的方法或如何呼叫另一個canvas.after()來如果由于延遲而尚未呼叫函式draw_line()，則更改顏色/洗掉該行。
提前致謝。
from tkinter import *
import math
import random
class Point:
def __init__(self, _x, _y, _a=0):
self.x = _x
self.y = _y
self.angle = _a
def get_co(self):
return self.x, self.y
def draw_hull(hull):
for i in range(len(hull) - 1):
canvas.create_line(hull[i][0], hull[i][1], hull[i 1][0], hull[i 1][1], fill="red", width=2)
def draw_line(p1, p2, color="yellow"):
return canvas.create_line(p1.x, p1.y, p2.x, p2.y, fill=color, width=2)
def convex_hull(list_points):
# find bottom point
bottom_point = Point(math.inf, math.inf)
for point in list_points:
if point[1] < bottom_point.y:
bottom_point = Point(point[0], point[1])
# calculate angles between the bottom point and the other points
points = []
for point in list_points:
if point != bottom_point.get_co():
new_point = Point(point[0], point[1])
angle = calculate_angle(bottom_point, new_point)
new_point.angle = angle
points.append(new_point)
# sort the points by angle
swaps = None
while swaps != 0:
swaps = 0
for i in range(len(points) - 1):
point1 = points[i]
point2 = points[i 1]
if point1.angle > point2.angle:
points[i], points[i 1] = points[i 1], points[i]
swaps = 1
# go through the points and add them to the convex hull
# if the angle between 3 points ever exeeds 180 degrees, discard the middle point
hull = [bottom_point, points[0]]
i = 1
while i < len(points):
####### DRAW LINE #######
canvas.after(i*500, draw_line, hull[-2], hull[-1])
##############
# check angle
angle = calculate_angle(hull[-2], hull[-1], points[i])
if angle == -1:
########## DELETE LINE ##########
# change color of line to red and delete it a bit later
# canvas.itemconfig(line, fill="red")
# canvas.after(i*500 250, canvas.delete, line)
####################
# pop the point of the stack
hull.pop()
else:
########## CHANGE COLOR OF LINE ##########
# change color of line to green
# canvas.itemconfig(line, fill="green")
####################
# move to the next point
hull.append(points[i])
i = 1
# add bottom point again for loop
hull.append(bottom_point)
# give easy return list (with coordinate-tupels not class objects)
output = []
for point in hull:
output.append(point.get_co())
return output
def calculate_angle(point1, point2, point3=None):
if point3 is None:
if point2.x - point1.x == 0:
return 90
elif point2.x - point1.x > 0:
return math.degrees(math.atan((point2.y - point1.y)/(point2.x - point1.x)))
else:
return 180 - math.degrees(math.atan((point2.y - point1.y)/(point1.x - point2.x)))
else:
v1 = Point(point1.x - point2.x, point1.y - point2.y)
v2 = Point(point3.x - point2.x, point3.y - point2.y)
det = (v1.x * v2.y) - (v2.x * v1.y)
if det < 0:
return 1
else:
return -1
window = Tk()
window.geometry("1000x600")
canvas = Canvas(window, width=1000, height=600)
canvas.pack()
POINTSIZE = 2
points = []
for i in range(100):
x = random.randint(50, 950)
y = random.randint(50, 550)
points.append((x, y))
canvas.create_oval(x - POINTSIZE, y - POINTSIZE, x POINTSIZE, y POINTSIZE, fill="black")
hull = convex_hull(points)
# draw_hull(hull)
window.mainloop()
uj5u.com熱心網友回復：
如果您對代碼有任何疑問，請告訴我。因為我不知道從哪里開始解釋，因為我對您的代碼進行了重大更改。
無論如何，如果你在CodeReview上再次分享你的代碼，我會很高興，請告訴我。因為使用起來很有趣，而且你的代碼對我來說似乎不完整。
快樂編碼：
import tkinter as tk
import random
import math
class Point:
def __init__(self, _x, _y, _a=0):
self.x = _x
self.y = _y
self.angle = _a
return None
def get_co(self):
return self.x, self.y
class Window(tk.Tk):
def __init__(self,_w,_h):
super().__init__()
self.POINTSIZE = 2
self.points = []
self.swaps = None
self.count = 1
self.delay = 200
self.title('Graham scan simulation')
self.toolbar = tk.Frame(self,background='grey')
self.refresh_button = tk.Button(self.toolbar,text='Refresh',
command=self.refresh)
self.start_button = tk.Button(self.toolbar,text='Start',
command = self.convex_hull)
self.canvas = tk.Canvas(self,width=_w,height=_h)
self.toolbar.pack(side=tk.TOP,fill=tk.BOTH,expand=True)
self.refresh_button.pack(side=tk.LEFT)
self.start_button.pack(side=tk.LEFT)
self.canvas.pack(side=tk.BOTTOM,fill=tk.BOTH,expand=True)
def generate_points(self):
for point_instance in self.points:
yield point_instance
def find_bottom_point(self):
bottom_point = Point(math.inf,math.inf)
for point in self.generate_points():
if point.y < bottom_point.y:
bottom_point = point
return bottom_point
def calculate_angle(self,point1, point2):
if point2.x - point1.x == 0:
return 90
elif point2.x - point1.x > 0:
return math.degrees(math.atan((point2.y - point1.y)/(point2.x - point1.x)))
else:
return 180 - math.degrees(math.atan((point2.y - point1.y)/(point1.x - point2.x)))
def calculate_angels_by_bottom_point(self,bottom_point):
for point in self.generate_points():
if point != bottom_point:
angle = self.calculate_angle(bottom_point,point)
point.angle = angle
def sort_points(self,event_variable):
if self.swaps != 0:
self.swaps = 0
for i in range(len(self.points)-1):
point1 = self.points[i]
point2 = self.points[i 1]
if point1.angle > point2.angle:
self.points[i], self.points[i 1] = self.points[i 1], self.points[i]
self.swaps = 1
if self.swaps == 0:
event_variable.set(1)
self.after(20,self.sort_points,event_variable)
def check_angle(self,point1,point2,point3):
v1 = Point(point1.x - point2.x, point1.y - point2.y)
v2 = Point(point3.x - point2.x, point3.y - point2.y)
det = (v1.x * v2.y) - (v2.x * v1.y)
if det < 0:
return 1
else:
return -1
def draw_line(self,p1,p2,color='yellow'):
return self.canvas.create_line(p1.x,p1.y, p2.x,p2.y, fill='yellow',tags='line')
def clear_red_lines(self,p1,p2):
shapes = self.canvas.find_withtag('line')
for shape in shapes:
if self.canvas.itemcget(shape,'fill') == 'red':
coords = self.canvas.coords(shape)
overlapped = self.canvas.find_overlapping(*coords)
for i in overlapped:
coords2 = self.canvas.coords(i)
if coords == coords2:
self.canvas.delete(i)
self.canvas.delete(shape)
def animated_draw(self,hull):
if self.count != len(self.points):
line = self.draw_line(hull[-2],hull[-1])
check_mark = self.check_angle(hull[-2],hull[-1],self.points[self.count])
if check_mark == -1:
self.canvas.itemconfig(line,fill='red')
self.after(self.delay-100,lambda:self.clear_red_lines(hull[-2],hull[-1]))
hull.pop()
else:
self.canvas.itemconfig(line,fill='green')
hull.append(self.points[self.count])
self.count = 1
self.after(self.delay,self.animated_draw,hull)
def convex_hull(self):
bottom_point = self.find_bottom_point()
self.calculate_angels_by_bottom_point(bottom_point)
event_variable = tk.IntVar(self,value=0)
self.sort_points(event_variable)
self.wait_variable(event_variable)
self.points.pop(0)
self.animated_draw(hull = [bottom_point, self.points[0]])
def generate_listpoints(self,_amount):
'''using a generator for memory purpose'''
for i in range(_amount):
x = random.randint(50, 950)
y = random.randint(50, 550)
yield x,y
def refresh(self):
self.swaps = None
self.count = 1
self.points= []
self.populate_canvas()
def populate_canvas(self):
self.canvas.delete('all')
for x,y in self.generate_listpoints(100):
self.points.append(Point(x, y))#instead of creating throwing instances away.
self.canvas.create_oval(x - self.POINTSIZE,
y - self.POINTSIZE,
x self.POINTSIZE,
y self.POINTSIZE,
fill="black")
root = Window(1000,600)
root.mainloop()
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