Question

我试图绘制一个三次贝塞尔曲线但是，我对程序的最后一部分有困难。我似乎无法让tkinter真正画出曲线。它目前只是在tkinter窗口的左上角画一条小线，我不确定我是否以错误的方式做错。

from tkinter import *

root = Tk()

window = Canvas(root, width=800, height=800)
window.pack()

def bezier_curve():
    #create empty list for points
    p = []

    #loops through 4 times to get 4 control points
    for i in range(4):
        while True:
            #user input
            p_input = input("Enter X,Y Coordinates for p" + str(i) + ":")
            #splits the string into x and y coordinates
            p_components = p_input.split(',')
            #checks to see if user hasnt entered two coordinates
            if len(p_components) != 2:
                print("Missing coordinate please try again.")
                p_input = input("Enter starting point X,Y Coordinates:")
            #checks to see if the values can not be converted into floats.
            try:
                x = float(p_components[0])
                y = float(p_components[1])
            except ValueError:
                print("Invalid coordinates", p_components, "please try again.")
            #appends the x and y coordinates as a 2 dimensional array.
            else:
                p.append([float(p_components[0]), float(p_components[1])])
                break
    print(p[0][0])

    #Start x and y coordinates, when t = 0
    x_start = p[0][0]
    y_start = p[0][1]

    #loops through in intervals of 0.1 
    for t in range(0, 11, 1):
        t = i/10
        x=(p[0][0]*(1-t)**3+p[1][0]*3*t*(1-t)**2+p[2][0]*3*t**2*(1-t)+p[3][0]*t**3)
        y=(p[0][1]*(1-t)**3+p[1][1]*3*t*(1-t)**2+p[2][1]*3*t**2*(1-t)+p[3][1]*t**3)

        draw_line = window.create_line(x,y,x_start,y_start)
        #updates initial values
        x_start = x
        y_start = y


bezier_curve()
root.mainloop()

Answer 1

是;画线中的一个小错误：

#loops through in intervals of 0.1 
for t in range(0, 11, 1):
    t = i/10

您已将t指定为循环变量，它应为i。

for t in range(0, 11, 1):
    ^
    This shoud be i

Answer 2

@figbeam回答是正确的，并修复了你的问题我发现你的输入机制很繁琐，所以我改变了它以允许在画布上点击以捕获贝塞尔曲线的控制点。

import tkinter as tk


def draw_bezier():
    # Start x and y coordinates, when t = 0
    x_start = control_points[0][0]
    y_start = control_points[0][1]

    p = control_points

    # loops through
    n = 50
    for i in range(50):
        t = i / n
        x = (p[0][0] * (1-t)**3 + p[1][0] * 3 * t * (1-t)**2 + p[2][0] * 3 * t**2 * (1-t) + p[3][0] * t**3)
        y = (p[0][1] * (1-t)**3 + p[1][1] * 3 * t * (1-t)**2 + p[2][1] * 3 * t**2 * (1-t) + p[3][1] * t**3)

        canvas.create_line(x, y, x_start, y_start)
        # updates initial values
        x_start = x
        y_start = y


def get_point(event):
    global control_points
    point = x, y = (event.x, event.y)
    control_points.append(point)
    canvas.create_oval(x, y, x+3, y+3)
    if len(control_points) == 4:
        draw_bezier()
        control_points = []


if __name__ == '__main__':

    control_points = []

    root = tk.Tk()

    canvas = tk.Canvas(root, width=800, height=800)
    canvas.pack()

    canvas.bind('<Button-1>', get_point)

    root.mainloop()

麻烦绘制Bezier曲线

2 个答案: