from tkinter import *
from tkinter.colorchooser import *


# 创建一个窗口
window = Tk()
# 设置背景颜色
window.configure(background='gray')

# 创建解释说明性文字
instruction = Label(window, text='用鼠标左键在画布上画画', background='gray')
# 把解释说明文字布局到窗口中
instruction.pack()

# 创建颜色选择的标签
colorButton = Button(window, text='选择颜色')
# 把颜色选择标签布局到窗口中
colorButton.pack()

# 创建清空画布的标签
clearButton = Button(window, text='清除')
# 布局到窗口
clearButton.pack()

# 创建画布 宽度500 高度400
my_canvas = Canvas(window, width=500, height=400)
# 把画布布局
my_canvas.pack()

# 改变画笔颜色的程序
my_color = 'black'

# 挑选颜色的函数
def pick_color(event):

    global my_color
    my_color = askcolor()
    my_color = my_color[1]


colorButton.bind('<Button-1>', pick_color)


# 清除画布的方法
def clear(event):
    my_canvas.delete(ALL)


clearButton.bind('<Button-1>', clear)


# 画线程序
def pen_down(event):
    global prevX
    global prevY
    prevX = event.x
    prevY = event.y


my_canvas.bind('<ButtonPress-1>', pen_down)


def draw(event):
    global prevX
    global prevY
    my_canvas.create_line(prevX, prevY, event.x, event.y, fill=my_color)

    prevX = event.x
    prevY = event.y


my_canvas.bind('<B1-Motion>', draw)


# 让窗口循环展示
window.mainloop()