在Tkinter中使用鼠标事件绘制矩形

Question

这与Draw rectangle on mouse click [Python]有关。我尝试了第一个解决方案，它完美无缺。有人可以告诉我，如果我想看到正在绘制的矩形并且一旦释放鼠标按钮就修复了矩形该怎么办，因为我只能在释放按钮时看到绘制的矩形。

任何形式的帮助都将受到赞赏。

Answer 1

我修改了引用问题的代码。现在，它在画布上拖动鼠标时显示矩形。画布显示Lena图像。

import tkinter as tk # this is in python 3.4. For python 2.x import Tkinter
from PIL import Image, ImageTk



class ExampleApp(tk.Tk):
    def __init__(self):
        tk.Tk.__init__(self)
        self.x = self.y = 0
        self.canvas = tk.Canvas(self, width=512, height=512, cursor="cross")
        self.canvas.pack(side="top", fill="both", expand=True)
        self.canvas.bind("<ButtonPress-1>", self.on_button_press)
        self.canvas.bind("<B1-Motion>", self.on_move_press)
        self.canvas.bind("<ButtonRelease-1>", self.on_button_release)

        self.rect = None

        self.start_x = None
        self.start_y = None


        self._draw_image()


    def _draw_image(self):
         self.im = Image.open('./resource/lena.jpg')
         self.tk_im = ImageTk.PhotoImage(self.im)
         self.canvas.create_image(0,0,anchor="nw",image=self.tk_im)



    def on_button_press(self, event):
        # save mouse drag start position
        self.start_x = event.x
        self.start_y = event.y

        # create rectangle if not yet exist
        #if not self.rect:
        self.rect = self.canvas.create_rectangle(self.x, self.y, 1, 1, fill="black")

    def on_move_press(self, event):
        curX, curY = (event.x, event.y)

        # expand rectangle as you drag the mouse
        self.canvas.coords(self.rect, self.start_x, self.start_y, curX, curY)



    def on_button_release(self, event):
        pass


if __name__ == "__main__":
    app = ExampleApp()
    app.mainloop()

黑色方块绘制在图像的顶部。希望这会有所帮助。