用Tkin中的鼠标事件绘制矩形

Question

这是关于Draw rectangle on mouse click [Python]的。我尝试了第一种解决方案，效果很好。有人能告诉我，如果我想看到正在绘制的矩形，并且一旦鼠标按钮被释放，矩形就固定了，因为我只能在释放按钮后看到绘制的矩形，怎么办。在

任何形式的帮助都将被感激。在

Answer 1

我根据引用的问题修改了代码。现在，当鼠标在画布上拖动时，它将显示矩形。画布显示Lena图像。在

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()

黑色方块画在图像的顶部。希望这有帮助。在