python - 在 Tkinter 中使用鼠标事件绘制矩形

Question

这是关于 Draw rectangle on mouse click [Python] 的.我尝试了第一个解决方案并且效果很好。有人可以告诉我，如果我想看到正在绘制的矩形并且在释放鼠标按钮后矩形得到固定怎么办，因为我只能在释放按钮后看到绘制的矩形。

我们将不胜感激任何形式的帮助。

Answer 1

我修改了引用问题的代码。现在它在 Canvas 上拖动鼠标时显示矩形。 Canvas 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 block 绘制在图像上方。希望这会有所帮助。