draw box with mouse on image in canvas tkinter

1import PIL.Image
2import Image
3import ImageTk
4from Tkinter import *    
5
6
7class ExampleApp(Frame):
8    def __init__(self,master):
9        Frame.__init__(self,master=None)
10        self.x = self.y = 0
11        self.canvas = Canvas(self,  cursor="cross")
12
13        self.sbarv=Scrollbar(self,orient=VERTICAL)
14        self.sbarh=Scrollbar(self,orient=HORIZONTAL)
15        self.sbarv.config(command=self.canvas.yview)
16        self.sbarh.config(command=self.canvas.xview)
17
18        self.canvas.config(yscrollcommand=self.sbarv.set)
19        self.canvas.config(xscrollcommand=self.sbarh.set)
20
21        self.canvas.grid(row=0,column=0,sticky=N+S+E+W)
22        self.sbarv.grid(row=0,column=1,stick=N+S)
23        self.sbarh.grid(row=1,column=0,sticky=E+W)
24
25        self.canvas.bind("<ButtonPress-1>", self.on_button_press)
26        self.canvas.bind("<B1-Motion>", self.on_move_press)
27        self.canvas.bind("<ButtonRelease-1>", self.on_button_release)
28
29        self.rect = None
30
31        self.start_x = None
32        self.start_y = None
33
34        self.im = PIL.Image.open("logo.png")
35        self.wazil,self.lard=self.im.size
36        self.canvas.config(scrollregion=(0,0,self.wazil,self.lard))
37        self.tk_im = ImageTk.PhotoImage(self.im)
38        self.canvas.create_image(0,0,anchor="nw",image=self.tk_im)   
39
40
41    def on_button_press(self, event):
42        # save mouse drag start position
43        self.start_x = self.canvas.canvasx(event.x)
44        self.start_y = self.canvas.canvasy(event.y)
45
46        # create rectangle if not yet exist
47        if not self.rect:
48            self.rect = self.canvas.create_rectangle(self.x, self.y, 1, 1, outline='red')
49
50    def on_move_press(self, event):
51        curX = self.canvas.canvasx(event.x)
52        curY = self.canvas.canvasy(event.y)
53
54        w, h = self.canvas.winfo_width(), self.canvas.winfo_height()
55        if event.x > 0.9*w:
56            self.canvas.xview_scroll(1, 'units') 
57        elif event.x < 0.1*w:
58            self.canvas.xview_scroll(-1, 'units')
59        if event.y > 0.9*h:
60            self.canvas.yview_scroll(1, 'units') 
61        elif event.y < 0.1*h:
62            self.canvas.yview_scroll(-1, 'units')
63
64        # expand rectangle as you drag the mouse
65        self.canvas.coords(self.rect, self.start_x, self.start_y, curX, curY)    
66
67    def on_button_release(self, event):
68        pass    
69
70if __name__ == "__main__":
71    root=Tk()
72    app = ExampleApp(root)
73    app.pack()
74    root.mainloop()
75