Python Tkinter使用PIL将画布保存为图像

正如在this post中所提到的,我尝试使用PIL在画布和内存中并行绘制,以便我可以将其保存为jpeg而不是postscript.它似乎工作,直到我发现我用PIL保存的一些图像与画布上绘制的图像不一样.

我假设来自PIL图像绘制模块功能的canvas.create_line和draw.line类似,并且应该给出类似的输出.

以下是出了什么问题：

例如,当我绘制“T”时,它似乎没问题(左边是我的绘图,右边是保存的图像).

但是当我绘制“A”时,输出图像看起来有点奇怪.

这是我目前的代码：

import Tkinter as tk
import Image,ImageDraw

class ImageGenerator:
    def __init__(self,parent,posx,posy,*kwargs):
        self.parent = parent
        self.posx = posx
        self.posy = posy
        self.sizex = 200
        self.sizey = 200
        self.b1 = "up"
        self.xold = None
        self.yold = None 
        self.coords= []
        self.drawing_area=tk.Canvas(self.parent,width=self.sizex,height=self.sizey)
        self.drawing_area.place(x=self.posx,y=self.posy)
        self.drawing_area.bind("<Motion>",self.motion)
        self.drawing_area.bind("<ButtonPress-1>",self.b1down)
        self.drawing_area.bind("<ButtonRelease-1>",self.b1up)
        self.button=tk.Button(self.parent,text="Done!",width=10,bg='white',command=self.save)
        self.button.place(x=self.sizex/7,y=self.sizey+20)
        self.button1=tk.Button(self.parent,text="Clear!",command=self.clear)
        self.button1.place(x=(self.sizex/7)+80,y=self.sizey+20)

        self.image=Image.new("RGB",(200,200),(255,255,255))
        self.draw=ImageDraw.Draw(self.image)

    def save(self):
        print self.coords
        self.draw.line(self.coords,(0,128,0),width=3)
        filename = "temp.jpg"
        self.image.save(filename)

    def clear(self):
        self.drawing_area.delete("all")
        self.coords=[]

    def b1down(self,event):
        self.b1 = "down"

    def b1up(self,event):
        self.b1 = "up"
        self.xold = None
        self.yold = None

    def motion(self,event):
        if self.b1 == "down":
            if self.xold is not None and self.yold is not None:
                event.widget.create_line(self.xold,self.yold,event.x,event.y,smooth='true',width=3,fill='blue')
                self.coords.append((self.xold,self.yold))

        self.xold = event.x
        self.yold = event.y

if __name__ == "__main__":
    root=tk.Tk()
    root.wm_geometry("%dx%d+%d+%d" % (400,400,10,10))
    root.config(bg='white')
    ImageGenerator(root,10)
    root.mainloop()

我哪里出错了,我应该怎么做才能保存画布上绘制的完全相同的图片作为jpeg图像？