How to save an image created from multiple images?

[Antti Isomursu]

Ok, this is my problem:

I have succesfully created an image by pasting smaller images into
area, created with canvas method:
>>> canvas = Canvas(win, width=canvasX, height=canvasY,
background='white')
""" Then I add images to picture using line below """
>>> canvas.create_image(ax, yy, anchor='nw', image=testi)

So, I got the image i wanted. How can I now save that picture as an
jpeg?