Canvas to Image?

[=?gb2312?q?yu=20huang?= <krocea yahoo com cn>]

Hello,

    I'm using canvas to display a stack of images on
the screen.
    The canvas screen is bigger than my full screen,
so I can't use screenshot to snap it down.

    Question:

    Could I select a patch from the canvas screen and
store it as an image? 

    I mean adding some code to my program in order to
implement it.
    

Best regards,
Yu Huang

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