[Image-SIG] Re: HOW ? Snapshot Tk canvas as image

[Fredrik Lundh]

Graham Swallow wrote:

> How can I get an image from a Tk canvas.
> (other than rewrite or Ghostscript).
> The following limits are OK (as in screen grab)
>
> image is exact size of VISIBLE PART of canvas
> canvas is update-idle-tasks and not obscured

the following script works on Windows (requires PIL 1.1.4):

    import sys
    import Tkinter
    import ImageGrab

    canvas = Tkinter.Canvas(width=600, height=400)
    canvas.create_line(0, 0, 600, 400, fill="red", width=10)
    canvas.pack()

    canvas.update()

    if sys.platform == "win32":

        # get window location
        x0 = canvas.winfo_rootx()
        y0 = canvas.winfo_rooty()
        x1 = x0 + canvas.winfo_width()
        y1 = y0 + canvas.winfo_height()

        im = ImageGrab.grab((x0, y0, x1, y1))

    else:

        raise NotYetImplemented("oops!")

    im.show()

under X windows, you could probably emulate the grab call by calling
"xwd -id %s" % canvas.winfo_id() and piping the output through xwd-
topnm.  something like this might work:

elif os.name == "posix":

    os.system("xwd -id %s | xwdtopnm >grab.ppm" % canvas.winfo_id())
    im = Image.open("grab.ppm")

    # (for production code, replace grab.ppm with a temporary filename,
    #  and make sure to remove it when done)

</F>