Rectangle detection

[Peter Reid]

I'm trying to detect and extract a rectangular area of an image.  The image is a graph with some parameters that are always contained inside a rectangle.  The graph consists of curves and axes in black on a white background.  The rectangle is a box consisting of black lines and it contains black text on a white background.  I need to extract the box alone so I can run it through an OCR process to convert the key parameters inside the rectangle into text for other purposes.

Can anyone suggest a method, script or add-on for LiveCode that will help me extract a rectangle from its surrounding image?

Thanks.
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Peter Reid
Loughborough, UK