How can I select a rectangular ROI from an image automatically?

I need to extract the rectangular area automatically. It would be appreciated if anybody help me in this regard.

[KSSV]

Give a try with ocr once.

[Sudipto Chaki]

I don't understand your method clearly. Would you please elaborate?

[Image Analyst]

Look at the links on the right side of this page if it's really the numbers that you want, instead of a box.

[Sudipto Chaki]

I need the box with digits for my ROI image