Computer vision, Coupon code detection, sugested algorithms The telecommunication operator in my country has coupons that used to recharge the balance



I want to develop an Android application, that with the camera can take the scratched number and recognize and automatic recharge.

I think finding the number box, and latter preform an OCR or a pattern match in because are numbers only

I'm new in computer vision I set the environment and test some opencv ups, but I'm losing witch algorithms or sequence of algorithms may use to achieve that I want Exist segmentation, feature detection, blob detection, ... template match but the image maybe rotates scale because the use of the camera

And I'm lose I wonder if exist one algorithm to find the 4 extreme points of a coupon in one image from here I know how to proceed until the OCR part I don't want the code to do it of course

What I want is a simple clue, answer like you may use X algorithm to have Y result

Thanks and sorry for my english
You may try an OCR detector like Teseract with OpenCV:

https://github.com/tesseract-ocr

Train the Teseract algorithm with text samples obtained from the numbers you want to detect and it will work.

EDIT: If you want a similar implementation of what you want you may check this:

http://answers.opencv.org/question/10985/how-can-i-determine-the-location-of-lcdled-display-in-an-image-with-opencv-and-perl/