DETECT Edge document in iPhoneSDK

Question

I am looking at something like an attached image. How to implement this in iPhoneSDK.

Can anyone suggest me an open source API or Algorithm code for detecting the corners of a captured image of a document.

Some How, I got an open source API called OpenCV that recognizes Human Face very well . I want to use the same API if possible. Now the problem is how I can make changes to these static libraries according to my requirement for scanning the edges of a document. As an alternative,

How to define a square / rectangle object in a captured image?

Answer 1

openCV, :

http://www.sciweavers.org/books/opencv-open-source-computer-vision-reference-manual

10-6 :

CvContourScanner cvStartFindContours(IplImage* img, 
                                     CvMemStorage* storage, 
                                     int headerSize, 
                                     CvContourRetrievalMode mode, 
                                     CvChainApproxMethod method );

int cvFindContours( IplImage* img, 
                    CvMemStorage* storage,
                    CvSeq** firstContour, 
                    int headerSize=sizeof(CvContour),
                    CvContourRetrievalMode mode=CV_RETR_LIST,
                    CvChainApproxMethod method=CV_CHAIN_APPROX_SIMPLE );

, .

, OpenCV ios/iPhone, . XCode iOS:

http://www.eosgarden.com/en/opensource/opencv-ios/overview/

StackOverflow :

iPhone OpenCV