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OpenCV- An overview Intel ® OPEN SOURCE COMPUTER VISION LIBRARY

OpenCV- An overview Intel ® OPEN SOURCE COMPUTER VISION LIBRARY. Goals. Develop a universal toolbox for research and development in the field of Computer Vision. Features. Image data manipulation allocation, release, copying, setting, conversion Image and video I/O

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OpenCV- An overview Intel ® OPEN SOURCE COMPUTER VISION LIBRARY

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  1. OpenCV- An overview Intel® OPEN SOURCE COMPUTER VISION LIBRARY

  2. Goals • Develop a universal toolbox for research and development in the field of Computer Vision

  3. Features • Image data manipulation • allocation, release, copying, setting, conversion • Image and video I/O • file and camera based input, image/video file output • Matrix and vector manipulation, and linear algebra routines • products, solvers, eigenvalues, SVD • Various dynamic data structures • lists, queues, sets, trees, graphs • Basic image processing • filtering, edge detection, corner detection, sampling and interpolation, color conversion, morphological operations, histograms, image pyramids

  4. Features (cont.) • Structural analysis • connected components, contour processing, distance transform, various moments, template matching, Hough transform, polygonal approximation, line fitting, ellipse fitting, Delaunay triangulation • Camera calibration • finding and tracking calibration patterns, calibration, fundamental matrix estimation, homography estimation, stereo correspondence • Motion analysis • optical flow, motion segmentation, tracking • Object recognition • eigen-methods, HMM • Basic GUI • display image/video, keyboard and mouse handling, scroll-bars • Image labeling • line, conic, polygon, text drawing

  5. Modules • OpenCV Functionality • more than 350 algorithms • Cxcore • Data structures and linear algebra support. • cv • Main OpenCV functions. • Cvaux • Auxiliary (experimental) OpenCV functions. • Highgui • GUI functions.

  6. How do I download it? • http://www.intel.com/technology/computing/opencv/index.htm • Version: beta 5

  7. Forums & Resources • http://opencvlibrary.sourceforge.net/ • http://groups.yahoo.com/group/OpenCV/ • http://www.cs.iit.edu/~agam/cs512/lect-notes/opencv-intro/index.html • Books • Gary R. Bradski, Vadim Pisarevsky, and Jean-Yves Bouguet, Open Source Computer Vision Library, Springer, 1st ed. (June, 2006). • Toturial • http://nchc.dl.sourceforge.net/sourceforge/opencvlibrary/ippocv.pdf

  8. System requirement • Platforms: • Win9x/WinNT/Win2000 • C++ Compiler(Visual C++ 6.0,Intel C++ Compiler 5.x,Borland C++ 5.5, Mingw GNU C/C++ 2.95.3 are included ) for core libraries • Matlab • Visual C++ to build the most of demos

  9. Settings- An example in VC • Library: project->setting->link • cv.lib cvaux.lib highgui.lib cxcore.lib • Directories • Include • C:\PROGRAM FILES\OPENCV\CV\INCLUDE • C:\PROGRAM FILES\OPENCV\CVAUX\INCLUDE • C:\PROGRAM FILES\OPENCV\OTHERLIBS\HIGHGUI • C:\PROGRAM FILES\OPENCV\CXCORE\INCLUDE • Library • C:\PROGRAM FILES\OPENCV\LIB • FilePathName • C:\PROGRAM FILES\OPENCV\bin • Include in programs • #include "cv.h“, "cvaux.h“, "highgui.h“, "cxcore.h"

  10. Outline of this course • Basic structures & functions in OpenCV • HighGUI & I/O • Image processing • Structural analysis (contour, geometry) • AdaBoost & object detection • Object recognition • Motion analysis & object tracking • Camera calibration & 3D reconstruction

  11. Today’s outline • Basic structures • Operations on arrays • Dynamic structures • Drawing functions • Miscellaneous functions • Error handling

  12. Basic structures (1) • CvPoint typedef struct CvPoint { int x; /* x-coordinate, usually zero-based */ int y; /* y-coordinate, usually zero-based */ } CvPoint; • Usage CvPoint P1; P1.x = 10; P1.y = 2; • CvPoint2D32f, CvPoint2D64f, CvPoint3D32f, CvPoint3D64f

  13. Basic structures (2) • CvSize typedef struct CvSize { int width; /* width of the rectangle */ int height; /* height of the rectangle */ } CvSize; • CvSize2D32f • CvRect • offset and size of a rectangle • CvScalar • a container for 1-, 2-, 3- or 4-tuples of numbers

  14. Basic structures (3) • CvTermCriteria • Termination criteria for iterative algorithms typedef struct CvTermCriteria { int type; /* a combination of CV_TERMCRIT_ITER and CV_TERMCRIT_EPS */ int max_iter; /* maximum number of iterations */ double epsilon; /* accuracy to achieve */ } CvTermCriteria; • CvArr • Arbitrary array • CvMat, IplImage, CvSeq

  15. Basic structures (4) • CvMat typedef struct CvMat { int type; /* CvMat signature (CV_MAT_MAGIC_VAL), element type and flags */ int step; /* full row length in bytes */ int* refcount; /* underlying data reference counter */ union { uchar* ptr; short* s; int* i; float* fl; double* db; } data; /* data pointers */ #ifdef __cplusplus union { int rows; int height; }; union { int cols; int width; }; #else int rows; /* number of rows */ int cols; /* number of columns */ #endif } CvMat; • CvMatND, CvSparseMat

  16. Basic structures (5) • Usage of CvMat CvMat* cvCreateMat( int rows, int cols, int type ); void cvReleaseMat( CvMat** mat ); void cvSet2D( CvArr* arr, int idx0, int idx1, CvScalar value ); CvScalar cvGet2D( const CvArr* arr, int idx0, int idx1 ); CvMat* M = cvCreateMat(2, 2, CV_32F); cvSet2D(M, 0, 0, cvScalar(1)); cvSet2D(M, 0, 1, cvScalar(2)); cvSet2D(M, 1, 0, cvScalar(3)); cvSet2D(M, 1, 1, cvScalar(4)); i = cvGet2D(M, 0, 0).val[0]; j = cvGet2D(M, 0, 1).val[0];  i = 1, j = 2. cvReleaseMat(&M);

  17. Basic structures (6) • Usage of CvMat CvMat* cvInitMatHeader( CvMat* mat, int rows, int cols, int type, void* data=NULL, int step=CV_AUTOSTEP ); void cvMatMulAdd( const CvArr* A, const CvArr* B, const CvArr* C, CvArr* D );[D=A*B+C] double a[] = { 1, 2, 3, 4 5, 6, 7, 8, 9, 10, 11, 12 }; double b[] = { 1, 5, 9, 2, 6, 10, 3, 7, 11, 4, 8, 12 }; double c[9]; CvMat Ma, Mb, Mc ; cvInitMatHeader( &Ma, 3, 4, CV_64FC1, a ); cvInitMatHeader( &Mb, 4, 3, CV_64FC1, b ); cvInitMatHeader( &Mc, 3, 3, CV_64FC1, c ); cvMatMulAdd( &Ma, &Mb, 0, &Mc );

  18. Basic structures (7) IplImage: IPL image header typedef struct _IplImage { int nSize; /* sizeof(IplImage) */ int nChannels; /* Most of OpenCV functions support 1,2,3 or 4 channels */ int depth; /* pixel depth in bits: IPL_DEPTH_8U, IPL_DEPTH_8S, IPL_DEPTH_16U, IPL_DEPTH_16S, IPL_DEPTH_32S, IPL_DEPTH_32F and IPL_DEPTH_64F are supported */ int dataOrder; /* 0 - interleaved color channels, 1 - separate color channels. cvCreateImage can only create interleaved images */ int origin; /* 0 - top-left origin, 1 - bottom-left origin (Windows bitmaps style) */ int width; /* image width in pixels */ int height; /* image height in pixels */ struct _IplROI *roi;/* image ROI. when it is not NULL, this specifies image region to process */ int imageSize; /* image data size in bytes */ char *imageData; /* pointer to aligned image data */ int widthStep; /* size of aligned image row in bytes */ char *imageDataOrigin; /* pointer to a very origin of image data (not necessarily aligned) - it is needed for correct image deallocation */ } IplImage;

  19. Basic structures (8) • Usage of IplImage IplImage* cvCreateImage( CvSize size, int depth, int channels ); void cvReleaseImage( IplImage** image ); IplImage *src_img; src_img = cvCreateImage(imgSize, IPL_DEPTH_8U, 1); cvReleaseImage( src_img );

  20. Operations on arrays (1) • CloneImage: Makes a full copy of image • IplImage* cvCloneImage( const IplImage* image ); • SetImageROI • void cvSetImageROI( IplImage* image, CvRect rect ); • GetImageROI • CvRect cvGetImageROI( const IplImage* image ); • ResetImageROI: Releases image ROI • void cvResetImageROI( IplImage* image ); • SetImageCOI: Sets channel of interest to given value • void cvSetImageCOI( IplImage* image, int coi ); • coi = 0 means that all channels are selected. • GetImageCOI: Returns index of channel of interest • int cvGetImageCOI( const IplImage* image );

  21. Operations on arrays (2) • CreateMat/CreateMatHeader: Creates new matrix (header) • CvMat* cvCreateMat( int rows, int cols, int type ); • ReleaseMat • void cvReleaseMat( CvMat** mat ); • CloneMat: Creates matrix copy • CvMat* cvCloneMat( const CvMat* mat ); • CreateData: Allocates array data • Void cvCreateData( CvArr* arr ); • GetRow: Returns array row • cvGetRow( const CvArr* arr, CvMat* submat, int row ); • GetCol: Returns array column • cvGetCol( const CvArr* arr, CvMat* submat, int col ); • GetDiag: Returns one of array diagonals • cvGetDiag( const CvArr* arr, CvMat* submat, int diag=0 ); • GetSize: Returns size of matrix or image ROI • CvSize cvGetSize( const CvArr* arr ); • ...

  22. Operations on arrays (3) • Copy: Copies one array to another • cvCopy( const CvArr* src, CvArr* dst, const CvArr* mask=NULL ); • Set: Sets every element of array to given value • cvSet( CvArr* arr, CvScalar value, const CvArr* mask=NULL ); • SetZero: Clears the array • cvSetZero( CvArr* arr ); • Reshape: Changes shape of matrix/image without copying data • CvMat* cvReshape( const CvArr* arr, CvMat* header, int new_cn, int new_rows=0 ); • Image example (from color to gray-level) IplImage* color_img = cvCreateImage( cvSize(320,240), IPL_DEPTH_8U, 3 ); CvMat gray_mat_hdr; IplImage gray_img_hdr, *gray_img; cvReshape( color_img, &gray_mat_hdr, 1 ); gray_img = cvGetImage( &gray_mat_hdr, &gray_img_hdr ); • Matrix example (from a 3*3 matrix to a 1*9 vector) CvMat* mat = cvCreateMat( 3, 3, CV_32F ); CvMat row_header, *row; row = cvReshape( mat, &row_header, 0, 1 ); • Flip, Split, Merge

  23. Operations on arrays (4) • ConvertScale, Add, AddWeighted, Sub, Mul, Div, And, Or, Xor, Cmp, InRange, Max, Min, Sum, Avg, Norm, DotProduct, CrossProduct, Transform, MulTransposed, Trace, Det, Invert, Mahalonobis … • Solve: Solves linear system or least-squares problem • int cvSolve( const CvArr* A, const CvArr* B, CvArr* X, int method=CV_LU, CV_SVD ); • AX = B • EigenVV: Computes eigenvalues and eigenvectors of symmetric matrix • void cvEigenVV( CvArr* mat, CvArr* evects, CvArr* evals, double eps=0 );

  24. Dynamic structures (1) • Memory storages • CvMemStorage typedef struct CvMemStorage { struct CvMemBlock* bottom;/* first allocated block */ struct CvMemBlock* top; /* the current memory block – top of the stack */ struct CvMemStorage* parent; /* borrows new blocks from */ int block_size; /* block size */ int free_space; /*free space in the top block (in bytes)*/ } CvMemStorage; free_space block_size bottom top

  25. Dynamic structures (2) • CvMemBlock: Memory storage block typedef struct CvMemBlock { struct CvMemBlock* prev; struct CvMemBlock* next; } CvMemBlock; • CvMemStoragePos: Memory storage position typedef struct CvMemStoragePos { CvMemBlock* top; int free_space; } CvMemStoragePos;

  26. Dynamic structures (3) • CreateMemStorage: Creates memory storage CvMemStorage* cvCreateMemStorage( int block_size ); • MemStorageAlloc: Allocates memory buffer in the storage void* cvMemStorageAlloc( CvMemStorage* storage, size_t size ); • ReleaseMemStorage: Releases memory storage CvMemStorage* cvReleaseMemStorage(CvMemStorage** storage); • ClearMemStorage: Clears memory storage void cvClearMemStorage( CvMemStorage* storage );

  27. Dynamic structures (4) • CreateChildMemStorage: Creates child memory storage CvMemStorage* cvCreateChildMemStorage( CvMemStorage* parent ); • It is similar to memory storage except for the differences in the memory allocation/deallocation mechanism. • Require a new block: get it from the parent. • The first unoccupied parent block available is taken & excluded from the parent block list. • If no blocks are available, the parent either allocates a block or borrows one from its own parent. • Release or clear: return all blocks to the parent. Dynamic data processing without using child storage Dynamic data processing using a child storage

  28. Dynamic structures (5) • CvSeq: Growable sequence of elements #define CV_SEQUENCE_FIELDS() int flags; /* micsellaneous flags */ int header_size; /* size of sequence header */ struct CvSeq* h_prev; /* previous sequence */ struct CvSeq* h_next; /* next sequence */ struct CvSeq* v_prev; /* 2nd previous sequence */ struct CvSeq* v_next; /* 2nd next sequence */ int total; /* total number of elements */ int elem_size;/* size of sequence element in bytes */ char* block_max;/* maximal bound of the last block */ char* ptr; /* current write pointer */ int delta_elems; /* how many elements allocated when the sequence grows (sequence granularity) */ CvMemStorage* storage; /* where the seq is stored */ CvSeqBlock* free_blocks; /* free blocks list */ CvSeqBlock* first; /* pointer to the first sequence block */ typedef struct CvSeq { CV_SEQUENCE_FIELDS() } CvSeq; • Operations of CvSeq

  29. Dynamic structures (6) • CvSet • Collection of nodes • CvGraph • Oriented or unoriented weigted graph • CV_TREE_NODE_FIELDS • For a tree node type declaration

  30. Drawing functions • CV_RGB, cvLine, cvRectangle, cvCircle, cvEllipse, cvFillPoly, cvFillConvexPoly, cvPolyLine, cvDrawContours. • cvInitFont, cvPutText, cvGetTextSize.

  31. Miscellaneous functions • cvKMeans2() • Splits set of vectors by given number of clusters void cvKMeans2( const CvArr* samples, int cluster_count, CvArr* labels, CvTermCriteria termcrit );

  32. Example of KMeans2 C-code

  33. Error handling (1) • There are no return error codes • It raises an error using CV_ERROR macro that calls cvError • int cvError( int status, const char* func_name, const char* err_msg, const char* file_name, int line );

  34. Error handling (2) #define __BEGIN__ { #define __END__ goto exit; exit: ; } /* proceeds to "resource release" stage */ #define EXIT goto exit /* Declares locally the function name for CV_ERROR() use */ #define CV_FUNCNAME( Name ) static char cvFuncName[] = Name /* Raises an error within the current context */ #define CV_ERROR( Code, Msg ) { cvError( (Code), cvFuncName, Msg, __FILE__, __LINE__ ); EXIT; } /* Checks status after calling CXCORE function */ #define CV_CHECK() { if( cvGetErrStatus() < 0 ) CV_ERROR( CV_StsBackTrace, "Inner function failed." ); } /* Provies shorthand for CXCORE function call and CV_CHECK() */ #define CV_CALL( Statement ) { Statement; CV_CHECK(); } /* Checks some condition in both debug and release configurations */ #define CV_ASSERT( Condition ) { if( !(Condition) ) CV_ERROR( CV_StsInternal, "Assertion: " #Condition " failed" ); }

  35. Error handling (3) • Three modes of error handling • Leaf: The program is terminated after error handler is called. This is the default value. • Parent: The program is not terminated, but the error handler is called. • Silent: Similar to Parent mode, but no error handler is called. • SetErrMode: #define CV_ErrModeLeaf 0 #define CV_ErrModeParent 1 #define CV_ErrModeSilent 2 int cvSetErrMode( int mode ); • Check error code int cvGetErrStatus( void );

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