Function cvGetDiag

deps/opencv/modules/core/src/array.cpp:1383–1441

Selects array diagonal

// Selects array diagonal
CV_IMPL  CvMat*
cvGetDiag( const CvArr* arr, CvMat* submat, int diag )
{
    CvMat* res = 0;
    CvMat stub, *mat = (CvMat*)arr;
    int len, pix_size;

    if( !CV_IS_MAT( mat ))
        mat = cvGetMat( mat, &stub );

    if( !submat )
        CV_Error( CV_StsNullPtr, "" );

    pix_size = CV_ELEM_SIZE(mat->type);

    /*{
    int* refcount = mat->refcount;

    if( refcount )
        ++*refcount;

    cvDecRefData( submat );
    }*/

    if( diag >= 0 )
    {
        len = mat->cols - diag;

        if( len <= 0 )
            CV_Error( CV_StsOutOfRange, "" );

        len = CV_IMIN( len, mat->rows );
        submat->data.ptr = mat->data.ptr + diag*pix_size;
    }
    else
    {
        len = mat->rows + diag;

        if( len <= 0 )
            CV_Error( CV_StsOutOfRange, "" );

        len = CV_IMIN( len, mat->cols );
        submat->data.ptr = mat->data.ptr - diag*mat->step;
    }

    submat->rows = len;
    submat->cols = 1;
    submat->step = mat->step + (submat->rows > 1 ? pix_size : 0);
    submat->type = mat->type;
    if( submat->rows > 1 )
        submat->type &= ~CV_MAT_CONT_FLAG;
    else
        submat->type |= CV_MAT_CONT_FLAG;
    submat->refcount = 0;
    submat->hdr_refcount = 0;
    res = submat;

    return res;