void printMatrix( char *disp, CvMat *matrix ) {
    for ( int y=0; y < matrix->height; y++ ) {
        for ( int x=0; x < matrix->width; x++ ) {
            printf( disp, cvmGet( matrix, y, x ) ); 
        }
        printf( "\n" );
    }
    printf( "\n" );
}