Beispiel #1
0
/**
 * cairo_matrix_invert:
 * @matrix: a @cairo_matrix_t
 *
 * Changes @matrix to be the inverse of it's original value. Not
 * all transformation matrices have inverses; if the matrix
 * collapses points together (it is <firstterm>degenerate</firstterm>),
 * then it has no inverse and this function will fail.
 *
 * Returns: If @matrix has an inverse, modifies @matrix to
 *  be the inverse matrix and returns %CAIRO_STATUS_SUCCESS. Otherwise,
 *  returns %CAIRO_STATUS_INVALID_MATRIX.
 **/
cairo_status_t
cairo_matrix_invert (cairo_matrix_t *matrix)
{
    /* inv (A) = 1/det (A) * adj (A) */
    double det;

    _cairo_matrix_compute_determinant (matrix, &det);

    if (det == 0)
        return CAIRO_STATUS_INVALID_MATRIX;

    _cairo_matrix_compute_adjoint (matrix);
    _cairo_matrix_scalar_multiply (matrix, 1 / det);

    return CAIRO_STATUS_SUCCESS;
}
Beispiel #2
0
/**
 * cairo_matrix_invert:
 * @matrix: a #cairo_matrix_t
 *
 * Changes @matrix to be the inverse of its original value. Not
 * all transformation matrices have inverses; if the matrix
 * collapses points together (it is <firstterm>degenerate</firstterm>),
 * then it has no inverse and this function will fail.
 *
 * Returns: If @matrix has an inverse, modifies @matrix to
 *  be the inverse matrix and returns %CAIRO_STATUS_SUCCESS. Otherwise,
 *  returns %CAIRO_STATUS_INVALID_MATRIX.
 **/
cairo_status_t
cairo_matrix_invert (cairo_matrix_t *matrix)
{
    double det;

    /* Simple scaling|translation matrices are quite common... */
    if (matrix->xy == 0. && matrix->yx == 0.) {
	matrix->x0 = -matrix->x0;
	matrix->y0 = -matrix->y0;

	if (matrix->xx != 1.) {
	    if (matrix->xx == 0.)
		return _cairo_error (CAIRO_STATUS_INVALID_MATRIX);

	    matrix->xx = 1. / matrix->xx;
	    matrix->x0 *= matrix->xx;
	}

	if (matrix->yy != 1.) {
	    if (matrix->yy == 0.)
		return _cairo_error (CAIRO_STATUS_INVALID_MATRIX);

	    matrix->yy = 1. / matrix->yy;
	    matrix->y0 *= matrix->yy;
	}

	return CAIRO_STATUS_SUCCESS;
    }

    /* inv (A) = 1/det (A) * adj (A) */
    det = _cairo_matrix_compute_determinant (matrix);

    if (! ISFINITE (det))
	return _cairo_error (CAIRO_STATUS_INVALID_MATRIX);

    if (det == 0)
	return _cairo_error (CAIRO_STATUS_INVALID_MATRIX);

    _cairo_matrix_compute_adjoint (matrix);
    _cairo_matrix_scalar_multiply (matrix, 1 / det);

    return CAIRO_STATUS_SUCCESS;
}