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[matrix] Optimise invert for simple scaling|translation matrices.

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The matrix is quite often just a simple scale and translate (or even
identity!). For this class of matrix, we can skip the full adjoint
rearrangement and determinant calculation and just compute the inverse
directly.
This commit is contained in:
Chris Wilson 2008-10-26 12:53:29 +00:00
parent 74876b00cd
commit 0d0c6a199c
1 changed files with 25 additions and 1 deletions
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26
src/cairo-matrix.c
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@ -525,9 +525,33 @@ _cairo_matrix_compute_adjoint (cairo_matrix_t *matrix)
cairo_status_t
cairo_matrix_invert (cairo_matrix_t *matrix)
{
/* inv (A) = 1/det (A) * adj (A) */
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))