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correct the calculation of the error bound.

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Bertram Felgenhauer 2005-08-22 16:50:30 +00:00
parent c0905759b0
commit 9883104290
2 changed files with 11 additions and 14 deletions
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5
ChangeLog
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@ -1,3 +1,8 @@
2005-08-22 Bertram Felgenhauer <int-e@gmx.de>
* src/cairo-arc.c (_arc_segments_needed): correct the calculation of
the error bound.
2005-08-22 Bertram Felgenhauer <int-e@gmx.de>
* src/cairo-pen.c (_cairo_pen_vertices_needed): use new function.

20
src/cairo-arc.c
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@ -100,27 +100,19 @@ _arc_max_angle_for_tolerance_normalized (double tolerance)
return angle;
}
/* XXX: The computation here if bogus. Correct math (with proof!) is
* available in _cairo_pen_vertices_needed. */
static int
_arc_segments_needed (double angle,
double radius,
cairo_matrix_t *ctm,
double tolerance)
{
double l1, l2, lmax;
double max_angle;
double major_axis, max_angle;
_cairo_matrix_compute_eigen_values (ctm, &l1, &l2);
l1 = fabs (l1);
l2 = fabs (l2);
if (l1 > l2)
lmax = l1;
else
lmax = l2;
max_angle = _arc_max_angle_for_tolerance_normalized (tolerance / (radius * lmax));
/* the error is amplified by at most the length of the
* major axis of the circle; see cairo-pen.c for a more detailed analysis
* of this. */
major_axis = _cairo_matrix_transformed_circle_major_axis (ctm, radius);
max_angle = _arc_max_angle_for_tolerance_normalized (tolerance / major_axis);
return (int) ceil (angle / max_angle);
}