CGAL 4.7 - 2D Snap Rounding: CGAL::Snap_rounding_traits_2< Kernel > Class Template Reference

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CGAL 4.7 - 2D Snap Rounding

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CGAL::Snap_rounding_traits_2< Kernel > Class Template Reference
2D Snap Rounding Reference

`#include <CGAL/Snap_rounding_traits_2.h>`

## Definition

The class `Snap_rounding_traits_2<Kernel>` is a model of the `SnapRoundingTraits_2` concept, and is the only traits class supplied with the package.

This class should be instantiated with an exact geometric kernel that conforms to the CGAL kernel-concept, such as the `Exact_predicates_exact_constructions_kernel`, or `Cartesian<Gmpq>`.

This geometric kernel must provide an (arbitrary-precision) rational number type (`FT`), `Point_2`, `Segment_2` and `Iso_rectangle_2`. It should be possible to cast numbers of the number type `FT` to double-precision representation. That is, the function `CGAL::to_double(FT)` must be supported.

The `CGAL::to_double()` function is used to implement the operation that rounds the coordinates of a point to a center of a pixel. This operation is one of the traits-concept requirement. The coordinates are converted to double, rounded down to the nearest grid point, and finally adjusted to lie on a center of a pixel. Notice that if `CGAL::to_double()` returns the closet value, then when it rounds up a given coordinate, the resulting ISR, may be imprecise, and the distance between some vertex and a non-incident edge can be slightly less than the guaranteed half-the width-of-a-pixel.

Is Model Of:
  `SnapRoundingTraits_2`

Examples:
  Snap_rounding_2/snap_rounding.cpp, and Snap_rounding_2/snap_rounding_to_integer.cpp.