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== polygon clipper

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+ don't build boost::geometry structures when :

 * input bounding box is contained by clipping box (return original verticies)
 * input box is outside of clipping box ( return SEG_END)
This commit is contained in:
artemp 2013-10-10 13:44:32 +01:00
parent 7f035f9226
commit 07a6fee1ed
1 changed files with 40 additions and 5 deletions
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45
include/mapnik/polygon_clipper.hpp
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@ -95,22 +95,33 @@ struct polygon_clipper
typedef model::polygon<mapnik::coord2d> polygon_2d;
typedef std::deque<polygon_2d> polygon_list;
enum
{
clip = 1,
no_clip = 2,
ignore = 3
} state_;
polygon_clipper(Geometry & geom)
: clip_box_(),
: state_(clip),
clip_box_(),
geom_(geom)
{
}
polygon_clipper(box2d<double> const& clip_box, Geometry & geom)
: clip_box_(clip_box),
geom_(geom)
:state_(clip),
clip_box_(clip_box),
geom_(geom),
{
init();
}
void set_clip_box(box2d<double> const& clip_box)
{
state_ = clip;
clip_box_ = clip_box;
init();
}
@ -122,18 +133,42 @@ struct polygon_clipper
void rewind(unsigned path_id)
{
output_.rewind(path_id);
if (state_ == clip) output_.rewind(path_id);
else geom_.rewind(path_id);
}
unsigned vertex (double * x, double * y)
{
return output_.vertex(x,y);
switch (state_)
{
case clip:
return output_.vertex(x,y);
case no_clip:
return geom_.vertex(x,y);
case ignore:
return SEG_END;
}
}
private:
void init()
{
geom_.rewind(0);
box2d<double> bbox = geom_.envelope();
if (clip_box_.contains(bbox))
{
// shortcut to original geometry (no-clipping)
state_ = no_clip;
return;
}
else if (!clip_box_.intersects(bbox))
{
// polygon is outside of clipping box
state_ = ignore;
return;
}
polygon_2d subject_poly;
double x,y;
double prev_x, prev_y;