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add area method for polygon geometries, and avoid compiler warnings about intializations with -03

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This commit is contained in:
Dane Springmeyer 2010-06-08 20:01:40 +00:00
parent 48921a412d
commit 13d192f255
1 changed files with 39 additions and 5 deletions
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38
include/mapnik/geometry.hpp
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@ -53,7 +53,8 @@ public:
box2d<double> envelope() const
{
box2d<double> result;
double x,y;
double x(0);
double y(0);
rewind(0);
for (unsigned i=0;i<num_points();++i)
{
@ -71,6 +72,7 @@ public:
}
virtual int type() const=0;
virtual double area() const=0;
virtual bool hit_test(value_type x,value_type y, double tol) const=0;
virtual void label_position(double *x, double *y) const=0;
virtual void move_to(value_type x,value_type y)=0;
@ -98,6 +100,11 @@ public:
return Point;
}
double area() const
{
return 0;
}
void label_position(double *x, double *y) const
{
*x = pt_.x;
@ -156,10 +163,31 @@ public:
return Polygon;
}
double area() const
{
unsigned i;
double sum = 0.0;
double x(0);
double y(0);
rewind(0);
double xs = x;
double ys = y;
for (unsigned i=0;i<num_points();++i)
{
double x0,y0;
vertex(&x0,&y0);
sum += x * y0 - y * x0;
x = x0;
y = y0;
}
return (sum + x * ys - y * xs) * 0.5;
}
box2d<double> envelope() const
{
box2d<double> result;
double x,y;
double x(0);
double y(0);
rewind(0);
for (unsigned i=0;i<num_points();++i)
{
@ -280,6 +308,12 @@ public:
{
return LineString;
}
double area() const
{
return 0;
}
void label_position(double *x, double *y) const
{
// calculate mid point on line string