Difference between revisions of "Geometry in Pascal"
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==Checking if a point is inside a polygon (integer version)== | ==Checking if a point is inside a polygon (integer version)== | ||
Revision as of 17:37, 27 September 2010
Checking if a point is inside a polygon (integer version)
<delphi> // The function will return True if the point x,y is inside the polygon, or // False if it is not. // // Original C code: http://www.visibone.com/inpoly/inpoly.c.txt // // Translation from C by Felipe Monteiro de Carvalho // // License: Public Domain function IsPointInPolygon(AX, AY: Integer; APolygon: array of TPoint): Boolean; var
xnew, ynew: Cardinal; xold,yold: Cardinal; x1,y1: Cardinal; x2,y2: Cardinal; i, npoints: Integer; inside: Integer = 0;
begin
Result := False;
npoints := Length(APolygon);
if (npoints < 3) then Exit;
xold := APolygon[npoints-1].X;
yold := APolygon[npoints-1].Y;
for i := 0 to npoints - 1 do
begin
xnew := APolygon[i].X;
ynew := APolygon[i].Y;
if (xnew > xold) then
begin
x1:=xold;
x2:=xnew;
y1:=yold;
y2:=ynew;
end
else
begin
x1:=xnew;
x2:=xold;
y1:=ynew;
y2:=yold;
end;
if (((xnew < AX) = (AX <= xold)) // edge "open" at left end
and ((AY-y1)*(x2-x1) < (y2-y1)*(AX-x1))) then
begin
inside := not inside;
end;
xold:=xnew;
yold:=ynew;
end;
Result := inside <> 0;
end; </delphi>
