设三个顶点为(x1,y1),(x2,y2),(x3,y3)
procedure ...;
var
r:HRGN;
begin
with canvas do
begin
BeginPath(Canvas.Handle);
moveto(x1,y1);
linrto(x2,y2);
linrto(x3,y3);
linrto(x1,y1);
EndPath(Canvas.Handle);
PathToRgn(r);
FillRgn(Canvas.Handle,r,Canvas.Brush.handle);
end;