MatrixOp: TPAReduce1

function TPAReduce1(TPA:TPointArray): TPointArray;
var
  b:TBox;
  mat:TByteMatrix;
  edges:TPointArray;
begin
  B := GetTPABounds(TPA);
  OffsetTPA(TPA, Point(-B.x1, -B.y1));
  SetLength(Mat, B.height(),B.width());
  se.SetData(mat, TPA, TByteArray([1]));
  edges := se.TPAEdges(TPA);
  se.SetData(mat, edges, TByteArray([0]));
  Result := se.Indices(mat, 1, CMP_EQ);
  OffsetTPA(Result, Point(B.x1, B.y1));
end;