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{converts an area of white pixels in one color}
procedure TForm1.Convert(X,Y,Color: integer);
var Queue: TConvArray; //queue used to avoid a stack overflow
begin
 SetLength(Queue,1);
 Queue[0].X:=X;
 Queue[0].Y:=Y;

 while Length(Queue)>0 do
   begin

      X:=Queue[High(Queue)].X;
      Y:=Queue[High(Queue)].Y;
      SetLength(Queue,Length(Queue)-1);

       if (Pix[X,Y]=clWhite)then
         begin
          Pix[X,Y]:=Color;

          if (X+1>=0)and(Y>=0)and(X+1<=High(Pix))and(Y<=High(Pix[0]))then
            if Pix[X+1,Y]=clWhite then
              begin
                SetLength(Queue,Length(Queue)+1);
                Queue[High(Queue)].X:=X+1;
                Queue[High(Queue)].Y:=Y;
              end;

          if (X>=0)and(Y+1>=0)and(X<=High(Pix))and(Y+1<=High(Pix[0]))then
            if Pix[X,Y+1]=clWhite then
              begin
                SetLength(Queue,Length(Queue)+1);
                Queue[High(Queue)].X:=X;
                Queue[High(Queue)].Y:=Y+1;
              end;

          if (X-1>=0)and(Y>=0)and(X-1<=High(Pix))and(Y<=High(Pix[0]))then
            if Pix[X-1,Y]=clWhite then
              begin
                SetLength(Queue,Length(Queue)+1);
                Queue[High(Queue)].X:=X-1;
                Queue[High(Queue)].Y:=Y;
              end;

          if (X>=0)and(Y-1>=0)and(X<=High(Pix))and(Y-1<=High(Pix[0]))then
            if Pix[X,Y-1]=clWhite then

              begin
                SetLength(Queue,Length(Queue)+1);
                Queue[High(Queue)].X:=X;
                Queue[High(Queue)].Y:=Y-1;
              end;
        end;
   end;
end;