Получение captcha и отправка post запроса

procedure TForm1.btn2Click(Sender: TObject);
var
html:WideString;
Stream:TStream;
png:TPNGObject;
begin
try
png:=TPNGObject.Create;
Stream:=TStringStream.Create(IdHTTP1.Get('http://api.***.ru/captcha'));
png.LoadFromStream(Stream);
Image1.Picture.Assign(png);
Stream.Free;
png.Free;
except
on e:Exception do
begin
png.Free;
Stream.Free;
end;
end;
end;

procedure TForm1.btn1Click(Sender: TObject);
var
  Data:TStringList;
  S:WideString;
begin
 
 Data:=TStringList.Create; 
 
 //äàëåå äîáàâëÿåì äàííûå äëÿ POST çàïðîñà
 Data.Add('first_name='+medt1.Text);
 Data.Add('email='+medt2.Text);
 Data.Add('password='+medt3.Text);
 Data.Add('password_confirm='+medt3.Text);
 Data.Add('captcha='+edt1.Text);
 Data.Add('agree=agree');
 IdHTTP1.HandleRedirects:=true;
  with IdHTTP1.Request do
  begin
    Host:='api.***.ru';
    UserAgent := 'Mozilla/5.0 (Windows NT 6.1; rv:18.0) Gecko/20100101 Firefox/18.0';
    Accept := 'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8';
    AcceptLanguage := 'ru-RU,ru;q=0.8,en-US;q=0.5,en;q=0.3';
    AcceptEncoding:='gzip, deflate';
    Referer:='http://www.***.ru/zakazat?first_name='+medt1.Text+'&email='+medt2.Text+'&password='+medt3.Text+'&password_confirm='+medt3.Text+'&captcha='+edt1.Text+'&agree=agree';
  end;
 S:=IdHTTP1.Post('http://api.***.ru/v-2/client-register', Data); 
 Data.Free; 
 mmo1.text:=Utf8ToAnsi(S);
end;