How to convert a PDF to GIF,BMP or JPG?

var pdf : TWPViewPDF;
    meta : TMetafile;
    page : Integer;
    bit : TBitmap;
    jpeg: TJPEGImage;
    path : String;
begin
  path := ExtractFilePath(Application.EXEName);
  // Set WPViewPDF DLL name:
  WPViewPDFDLLNAME := 'wPDFView01.dll';
  // Install PDF License
  WPPDFViewerStart('LICNAME','LICKEY',LICCODE);


  // Create a Viewer
  pdf := TWPViewPDF.Create(nil);
  // Currently we need a parent
  pdf.SetBounds(-10,-10,1,1);
  pdf.Parent := Self;
  page := StrToIntDef( PageNr.Text, 1);
  try
    pdf.LoadFromFile(FileName.Text);
      meta := pdf.GetMetafile(page);
      if meta<>nil then
      try
        if (FormatName.Text='BMP') or (FormatName.Text='JPEG') then
        begin
          bit := TBitmap.Create;
          try
            bit.Width := Round(meta.MMWidth /10);
            bit.Height := Round(meta.MMHeight /10);
            bit.Canvas.StretchDraw(bit.Canvas.ClipRect, meta);
            if FormatName.Text='JPEG' then
            begin
              jpeg := TJPEGImage.Create;
              try
                jpeg.Assign(bit);
                jpeg.Compress;
                jpeg.SaveToFile(path + PageNr.Text + '.JPG');
                Image1.Picture.Assign(jpeg);
              finally
                jpeg.Free;
              end;
            end else
            begin
               Image1.Picture.Assign(bit);
               bit.SaveToFile(path + PageNr.Text + '.BMP');
            end;
          finally
            bit.Free;
          end;
        end
        else
        begin
           Image1.Picture.Assign(meta);
           meta.SaveToFile(path + PageNr.Text + '.EMF');
        end;
      finally
        meta.Free;
      end;
  finally
    pdf.Parent := nil;
    pdf.Free;
  end;
end;