How to access a single object in a metafile

Problem/Question/Abstract:

How to access a single object in a metafile

Answer:

Below is an example of getting metafile information and enumerating each metafile record :

function MyEnhMetaFileProc(DC: HDC; {handle to device context}
  lpHTable: PHANDLETABLE; {pointer to metafile handle table}
  lpEMFR: PENHMETARECORD; {pointer to metafile record}
  nObj: integer; {count of objects}
  TheForm: TForm1): integer; stdcall;
begin
  {draw the metafile record}
  PlayEnhMetaFileRecord(dc, lpHTable^, lpEMFR^, nObj);
  {set to zero to stop metafile enumeration}
  result := 1;
end;

procedure TForm1.Button1Click(Sender: TObject);
var
  MyMetafile: TMetafile;
  lpENHMETAHEADER: PENHMETAHEADER; {extra metafile info}
  lpENHMETAHEADERSIZE: DWORD;
  NumMetaRecords: DWORD;
begin
  {Create a metafile}
  MyMetafile := TMetafile.Create;
  with TMetafileCanvas.Create(MyMetafile, 0) do
  try
    Brush.Color := clRed;
    Ellipse(0, 0, 100, 100);
    Ellipse(100, 100, 200, 200);
    Ellipse(200, 200, 300, 300);
    Ellipse(300, 300, 400, 400);
    Ellipse(400, 400, 500, 500);
    Ellipse(500, 500, 600, 600);
  finally
    Free;
  end;
  {we might as well get some extra metafile info}
  lpENHMETAHEADERSIZE := GetEnhMetaFileHeader(MyMetafile.Handle, 0, nil);
  NumMetaRecords := 0;
  if (lpENHMETAHEADERSIZE > 0) then
  begin
    GetMem(lpENHMETAHEADER, lpENHMETAHEADERSIZE);
    GetEnhMetaFileHeader(MyMetafile.Handle, lpENHMETAHEADERSIZE, lpENHMETAHEADER);
    {Here is an example of getting number of metafile records}
    NumMetaRecords := lpENHMETAHEADER^.nRecords;
    {enumerate the records}
    EnumEnhMetaFile(Canvas.Handle, MyMetafile.Handle, @MyEnhMetaFileProc, self,
      Rect(0, 0, 600, 600));
    FreeMem(lpENHMETAHEADER, lpENHMETAHEADERSIZE);
  end;
  MyMetafile.Free;
end;