INFO: Windows Metafile Functions & Aldus Placeable Metafiles (66949)

SUMMARY

Many Windows-based applications import or export Windows metafiles in a format known as the Aldus Placeable Metafile (APM) format. In this format, these metafiles cannot be used with the Windows metafile functions such as GetMetaFile(), CopyMetaFile(), PlayMetaFile(), and so on. To use these metafiles, the APM header must be removed from the metafile and the remaining metafile bits must be written to a newly created metafile.

MORE INFORMATION

The APM header is 22 bytes in length and is defined as follows:

   typedef struct
     {
     DWORD   key;
     HANDLE  hmf;
     RECT    bbox;
     WORD    inch;
     DWORD   reserved;
     WORD    checksum;
     } APMFILEHEADER;

The following code fragment demonstrates how to create a memory-based Windows metafile from an Aldus Placeable Metafile that will work with the metafile functions provided by Windows.

The Placeable Windows Metafiles are also documented on pages 26-27 of the "Programmer's Reference, Volume 4: Resources" manual from the Windows 3.1 SDK documentation.

Sample Code

   BOOL RenderAPM (fh)
   int   fh; // a file handle to the APM metafile is passed in
   {
       HANDLE           hData;
       LPSTR            lpData;
       DWORD            OffsetToMeta;
       METAHEADER       mfHeader;
       APMFILEHEADER    APMHeader;

       OffsetToMeta = sizeof(APMHeader);

   // Seek to beginning of file and read APM header
       _llseek(fh, 0, 0);
       if (!_lread(fh, (LPSTR)&APMHeader, sizeof(APMFILEHEADER)))
           // Error in reading the file
           return(FALSE);

   // Return to read metafile header
       _llseek(fh, OffsetToMeta, 0);
       if (!_lread(fh, (LPSTR)&mfHeader, sizeof(METAHEADER)))
           // Error in reading
           return(FALSE);

   // Allocate memory for memory based metafile
       if (!(hData = GlobalAlloc(GHND, (mfHeader.mtSize * 2L))))
           return(FALSE);
   // Were we successful?
       if (!(lpData = GlobalLock(hData)))
       {
           // Error in allocation
           GlobalFree(hData);
           return(FALSE);
       }

   // Read metafile bits
       _llseek(fh, OffsetToMeta, 0);
       if (!_lread(fh, lpData, (mfHeader.mtSize * 2L)))
       {
           // Error in reading
           GlobalUnlock(hData);
           GlobalFree(hData);
           return(FALSE);
       }

   // Create the METAFILE with the bits we read in.
       if (!(hMF = SetMetaFileBits(hData)))
           return(FALSE);

       GlobalUnlock(hData);

   // Close the APM file
       _lclose(fh);

   // Return success
       return(TRUE);
   }