How To Draw on a Pre-Existing Enhanced Metafile (230675)

MORE INFORMATION

1. Load the source EMF using GetEnhMetaFile().
2. Calculate the size of the source EMF from its header.
3. Create a new EMF DC that is the same size as the original.
4. Play the source EMF on to the new DC.

// This function returns an EMF HDC, on which has already been drawn the contents of the source EMF.
HDC MakeNewWritableMetafile( LPTSTR szSourceFileName, LPTSTR szTargetFileName )
{
	HENHMETAFILE	hSourceEMF;
	HDC				hTargetDC, hRefDC;
	ENHMETAHEADER	emh;
	RECT			Rect, rcSource;
	float			PixelsX, PixelsY, MMX, MMY;

	// Get a reference DC. Normally, you'd get the highest resolution DC available,
	//    for example a printer DC. We just use a screen DC for this demonstration.
	if( (hRefDC = GetDC( NULL )) == NULL )
		return NULL;
	// Open the source EMF
	if( (hSourceEMF = GetEnhMetaFile( szSourceFileName )) == NULL )
	{
		ReleaseDC( NULL, hRefDC );
		return NULL;
	}

	// Get the header from the enhanced metafile.
	ZeroMemory( &emh, sizeof(ENHMETAHEADER) );
	emh.nSize = sizeof(ENHMETAHEADER);
	if( GetEnhMetaFileHeader( hSourceEMF, sizeof( ENHMETAHEADER ), &emh ) == 0 )
	{
		DeleteEnhMetaFile( hSourceEMF );
		ReleaseDC( NULL, hRefDC );
		return NULL;
	}

	// Get the characteristics of the output device.
	PixelsX = (float)GetDeviceCaps( hRefDC, HORZRES );
	PixelsY = (float)GetDeviceCaps( hRefDC, VERTRES );
	MMX = (float)GetDeviceCaps( hRefDC, HORZSIZE );
	MMY = (float)GetDeviceCaps( hRefDC, VERTSIZE );

	// Calculate the rect in which to draw the metafile based on the
	// intended size and the current output device resolution.
	// Remember that the intended size is given in 0.01 mm units, so
	// convert those to device units on the target device.
	Rect.top = (int)((float)(emh.rclFrame.top) * PixelsY / (MMY*100.0f));
	Rect.left = (int)((float)(emh.rclFrame.left) * PixelsX / (MMX*100.0f));
	Rect.right = (int)((float)(emh.rclFrame.right) * PixelsX / (MMX*100.0f));
	Rect.bottom = (int)((float)(emh.rclFrame.bottom) * PixelsY / (MMY*100.0f));

	// Create the new metafile the same size as the old one.
	SetRect( &rcSource, emh.rclFrame.left, emh.rclFrame.top, emh.rclFrame.right, emh.rclFrame.bottom );
	hTargetDC = CreateEnhMetaFile( hRefDC, szTargetFileName, &rcSource, "Desc\0Desc\0\0" );
	// Play the old metafile on to the new one.
	PlayEnhMetaFile( hTargetDC, hSourceEMF, &Rect );
	// Clean up.
	DeleteEnhMetaFile( hSourceEMF );
	ReleaseDC( NULL, hRefDC );
	return hTargetDC;
}