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From: peters_r@mscf.med.upenn.edu
Newsgroups: comp.sys.mac.programmer
Subject: Converting Pichandles to bitmaps
Message-ID: <1991Jan24.020442.1@mscf.med.upenn.edu>
Date: 24 Jan 91 02:04:42 GMT
Sender: news@netnews.upenn.edu
Organization: University of Pennsylvania, Med School Computer Facility
Lines: 57


	Recently, I ran into problems with slow drawing during my drag and
Piupdate operations and decided to switch to copyBitting bitmaps instead of 
Drawpicturing pictures.  To my surprise, I could find no evidence of a Toolbox
routine to change pictures into bitmaps.  So here is one I wrote:

BitMap	*
PictureToBitMap( thePicture )
PicHandle	thePicture;
{
GrafPtr	tempPort = (GrafPtr) NewPtr(sizeof(GrafPort));
GrafPtr	savePort;
Rect	r;
int	theID;
BitMap	map;

GetPort( &savePort );

/* Create an off-screen grafport in which to draw the picture. */
OpenPort( tempPort );

/* Make sure that the structure, boundary, and size of the bitmap correspond
   to the picture we're going to draw. */
r = (**thePicture).picFrame;
map.bounds = r;
map.rowBytes = (((r.right - r.left) +15) /16) *2;
map.baseAddr = NewPtr( map.rowBytes * (r.bottom - r.top  +1));
SetPortBits( &map );

/* Make sure the port rectangle of our off-screen grafport is the same as the
   the picture frame. */
PortSize((r.right - r.left), (r.bottom - r.top));
SetPortBits( &map );

/* Drawing the picture will now alter our bitmap, and we'll capture the bit
   pattern we want. */
ClipRect( &tempPort->portRect );
EraseRect( &tempPort->portRect );
DrawPicture( thePicture, &r );

/* Clean up after ourselves. */
SetPort( savePort );
ClosePort( tempPort );
DisposPtr( tempPort );

/* Return home triumphant with the trophy. */
return &map;
}

Please let me know if this works for you ( it works fine on a mac plus running
system 6.0.5 (with old-style QuickDraw?)).  Also let me know if in your
references you find a  more up-to-date Toolbox function which does this. l am
also always on the lookout for ways to improve efficientcy.

Thanks,
Randy Peters