john@trigraph.UUCP (John Chew) (03/28/89)
Here's yet another offscreen bitmap question.
It all started out when I had to write a program that would
take AppleScan-generated files and convert them to some arbitrary
bitmap format for use in another environment. All I wanted was
the dimensions of the scanned image, and a stream of hex representing
the bitmap. The images were all to be 100 dpi and one bit deep.
I *could* have used TIFF files but I thought that PICT files would
be easier to decode, and besides, the people who wrote AppleScan
must have thought so since they didn't make any provision for reading
TIFF files back into AppleScan for touching up.
So the basic strategy was to read the MacDraw header to get the
resolution and bounding box, then spool the rest of the file (the
PICT2) into an offscreen pixmap and extract the data starting at
baseAddr.
The problem is that doing simply this results in a 72% scaled
bitmap, as CQD is clever enough to recognize that the pixmaps
in the PICT2 are 100 dpi and therefore need to be adjusted to
maintain the same dimensions on what is presumably a 72 dpi
offscreen pixmap.
I have not been able to think of a simple way of creating a
colour grafport with an offscreen pixmap that is one bit deep
regardless of the current screen depth, and whose resolution
is arbitrary and may not match the current screen. Can you?
[ I eventually patched the bitsProc bottleneck procedure to
fudge the arguments CopyBits() was being passed, but this
is just too ugly for words. ]
John
--
john j. chew, iii phone: +1 416 425 3818 AppleLink: CDA0329
trigraph, inc., toronto, canada {uunet!utai!utcsri,utgpu,utzoo}!trigraph!john
dept. of math., u. of toronto poslfit@{utorgpu.bitnet,gpu.utcs.utoronto.ca}