Path: utzoo!attcan!uunet!amdahl!ames!pasteur!agate!bionet!csd4.milw.wisc.edu!dogie!yahnke@vms.macc.wisc.edu
From: yahnke@vms.macc.wisc.edu (Ross Yahnke, MACC)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Drawing Points Fast ??
Message-ID: <1297@dogie.edu>
Date: 10 Mar 89 14:44:23 GMT
Sender: news@dogie.edu
Organization: Lawrence Berkeley Laboratory, Berkeley
Lines: 30

In article <2068@helios.ee.lbl.gov>, osborn@ux1.lbl.gov (James R Osborn) writes...
>Would
> 
>BitSet(bytePtr, numBit)   and   BitClr(bytePtr, numBit)
> 
>be faster than using MoveTo(h, v) with Line(0, 0)?  I guess you would

Short of writing assembler, isn't the following even faster
than BitSet & BitClr?

  byte *bmOrg;  /* ptr to start of bitmap image */
  int  bmRB;    /* rowBytes of bitmap image */
  byte *bytePtr;


  /* equivalent to: BitClr(bmOrg + (bmRB * y), x); */
  bytePtr = bmOrg + (bmRB * y) + (x >> 3);
  *bytePtr &= ~(1 << (7 - (x & 7)));

  /* equivalent to: BitSet(bmOrg + (bmRB * y), x); */
  bytePtr = bmOrg + (bmRB * y) + (x >> 3);
  *bytePtr |= (1 << (7 - (x & 7)));

(all assuming offscreen bitmaps, your own range checking and copybits
 to onscreen window, of course)

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