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From: lsr@Apple.COM (Larry Rosenstein)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Offscreen BitMaps
Message-ID: <2910@internal.Apple.COM>
Date: 19 Jul 89 00:48:47 GMT
References: <3023@helios.ee.lbl.gov>
Sender: usenet@Apple.COM
Organization: Objects-R-Us,  Apple Computer, Inc.
Lines: 25

In article <3023@helios.ee.lbl.gov> osborn@ux1 (James R Osborn) writes:
> The code I am refering to is that which calculates the necessary
> rowbytes for your bitmap:

The March 1, 1988 version of Tech Note 41 does the calculation as:
       rowBytes := (((right - left) + 15) div 16) * 2;
with the equivalent translation to C.

>         rowBits = ourRect.right - ourRect.left;
>         numBytes = rowBits / 8;
> 
>         if (odd(numBytes))              /* You must write your own odd() 
*/
>                 numBytes += 1;
>         else if (rowBits % 8)           /* % is mod for pascal people */
>                 numBytes += 2;

What if rowBits ends up being 35?  Your code seems to result in numBytes 
== 4, when it should be 6.

Larry Rosenstein, Apple Computer, Inc.
Object Specialist

Internet: lsr@Apple.com   UUCP: {nsc, sun}!apple!lsr
AppleLink: Rosenstein1