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From: rmh@apple.com (Rick Holzgrafe)
Newsgroups: comp.sys.mac,comp.sys.mac.programmer
Subject: Re: Mac II Palettes
Message-ID: <2773@internal.Apple.COM>
Date: 12 Jul 89 01:17:16 GMT
References: <635@sys.uea.ac.uk>
Sender: usenet@Apple.COM
Organization: Apple Computer, Inc.
Lines: 35

In article <635@sys.uea.ac.uk> swc@sys.uea.ac.uk (S.W. Cox CMP Staff) 
writes:
> The RGB colour entries in Mac II's palettes are supposed to be 0 - 65535
> but when converted to the conventional range 0 .. 1  by:
> 
>         newcol.red := col.red/65535  etc
> 
> where newcol.red, green and blue are reals, it starts inserting negative
> numbers (possibly -32767 to 32767 or something similar).
> 
> Can anybody think of a suitable assignment for going from the integers
> to the reals (and vice versa) apart from adding and subtracting 32767 
etc.
> 
>         Thanks, S Cox UEA Norwich, UK

Paraphrase from Inside Mac V-175 (The Color Picker Package):

RGBcolor fields are of type INTEGER, which is signed. There is another 
16-bit type called SmallFract of range 0..65535 which is assignment-
compatible with INTEGERs. There are two conversion routines:
    FUNCTION SmallFract2Fix(s: SmallFract): Fixed;
    FUNCTION Fix2SmallFract(f: Fixed): SmallFract;

So perhaps this will work for you:
    newcol.red := SmallFract2Fix(col.red);
where newcol.red is of type Fixed rather than Real. I haven't tried this, 
but I will soon because I have a similar problem.

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Rick Holzgrafe              |    {sun,voder,nsc,mtxinu,dual}!apple!rmh
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