Path: utzoo!mnetor!uunet!kddlab!ccut!tansei!b39756
From: b39756@tansei.cc.u-tokyo.JUNET (Martin J. Duerst)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Polygon question
Message-ID: <1859@tansei.cc.u-tokyo.JUNET>
Date: 26 Apr 88 02:24:11 GMT
References: <24153@brunix.UUCP> <104700016@uiucdcsp>
Reply-To: b39756@tansei.cc.u-tokyo.JUNET (Martin J. Duerst)
Organization: Computer Center, University of Tokyo, Japan.
Lines: 24

Here is another method to count bits. Hope this helps:
Build up a table with 256 entries, one for each possible value
of a byte, containing the number of '1' bits for the
corresponding byte, like the following:

0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4, 1, etc.
(These are the values of the first few entries.)

This table has to be built up only once for the whole program.
For counting the bits, take each byte of your picture and look
up the corresponding value in the table. Adding up all the values
for all the bytes of your picture will give you the right result.
Smaller or larger tables (e.g. size 2**16) are also possible, but
may be use too much space or too much time to build up. 256 is
a very convenient size.
This should be quite fast if nicely implemented, but I didn't try
it myself.

Martin J. Duerst                       UUCP: See header.
Dept. of Information Science           BITNET: TU$KUNII@JPNSUT00
Faculty of Science                     (The '$' in the userid makes
University of Tokyo                     this unaccessible from many
7-3-1 Hongo, Bunkyo-ku                  sites.)
113 Tokyo, Japan