QVision: Qt's Image, Video and Computer Vision Library

00001 /*
00002  *      Copyright (C) 2011, 2012. PARP Research Group.
00003  *      <http://perception.inf.um.es>
00004  *      University of Murcia, Spain.
00005  *
00006  *      This file is part of the QVision library.
00007  *
00008  *      QVision is free software: you can redistribute it and/or modify
00009  *      it under the terms of the GNU Lesser General Public License as
00010  *      published by the Free Software Foundation, version 3 of the License.
00011  *
00012  *      QVision is distributed in the hope that it will be useful,
00013  *      but WITHOUT ANY WARRANTY; without even the implied warranty of
00014  *      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00015  *      GNU Lesser General Public License for more details.
00016  *
00017  *      You should have received a copy of the GNU Lesser General Public
00018  *      License along with QVision. If not, see <http://www.gnu.org/licenses/>.
00019  */
00020 
00024 
00025 #include <qvmath.h>
00026 
00027 int qvIteratedBitCount(unsigned int n)
00028         {
00029         // Source for the code: http://gurmeet.net/puzzles/fast-bit-counting-routines/
00030         int count = 0;
00031         while (n)
00032                 {
00033                 count += n & 0x1u;
00034                 n >>= 1;
00035                 }
00036         return count;
00037         }
00038 
00039 int qvMITHAKMEMBitCount(unsigned int n)
00040         {
00041         // Source for the code: http://gurmeet.net/puzzles/fast-bit-counting-routines/
00042         /* works for 32-bit numbers only    */
00043         /* fix last line for 64-bit numbers */
00044         register unsigned int tmp;
00045         tmp = n - ((n >> 1) & 0xdb6db6db) - ((n >> 2) & 0x49249249);
00046         return ((tmp + (tmp >> 3)) & 0xc71c71c7) % 63;
00047         }
00048 
00049 int qvNiftyParallelBitCount(unsigned int n)
00050         {
00051         // Source for the code: http://gurmeet.net/puzzles/fast-bit-counting-routines/
00052         n = (n & 0x55555555) + ((n >> 1) & 0x55555555);
00053         n = (n & 0x33333333) + ((n >> 2) & 0x33333333);
00054         n = (n & 0x0f0f0f0f) + ((n >> 4) & 0x0f0f0f0f);
00055         return n % 255;
00056         }
00057
src/qvmath/qvbitcount.cpp
