View of /trunk/imath.h

    1 /*
    2    DDS GIMP plugin
    3 
    4    Copyright (C) 2004-2008 Shawn Kirst <skirst@insightbb.com>,
    5    with parts (C) 2003 Arne Reuter <homepage@arnereuter.de> where specified.
    6 
    7    This program is free software; you can redistribute it and/or
    8    modify it under the terms of the GNU General Public
    9    License as published by the Free Software Foundation; either
   10    version 2 of the License, or (at your option) any later version.
   11 
   12    This program is distributed in the hope that it will be useful,
   13    but WITHOUT ANY WARRANTY; without even the implied warranty of
   14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   15    General Public License for more details.
   16 
   17    You should have received a copy of the GNU General Public License
   18    along with this program; see the file COPYING.  If not, write to
   19    the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
   20    Boston, MA 02111-1307, USA.
   21 */
   22 
   23 #ifndef IMATH_H
   24 #define IMATH_H
   25 
   26 #ifndef MIN
   27 #define MIN(a, b)  ((a) < (b) ? (a) : (b))
   28 #endif
   29 #ifndef MAX
   30 #define MAX(a, b)  ((a) > (b) ? (a) : (b))
   31 #endif
   32 
   33 #define IS_POW2(x)     (!((x) & ((x) - 1)))
   34 #define IS_MUL4(x)     (((x) & 3) == 0)
   35 
   36 /* round integer x up to next multiple of 4 */
   37 #define RND_MUL4(x)    ((x) + (4 - ((x) & 3)))
   38 
   39 static inline int mul8bit(int a, int b)
   40 {
   41    int t = a * b + 128;
   42    return((t + (t >> 8)) >> 8);
   43 }
   44 
   45 static inline int blerp(int a, int b, int x)
   46 {
   47    return(a + mul8bit(b - a, x));
   48 }
   49 
   50 static inline int icerp(int a, int b, int c, int d, int x)
   51 {
   52    int p = (d - c) - (a - b);
   53    int q = (a - b) - p;
   54    int r = c - a;
   55    return((x * (x * (x * p + (q << 7)) + (r << 14)) + (b << 21)) >> 21);
   56 }
   57 
   58 #endif