imath.h

/*
	DDS GIMP plugin

	Copyright (C) 2004-2012 Shawn Kirst <skirst@gmail.com>,
   with parts (C) 2003 Arne Reuter <homepage@arnereuter.de> where specified.

	This program is free software; you can redistribute it and/or
	modify it under the terms of the GNU General Public
	License as published by the Free Software Foundation; either
	version 2 of the License, or (at your option) any later version.

	This program is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
	General Public License for more details.

	You should have received a copy of the GNU General Public License
	along with this program; see the file COPYING.  If not, write to
	the Free Software Foundation, 51 Franklin Street, Fifth Floor
	Boston, MA 02110-1301, USA.
*/

#ifndef IMATH_H
#define IMATH_H

#ifndef MIN
# ifdef __GNUC__
#  define MIN(a, b)  ({typeof(a) _a=(a); typeof(b) _b=(b); _a < _b ? _a : _b;})
# else
#  define MIN(a, b)  ((a) < (b) ? (a) : (b))
# endif
#endif

#ifndef MAX
# ifdef __GNUC__
#  define MAX(a, b)  ({typeof(a) _a=(a); typeof(b) _b=(b); _a > _b ? _a : _b;})
# else
#  define MAX(a, b)  ((a) > (b) ? (a) : (b))
# endif
#endif

#define IS_POW2(x)     (!((x) & ((x) - 1)))
#define IS_MUL4(x)     (((x) & 3) == 0)

/* round integer x up to next multiple of 4 */
#define RND_MUL4(x)    ((x) + (4 - ((x) & 3)))

static inline int mul8bit(int a, int b)
{
   int t = a * b + 128;
   return((t + (t >> 8)) >> 8);
}

static inline int blerp(int a, int b, int x)
{
   return(a + mul8bit(b - a, x));
}

static inline int icerp(int a, int b, int c, int d, int x)
{
   int p = (d - c) - (a - b);
   int q = (a - b) - p;
   int r = c - a;
   return((x * (x * (x * p + (q << 7)) + (r << 14)) + (b << 21)) >> 21);
}

#endif