koffice/chalk/sdk/kis_integer_maths.h

/*
 *  Copyright (c) 2005 Adrian Page <adrian@pagenet.plus.com>
 *
 *  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; if not, write to the Free Software
 *  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 */

#ifndef KIS_INTEGER_MATHS_H
#define KIS_INTEGER_MATHS_H

#include <config.h>
#if defined(HAVE_STDINT_H)
#include <stdint.h>
#endif

#if !defined(UINT8_MAX)
#define UINT8_MAX 255u
#endif
#if !defined(UINT8_MIN)
#define UINT8_MIN 0u
#endif

#if !defined(UINT16_MAX)
#define UINT16_MAX 65535u
#endif
#if !defined(UINT16_MIN)
#define UINT16_MIN 0u
#endif

#if !defined(UINT32_MAX)
#define UINT32_MAX (4294967295u)
#endif
#if !defined(UINT32_MIN)
#define UINT32_MIN 0u
#endif

#if !defined(INT16_MAX)
#define INT16_MAX 32767
#endif
#if !defined(INT16_MIN)
#define INT16_MIN -32768
#endif

/// take a and scale it up by 256*b/255
inline uint UINT8_SCALEBY(uint a, uint b)
{
    uint c = a * b + 0x80u;
    return (c >> 8) + c;
}

inline uint UINT8_MULT(uint a, uint b)
{
    uint c = a * b + 0x80u;
    return ((c >> 8) + c) >> 8;
}

inline uint UINT8_DIVIDE(uint a, uint b)
{
    uint c = (a * UINT8_MAX + (b / 2u)) / b;
    return c;
}

inline uint UINT8_BLEND(uint a, uint b, uint alpha)
{
    // Basically we do a*alpha + b*(1-alpha)
    // However refactored to (a-b)*alpha + b  since that saves a multiplication
    // Signed arithmetic is needed since a-b might be negative
    int c = ((int(a) - int(b)) * int(alpha)) >> 8;

    return uint(c + b);
}

inline uint UINT16_MULT(uint a, uint b)
{
    uint c = a * b + 0x8000u;
    return ((c >> 16) + c) >> 16;
}

inline int INT16_MULT(int a, int b)
{
    return (a*b) / INT16_MAX;
}

inline uint UINT16_DIVIDE(uint a, uint b)
{
    uint c = (a * UINT16_MAX + (b / 2u)) / b;
    return c;
}

inline uint UINT16_BLEND(uint a, uint b, uint alpha)
{
    // Basically we do a*alpha + b*(1-alpha)
    // However refactored to (a-b)*alpha + b  since that saves a multiplication
    // Signed arithmetic is needed since a-b might be negative
    int c = ((int(a) - int(b)) * int(alpha)) >> 16;
    return uint(c + b);
}

inline uint UINT8_TO_UINT16(uint c)
{
    return c | (c<<8);
}

inline uint UINT16_TO_UINT8(uint c)
{
    //return round(c / 257.0);
    //For all UINT16 this calculation is the same and a lot faster (off by c/65656 which for every c is 0)
    c = c - (c >> 8) + 128;
    return c >>8;
}

inline int INT16_BLEND(int a, int b, uint alpha)
{
    // Basically we do a*alpha + b*(1-alpha)
    // However refactored to (a-b)*alpha + b  since that saves a multiplication
    int c = ((int(a) - int(b)) * int(alpha)) >> 16;
    return c + b;
}

#endif