KoIntegerMaths.h

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/*
 *  SPDX-FileCopyrightText: 2005 Adrian Page <adrian@pagenet.plus.com>
 *
 * SPDX-License-Identifier: LGPL-2.0-or-later
*/
 
#ifndef KO_INTEGER_MATHS_H
#define KO_INTEGER_MATHS_H
 
#include <cstdint>
 
#ifndef UINT8_MAX
#define UINT8_MAX 255u
#endif
 
#ifndef UINT8_MIN
#define UINT8_MIN 0u
#endif
 
#ifndef UINT16_MAX
#define UINT16_MAX 65535u
#endif
 
#ifndef UINT16_MIN
#define UINT16_MIN 0u
#endif
 
#ifndef UINT32_MAX
#define UINT32_MAX (4294967295u)
#endif
 
#ifndef UINT32_MIN
#define UINT32_MIN 0u
#endif
 
#ifndef INT16_MAX
#define INT16_MAX 32767
#endif
 
#ifndef INT16_MIN
#define INT16_MIN -32768
#endif
 
typedef unsigned int uint;
 
template<typename _T_, typename _T2_, typename _T3_>
inline _T_ CLAMP(_T_ x, _T2_ l, _T3_ u)
{
    if (x < l)
        return _T_(l);
    else if (x > u)
        return _T_(u);
    return x;
}
 
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_MULT3(uint a, uint b, uint c)
{
  uint t = a * b * c + 0x7F5B;
  return ((t >> 7) + t) >> 16;
}
 
inline uint UINT8_BLEND(uint a, uint b, uint alpha)
{
    // However the formula is 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)) * alpha + 0x80u;
    c = ((c >> 8) + c) >> 8;
    return 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