KoIntegerMaths.h File Reference

#include <cstdint>

Go to the source code of this file.

Macros
#define	INT16_MAX   32767
#define	INT16_MIN   -32768
#define	UINT16_MAX   65535u
#define	UINT16_MIN   0u
#define	UINT32_MAX   (4294967295u)
#define	UINT32_MIN   0u
#define	UINT8_MAX   255u
#define	UINT8_MIN   0u

Typedefs
typedef unsigned int	uint

Functions
template<typename _T_ , typename _T2_ , typename _T3_ >
_T_	CLAMP (_T_ x, _T2_ l, _T3_ u)
int	INT16_BLEND (int a, int b, uint alpha)
int	INT16_MULT (int a, int b)
uint	UINT16_BLEND (uint a, uint b, uint alpha)
uint	UINT16_DIVIDE (uint a, uint b)
uint	UINT16_MULT (uint a, uint b)
uint	UINT16_TO_UINT8 (uint c)
uint	UINT8_BLEND (uint a, uint b, uint alpha)
uint	UINT8_DIVIDE (uint a, uint b)
uint	UINT8_MULT (uint a, uint b)
uint	UINT8_MULT3 (uint a, uint b, uint c)
	Approximation of (a * b * c + 32512) / 65025.0.
uint	UINT8_SCALEBY (uint a, uint b)
	take a and scale it up by 256*b/255
uint	UINT8_TO_UINT16 (uint c)

Macro Definition Documentation

INT16_MAX

#define INT16_MAX   32767

Definition at line 37 of file KoIntegerMaths.h.

INT16_MIN

#define INT16_MIN   -32768

Definition at line 41 of file KoIntegerMaths.h.

UINT16_MAX

#define UINT16_MAX   65535u

Definition at line 21 of file KoIntegerMaths.h.

UINT16_MIN

#define UINT16_MIN   0u

Definition at line 25 of file KoIntegerMaths.h.

UINT32_MAX

#define UINT32_MAX   (4294967295u)

Definition at line 29 of file KoIntegerMaths.h.

UINT32_MIN

#define UINT32_MIN   0u

Definition at line 33 of file KoIntegerMaths.h.

UINT8_MAX

#define UINT8_MAX   255u

Definition at line 13 of file KoIntegerMaths.h.

UINT8_MIN

#define UINT8_MIN   0u

Definition at line 17 of file KoIntegerMaths.h.

Typedef Documentation

uint

typedef unsigned int uint

Definition at line 44 of file KoIntegerMaths.h.

Function Documentation

CLAMP()

template<typename _T_ , typename _T2_ , typename _T3_ >

_T_ CLAMP ( _T_ x, _T2_ l, _T3_ u )

inline

Definition at line 47 of file KoIntegerMaths.h.

{
    if (x < l)
        return _T_(l);
    else if (x > u)
        return _T_(u);
    return x;
}

References u.

INT16_BLEND()

int INT16_BLEND ( int a, int b, uint alpha )

inline

Definition at line 136 of file KoIntegerMaths.h.

{
    // 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;
}

INT16_MULT()

int INT16_MULT ( int a, int b )

inline

Definition at line 103 of file KoIntegerMaths.h.

{
    return (a*b) / INT16_MAX;
}

References INT16_MAX.

UINT16_BLEND()

uint UINT16_BLEND ( uint a, uint b, uint alpha )

inline

Definition at line 114 of file KoIntegerMaths.h.

{
    // 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);
}

UINT16_DIVIDE()

uint UINT16_DIVIDE ( uint a, uint b )

inline

Definition at line 108 of file KoIntegerMaths.h.

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

References UINT16_MAX.

UINT16_MULT()

uint UINT16_MULT ( uint a, uint b )

inline

Definition at line 97 of file KoIntegerMaths.h.

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

UINT16_TO_UINT8()

uint UINT16_TO_UINT8 ( uint c )

inline

Definition at line 128 of file KoIntegerMaths.h.

{
    //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;
}

UINT8_BLEND()

uint UINT8_BLEND ( uint a, uint b, uint alpha )

inline

Blending of two scale values as described by the alpha scale value A scale value is interpreted as 255 equaling 1.0 (such as seen in rgb8 triplets) Basically we do: a*alpha + b*(1-alpha)

Definition at line 88 of file KoIntegerMaths.h.

{
    // 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;
}

UINT8_DIVIDE()

uint UINT8_DIVIDE ( uint a, uint b )

inline

Definition at line 72 of file KoIntegerMaths.h.

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

References UINT8_MAX.

UINT8_MULT()

uint UINT8_MULT ( uint a, uint b )

inline

multiplication of two scale values A scale value is interpreted as 255 equaling 1.0 (such as seen in rgb8 triplets) thus "255*255=255" because 1.0*1.0=1.0

Definition at line 66 of file KoIntegerMaths.h.

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

UINT8_MULT3()

uint UINT8_MULT3 ( uint a, uint b, uint c )

inline

Approximation of (a * b * c + 32512) / 65025.0.

Definition at line 79 of file KoIntegerMaths.h.

{
  uint t = a * b * c + 0x7F5B;
  return ((t >> 7) + t) >> 16;
}

UINT8_SCALEBY()

uint UINT8_SCALEBY ( uint a, uint b )

inline

take a and scale it up by 256*b/255

Definition at line 57 of file KoIntegerMaths.h.

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

UINT8_TO_UINT16()

uint UINT8_TO_UINT16 ( uint c )

inline

Definition at line 123 of file KoIntegerMaths.h.

{
    return c | (c << 8);
}