Detailed Description

Fast, efficient 8-bit scaling functions specifically designed for high-performance LED programming.

Because of the AVR(Arduino) and ARM assembly language implementations provided, using these functions often results in smaller and faster code than the equivalent program using plain "C" arithmetic and logic.

Modules
	Scaling Functions that Leave R1 Dirty
	These functions are more efficient for scaling multiple bytes at once, but require calling cleanup_R1() afterwards.

Functions
LIB8STATIC_ALWAYS_INLINE uint8_t	scale8 (uint8_t i, fract8 scale)
	Scale one byte by a second one, which is treated as the numerator of a fraction whose denominator is 256.

LIB8STATIC_ALWAYS_INLINE uint8_t	scale8_video (uint8_t i, fract8 scale)
	The "video" version of scale8() guarantees that the output will be only be zero if one or both of the inputs are zero.

LIB8STATIC void	nscale8x3 (uint8_t &r, uint8_t &g, uint8_t &b, fract8 scale)
	Scale three one-byte values by a fourth one, which is treated as the numerator of a fraction whose demominator is 256.

LIB8STATIC void	nscale8x3_video (uint8_t &r, uint8_t &g, uint8_t &b, fract8 scale)
	Scale three one-byte values by a fourth one, which is treated as the numerator of a fraction whose demominator is 256.

LIB8STATIC void	nscale8x2 (uint8_t &i, uint8_t &j, fract8 scale)
	Scale two one-byte values by a third one, which is treated as the numerator of a fraction whose demominator is 256.

LIB8STATIC void	nscale8x2_video (uint8_t &i, uint8_t &j, fract8 scale)
	Scale two one-byte values by a third one, which is treated as the numerator of a fraction whose demominator is 256.

LIB8STATIC_ALWAYS_INLINE uint16_t	scale16by8 (uint16_t i, fract8 scale)
	Scale a 16-bit unsigned value by an 8-bit value, which is treated as the numerator of a fraction whose denominator is 256.

LIB8STATIC uint16_t	scale16 (uint16_t i, fract16 scale)
	Scale a 16-bit unsigned value by an 16-bit value, which is treated as the numerator of a fraction whose denominator is 65536.

Function Documentation

◆ nscale8x2()

LIB8STATIC void nscale8x2	(	uint8_t &	i,
		uint8_t &	j,
		fract8	scale
	)

Scale two one-byte values by a third one, which is treated as the numerator of a fraction whose demominator is 256.

In other words, it computes i,j * (scale / 256).

Warning: This function always modifies its arguments in place!

Parameters

i	first value to scale
j	second value to scale
scale	scale factor, in n/256 units

Definition at line 418 of file scale8.h.

◆ nscale8x2_video()

LIB8STATIC void nscale8x2_video	(	uint8_t &	i,
		uint8_t &	j,
		fract8	scale
	)

Scale two one-byte values by a third one, which is treated as the numerator of a fraction whose demominator is 256.

In other words, it computes i,j * (scale / 256), ensuring that non-zero values passed in remain non zero, no matter how low the scale argument.

Warning: This function always modifies its arguments in place!

Parameters

i	first value to scale
j	second value to scale
scale	scale factor, in n/256 units

Definition at line 449 of file scale8.h.

◆ nscale8x3()

LIB8STATIC void nscale8x3	(	uint8_t &	r,
		uint8_t &	g,
		uint8_t &	b,
		fract8	scale
	)

Scale three one-byte values by a fourth one, which is treated as the numerator of a fraction whose demominator is 256.

In other words, it computes r,g,b * (scale / 256)

Warning: This function always modifies its arguments in place!

Parameters

r	first value to scale
g	second value to scale
b	third value to scale
scale	scale factor, in n/256 units

Definition at line 357 of file scale8.h.

◆ nscale8x3_video()

LIB8STATIC void nscale8x3_video	(	uint8_t &	r,
		uint8_t &	g,
		uint8_t &	b,
		fract8	scale
	)

Scale three one-byte values by a fourth one, which is treated as the numerator of a fraction whose demominator is 256.

In other words, it computes r,g,b * (scale / 256), ensuring that non-zero values passed in remain non-zero, no matter how low the scale argument.

Warning: This function always modifies its arguments in place!

Parameters

r	first value to scale
g	second value to scale
b	third value to scale
scale	scale factor, in n/256 units

Definition at line 392 of file scale8.h.

◆ scale16()

LIB8STATIC uint16_t scale16	(	uint16_t	i,
		fract16	scale
	)

Scale a 16-bit unsigned value by an 16-bit value, which is treated as the numerator of a fraction whose denominator is 65536.

In other words, it computes i * (scale / 65536)

Parameters

i	input value to scale
scale	scale factor, in n/65536 units

Returns: scaled value

Examples: Pacifica.ino.

Definition at line 543 of file scale8.h.

◆ scale16by8()

LIB8STATIC_ALWAYS_INLINE uint16_t scale16by8	(	uint16_t	i,
		fract8	scale
	)

Scale a 16-bit unsigned value by an 8-bit value, which is treated as the numerator of a fraction whose denominator is 256.

In other words, it computes i * (scale / 256)

Parameters

i	input value to scale
scale	scale factor, in n/256 units

Returns: scaled value

Definition at line 472 of file scale8.h.

◆ scale8()

LIB8STATIC_ALWAYS_INLINE uint8_t scale8	(	uint8_t	i,
		fract8	scale
	)

Scale one byte by a second one, which is treated as the numerator of a fraction whose denominator is 256.

In other words, it computes i * (scale / 256)

Parameters

i	input value to scale
scale	scale factor, in n/256 units

Returns: scaled value

Note: Takes 4 clocks on AVR with MUL, 2 clocks on ARM

Examples: Fire2012WithPalette.ino, NoisePlusPalette.ino, Pacifica.ino, and XYMatrix.ino.

Definition at line 30 of file scale8.h.

◆ scale8_video()

LIB8STATIC_ALWAYS_INLINE uint8_t scale8_video	(	uint8_t	i,
		fract8	scale
	)

The "video" version of scale8() guarantees that the output will be only be zero if one or both of the inputs are zero.

If both inputs are non-zero, the output is guaranteed to be non-zero.
This makes for better "video"/LED dimming, at the cost of several additional cycles.

Parameters

i	input value to scale
scale	scale factor, in n/256 units

Returns: scaled value

See also: scale8()

Definition at line 112 of file scale8.h.

Detailed Description

Modules

Functions

Function Documentation

◆ nscale8x2()

◆ nscale8x2_video()

◆ nscale8x3()

◆ nscale8x3_video()

◆ scale16()

◆ scale16by8()

◆ scale8()

◆ scale8_video()