gv_math.h File Reference

Arithmetic helper functions. More...

#include <assert.h>
#include <limits.h>
#include <stdbool.h>
#include <stddef.h>
#include <string.h>

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Enumerations
enum	{ BYTES_PER_PIXEL = 4 }
	byte length of data per pixel in image data buffers More...

Functions
static int	fcmp (double a, double b)
	comparator for doubles
static int	imax (int a, int b)
	maximum of two integers
static int	imin (int a, int b)
	minimum of two integers
static bool	is_exactly_equal (double a, double b)
	are two values precisely the same?
static bool	is_exactly_zero (double v)
	is a value precisely 0.0?
static int	scale_clamp (int original, double scale)
	scale up or down a non-negative integer, clamping to [0, INT_MAX]
static void	argb2rgba (size_t width, size_t height, unsigned char *data)

Enumeration Type Documentation

anonymous enum

anonymous enum

Enumerator
BYTES_PER_PIXEL

Definition at line 87 of file gv_math.h.

Function Documentation

argb2rgba()

static void argb2rgba ( size_t  width, size_t  height, unsigned char *  data  )

inlinestatic

in-place conversion of ARGB32 big endian to RGBA32 little endian

Image data originating from sources like Cairo comes in a 4-byte-per-pixel format ordered {blue, green, red, alpha}. Some output libraries/devices instead consume a 4-byte-per-pixel format ordered {red, green, blue, alpha}. This function converts the former to the latter.

It is confusing to refer to these formats as ARGB32 and RGBA32 when the first is big endian and the second is little endian, and thus the mappings of letters in the acronym to bytes in memory are opposites. Nevertheless that appears to be what is in common usage.

Parameters

width	Width of the image in pixels
height	Height of the image in pixels
data	[inout] Image data in ARGB32 format on entry and RGBA32 format on exit

Definition at line 105 of file gv_math.h.

References BYTES_PER_PIXEL, and NULL.

Referenced by kitty_format().

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fcmp()

static int fcmp ( double  a, double  b  )

inlinestatic

Definition at line 14 of file gv_math.h.

Referenced by countHorzCross(), and countVertCross().

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imax()

static int imax ( int  a, int  b  )

inlinestatic

Definition at line 25 of file gv_math.h.

Referenced by agerr_va().

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imin()

static int imin ( int  a, int  b  )

inlinestatic

Definition at line 28 of file gv_math.h.

Referenced by common_init_node(), dfs(), dfs(), make_map_internal(), node_distinct_coloring_internal2(), QuadTree_get_nearest(), QuadTree_get_nearest_internal(), and sfprint().

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is_exactly_equal()

static bool is_exactly_equal ( double  a, double  b  )

inlinestatic

This function should only be used when you know you want comparison with no tolerance, which is rare. Floating-point arithmetic accumulates imprecision, so equality comparisons should generally include a non-zero tolerance to account for this. In general, this function is only applicable for checking things like “is this variable unchanged since a previous assignment from a literal?”

Parameters

a	First operand to comparison
b	Second operand to comparison

Returns

True if the values are equal

Definition at line 44 of file gv_math.h.

Referenced by is_exactly_zero(), is_set(), pango_textlayout(), point_init(), poly_init(), rgb2hsv(), and routesplines_().

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is_exactly_zero()

static bool is_exactly_zero ( double  v )

inlinestatic

This function should only be used when you know you want comparison with no tolerance, which is rare. Floating-point arithmetic accumulates imprecision, so equality comparisons should generally include a non-zero tolerance to account for this. Valid double representations even include -0.0, for which this function will return false. In general, this function is only applicable for checking things like “is this variable unchanged since a previous assignment from the literal 0?” or “did this value we parsed from user input originate from the string "0.0"?”

Parameters

v	Value to check

Returns

True if the value is equal to exactly 0.0

Definition at line 63 of file gv_math.h.

References is_exactly_equal().

Referenced by dotneato_args_initialize(), emit_begin_node(), get_inputscale(), isBox(), isRect(), poly_init(), and poly_inside().

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scale_clamp()

static int scale_clamp ( int  original, double  scale  )

inlinestatic

Parameters

original	Value to scale
scale	Scale factor to apply

Returns

Clamped result

Definition at line 72 of file gv_math.h.

References scale().

Referenced by dot2_rank(), nsiter2(), and rank1().

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