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.Dd December 21, 2022
.Dt AG_COLOR 3
.Os Agar 1.7
.Sh NAME
.Nm AG_Color
.Nd agar color structure
.Sh SYNOPSIS
.Bd -literal
#include <agar/core.h>
#include <agar/gui.h>
.Ed
.Sh DESCRIPTION
The
.Nm
structure describes a color in terms of
.Em Red ,
.Em Green ,
.Em Blue ,
and
.Em Alpha
components.
The
.Nm
structure is declared as:
.Bd -literal
.\" SYNTAX(c)
typedef struct ag_color {
#if AG_MODEL == AG_LARGE
	Uint16 r,g,b,a;			/* LG (16-bit color) */
#else
	Uint8  r,g,b,a;			/* MD (8-bit color) */
#endif
} AG_Color;
.Ed
.Pp
The alpha component may or may not be used in a given context.
A value of 0 (or
.Dv AG_TRANSPARENT
or
.Dv AG_COLOR_FIRST )
is fully transparent, while
.Dv AG_OPAQUE
(or
.Dv AG_COLOR_LAST )
is fully opaque.
.Sh INTERFACE
.nr nS 1
.Ft void
.Fn AG_ColorRGB_8 "AG_Color *c" "Uint8 r" "Uint8 g" "Uint8 b"
.Pp
.Ft void
.Fn AG_ColorRGBA_8 "AG_Color *c" "Uint8 r" "Uint8 g" "Uint8 b" "Uint8 a"
.Pp
.Ft void
.Fn AG_ColorRGB_16 "AG_Color *c" "Uint16 r" "Uint16 g" "Uint16 b"
.Pp
.Ft void
.Fn AG_ColorRGBA_16 "AG_Color *c" "Uint16 r" "Uint16 g" "Uint16 b" "Uint16 a"
.Pp
.Ft void
.Fn AG_HSV2Color "float hue" "float sat" "float val" "AG_Color *c"
.Pp
.Ft void
.Fn AG_Color2HSV "AG_Color *c" "float *hue" "float *sat" "float *val"
.Pp
.Ft void
.Fn AG_ColorHex16 "AG_Color *c" "Uint16 hex"
.Pp
.Ft void
.Fn AG_ColorHex32 "AG_Color *c" "Uint32 hex"
.Pp
.Ft void
.Fn AG_ColorHex64 "AG_Color *c" "Uint64 hex"
.Pp
.Ft void
.Fn AG_ColorFromString "AG_Color *c" "const char *spec" "const AG_Color *parentColor"
.Pp
.Ft void
.Fn AG_ColorNone "AG_Color *c"
.Pp
.Ft void
.Fn AG_ColorBlack "AG_Color *c"
.Pp
.Ft void
.Fn AG_ColorWhite "AG_Color *c"
.Pp
.Ft void
.Fn AG_ColorLighten "AG_Color *c" "int shade"
.Pp
.Ft void
.Fn AG_ColorDarken "AG_Color *c" "int shade"
.Pp
.Ft void
.Fn AG_ColorInterpolate "AG_Color *cx" "const AG_Color *c1" "const AG_Color *c2"
.Pp
.Ft int
.Fn AG_ColorCompare "const AG_Color *a" "const AG_Color *b"
.Pp
.nr nS 0
.Fn AG_ColorRGB_8
and
.Fn AG_ColorRGB_16
return an
.Ft AG_Color
from 8- or 16-bit red, green and blue components
(with alpha set to fully opaque).
.Pp
.Fn AG_ColorRGBA_8
and
.Fn AG_ColorRGBA_16
return an
.Ft AG_Color
from 8- or 16-bit RGB and alpha components.
.Pp
.Fn AG_HSV2Color
maps a color in HSV space to the closest approximation in RGB space, and
copies the A component as-is.
The inverse operation is performed by
.Fn AG_Color2HSV .
Note: H and V become increasingly lossy as S->0.
.Pp
The
.Fn AG_ColorHex16 ,
.Fn AG_ColorHex32
and
.Fn AG_ColorHex64
routines convert a color packed into
.Em 0xRGBA
(4-bit components),
.Em 0xRRGGBBAA
(8-bit components), or
.Em 0xRRRRGGGGBBBBAAAA
(16-bit components) into an
.Nm .
.Pp
.Fn AG_ColorFromString
converts a text-based color representation to an
.Nm .
The following formats are allowed:
.Bd -literal
"#RGB[A]"
"#RRGGBB[AA]"
"#RRRRGGGGBBBB[AAAA]"
"r,g,b[,a]"
"rgb(r,g,b[,a])"
"rgb16(r,g,b[,a])"
"hsv(h,s,v[,a])"
"AliceBlue"
.Ed
.Pp
Color components may be separated by `/', ':' or ','.
.Pp
A component terminating with a `%' character is interpreted as a ratio
(in %) of the corresponding component of
.Fa pColor
(or White if
.Fa pColor
is NULL).
.Pp
.Fn AG_ColorNone
initializes the color to fully transparent black (0,0,0,0).
.Fn AG_ColorBlack
and
.Fn AG_ColorWhite
initialize the respective fully opaque color.
.Pp
.Fn AG_ColorLighten
and
.Fa AG_ColorDarken
increase and decrease the overall value of
.Fa c
by some small increment multiplied by
.Fa shade .
A
.Fa shade
argument of 0 leaves the color value unchanged.
.Pp
.Fn AG_ColorInterpolate
traces an imaginary line in RGB color space between
.Fa c1
and
.Fa c2
and returns into
.Fa cx
the color closest to the point described by the fraction
.Fa num
over
.Fa denom .
.Pp
.Fn AG_ColorCompare
returns non-zero if the two colors differ.
.Sh SEE ALSO
.Xr AG_Intro 3 ,
.Xr AG_MapColorRGB 3 ,
.Xr AG_MapColorRGBA 3 ,
.Xr AG_MapPixelRGB 3 ,
.Xr AG_MapPixelRGBA 3 ,
.Xr AG_Surface 3 ,
.Xr AG_Widget 3
.Sh HISTORY
Agar 1.0 through 1.3 described colors using packed pixels in a 32-bit reference
format.
The
.Nm
structure first appeared in Agar 1.4.0.
Agar 1.6.0 introduced the
.Dv AG_LARGE
memory model and 48-bit "Deep Color".
.Fn AG_Color2HSV ,
.Fn AG_HSV2Color ,
.Fn AG_ColorNone ,
.Fn AG_ColorDarken ,
.Fn AG_ColorLighten
and the
.Fn AG_ColorInterpolate
functions appeared in 1.6.0.