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|
=encoding UTF-8
=head1 NAME
BH_Color - color manipulation utility
=head1 SYNTAX
#include <BH/Color.h>
cc prog.c -o prog -lbh
=head1 DESCRIPTION
The BH_Color module provides mechanism for color representation and translation
between different color spaces color spaces (RGB, HSL and HSV). Additionally,
this module provides mechanism for blending two colors.
=head1 NOTES
Internally, color is stored in four 16-bit integers.
When converting between RGB and HSV/HSL there is ~0.009% error. While this is
not an issue, if you are using 8-bit RGB value, this may become a problem for
the 16-bit RGB values (not every RGB value can be represented in unique HSV/HSL
value). If you need this kind of precision, then this module is not for you.
Almost all color blending modes work like in other software packages. The
exception is I<BH_COLOR_MODE_SOFT_LIGHT>. This library opted-in for the Pegtop's
version of the formula (which might yield different results). This might be an
issue if you are trying to implement standard complient SVG or PDF renderer.
The I<BH_COLOR_MODE_HUE>, I<BH_COLOR_MODE_SATURATION>, I<BH_COLOR_MODE_COLOR>
and I<BH_COLOR_MODE_LUMINOSITY> are implemented in HSL color space.
=head1 API CALLS
=head2 BH_ColorRGBA8
void BH_ColorRGBA8(const BH_Color *color,
uint8_t *r,
uint8_t *g,
uint8_t *b,
uint8_t *a);
Gets 8-bit RGBA representation of the I<color>.
Parameters I<r>, I<g>, I<b>, I<a> represent color components in RGB color space.
=head2 BH_ColorRGBA16
void BH_ColorRGBA16(const BH_Color *color,
uint16_t *r,
uint16_t *g,
uint16_t *b,
uint16_t *a);
Gets 16-bit RGBA representation of the I<color>.
Parameters I<r>, I<g>, I<b>, I<a> represent color components in RGB color space.
=head2 BH_ColorRGBAf
void BH_ColorRGBAf(const BH_Color *color,
float *r,
float *g,
float *b,
float *a);
Gets floating-point RGBA representation of the I<color>.
Parameters I<r>, I<g>, I<b>, I<a> represent color components in RGB color space.
=head2 BH_ColorSetRGBA8
void BH_ColorSetRGBA8(BH_Color *color,
uint8_t r,
uint8_t g,
uint8_t b,
uint8_t a);
Sets 8-bit I<r>, I<g>, I<b>, I<a> components of the color.
=head2 BH_ColorSetRGBA16
void BH_ColorSetRGBA16(BH_Color *color,
uint16_t r,
uint16_t g,
uint16_t b,
uint16_t a);
Sets 16-bit I<r>, I<g>, I<b>, I<a> components of the color.
=head2 BH_ColorSetRGBAf
void BH_ColorSetRGBAf(BH_Color *color,
float r,
float g,
float b,
float a);
Sets floating-point I<r>, I<g>, I<b>, I<a> components of the color.
=head2 BH_ColorHSVAf
void BH_ColorHSVAf(const BH_Color *color,
float *h,
float *s,
float *v,
float *a);
Gets floating-point HSV representation of the I<color>.
Parameters I<h>, I<s>, I<v>, I<a> represent color components in HSV color space.
=head2 BH_ColorSetHSVAf
void BH_ColorSetHSVAf(BH_Color *color,
float h,
float s,
float v,
float a);
Sets floating-point I<h>, I<s>, I<v>, I<a> components of the color.
=head2 BH_ColorHSLAf
void BH_ColorHSLAf(const BH_Color *color,
float *h,
float *s,
float *l,
float *a);
Gets floating-point HSL representation of the I<color>.
Parameters I<h>, I<s>, I<l>, I<a> represent color components in HSV color space.
=head2 BH_ColorSetHSLAf
void BH_ColorSetHSLAf(BH_Color *color,
float h,
float s,
float l,
float a);
Sets floating-point I<h>, I<s>, I<l>, I<a> components of the color.
=head2 BH_ColorToRGBA
void BH_ColorToRGBA(const BH_Color *color,
BH_Color *out);
Converts I<color> to RGB color space.
=head2 BH_ColorToHSVA
void BH_ColorToHSVA(const BH_Color *color,
BH_Color *out);
Converts I<color> to HSV color space.
=head2 BH_ColorToHSLA
void BH_ColorToHSLA(const BH_Color *color,
BH_Color *out);
Converts I<color> to HSL color space.
=head2 BH_ColorBlend
void BH_ColorBlend(const BH_Color *foreground,
const BH_Color *background,
int mode,
BH_Color *dest);
Blends I<foreground> and I<background> color, using specified blending I<mode>.
The following modes can be used:
=over
=item B<BH_COLOR_MODE_NORMAL>
r = f
=item B<BH_COLOR_MODE_MULTIPLY>
r = f * b
=item B<BH_COLOR_MODE_SCREEN>
r = 1 - (1 - f) * (1 - b)
=item B<BH_COLOR_MODE_OVERLAY>
r = HardLight(b, f)
=item B<BH_COLOR_MODE_DARKEN>
r = min(f, b)
=item B<BH_COLOR_MODE_LIGHTEN>
r = max(f, b)
=item B<BH_COLOR_MODE_COLOR_DODGE>
r = min(1, b / (1 - f))
=item B<BH_COLOR_MODE_COLOR_BURN>
r = 1 - min(1, (1 - b) / f)
=item B<BH_COLOR_MODE_LINEAR_DODGE>
r = f + b
=item B<BH_COLOR_MODE_LINEAR_BURN>
r = f + b - 1
=item B<BH_COLOR_MODE_HARD_LIGHT>
if (f < 0.5)
r = Multipy(2 * f, b)
else
r = Screen(2 * f - 1, b)
=item B<BH_COLOR_MODE_SOFT_LIGHT>
r = (1 - 2 * f) * b^2 + 2 * f * b
=item B<BH_COLOR_MODE_DIFFERENCE>
r = abs(f - b)
=item B<BH_COLOR_MODE_EXCLUSION>
r = f + b - (2 * f * b)
=item B<BH_COLOR_MODE_HUE>
r = HSL(H(f), S(b), L(b))
=item B<BH_COLOR_MODE_SATURATION>
r = HSL(H(b), S(f), L(b))
=item B<BH_COLOR_MODE_COLOR>
r = HSL(H(f), S(f), L(b))
=item B<BH_COLOR_MODE_LUMINOSITY>
r = HSL(H(b), S(b), L(f))
=back
=head1 STRUCTURES
=head2 BH_Color
typedef struct BH_Color
{
int type;
union
{
struct
{
uint16_t r;
uint16_t g;
uint16_t b;
uint16_t a;
} rgba;
struct
{
uint16_t h;
uint16_t s;
uint16_t v;
uint16_t a;
} hsva;
struct
{
uint16_t h;
uint16_t s;
uint16_t l;
uint16_t a;
} hsla;
} data;
} BH_Color;
=head1 SEE ALSO
L<BH>
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