comms::Color Struct Reference

An 8-bit-per-channel RGBA color. Default is opaque black. More...

#include <color.hpp>

Public Member Functions
constexpr Color	fade (const f64 opacity_unit) const
	Set the alpha channel to the given [0, 1] opacity.
constexpr Color	opacity (const f64 opacity_unit) const
	Alias for fade — set the alpha channel to a [0, 1] opacity.
constexpr Color	lighten (const f64 amount) const
	Increase lightness by amount (unit delta, clamped).
constexpr Color	darken (const f64 amount) const
	Decrease lightness by amount (unit delta, clamped).
constexpr Color	saturate (const f64 amount) const
	Increase saturation by amount (unit delta, clamped).
constexpr Color	desaturate (const f64 amount) const
	Decrease saturation by amount (unit delta, clamped).
constexpr Color	rotate_hue (const f64 degrees) const
	Rotate the hue by degrees around the color wheel.
constexpr Color	recolor (const Color other) const
	Adopt the hue and saturation of other, keeping this color's lightness and alpha.
constexpr Color	tint (const f64 amount) const
	Alias for lighten.
constexpr Color	shade (const f64 amount) const
	Alias for darken.
constexpr Color	tone (const f64 amount) const
	Alias for desaturate.
constexpr Color	mix (const Color other, f64 t) const
	Linearly interpolate toward other by t (clamped to [0, 1]), including the alpha channel.
constexpr Color	blend_over (const Color bg) const
	Alpha-composite this color (source) over bg using the source-over operator.
constexpr Color	invert () const
	Invert the RGB channels, keeping alpha.
constexpr Color	grayscale () const
	Convert to gray using the Rec.601 luma weights (0.299 R, 0.587 G, 0.114 B), keeping alpha.
constexpr Color	complement () const
	The hue-opposite color (hue rotated 180°).
constexpr f64	relative_luminance () const
	Relative luminance per WCAG 2.x (sRGB linearized, then the 0.2126 / 0.7152 / 0.0722 weights).
constexpr f64	contrast_ratio (const Color other) const
	WCAG contrast ratio against other, in [1, 21]. Symmetric.
constexpr bool	is_light () const
	True when black text is at least as readable on this color as white.
constexpr Color	readable_text_color () const
	Black or white, whichever has the higher contrast against this color — the better foreground text color.
constexpr bool	has_readable_contrast (const Color text) const
	True when text over this background meets WCAG AA for normal text (contrast ratio >= 4.5).
constexpr std::array< Color, 2 >	split_complementary () const
	The two split-complementary colors (hue ±150°).
constexpr std::array< Color, 3 >	triadic () const
	This color plus the two triadic colors (hue +120°, +240°).
constexpr std::array< Color, 3 >	analogous (const f64 angle=30.0) const
	This color flanked by its two analogous neighbors (hue ∓angle).
std::string	to_hex_string () const
	Canonical hex: #RRGGBB when opaque, #RRGGBBAA otherwise.
std::string	to_css_rgb_string () const
	CSS space-separated form, e.g. "rgb(99 102 241)".
std::string	to_css_rgba_string () const
	CSS form with alpha, e.g.

Static Public Member Functions
static constexpr Color	from_rgb_int (const u32 v)
	0xRRGGBB (alpha forced opaque).
static constexpr Color	from_rgba_int (const u32 v)
	0xRRGGBBAA.
static constexpr Color	from_argb_int (const u32 v)
	0xAARRGGBB.
static constexpr std::optional< Color >	parse_hex (std::string_view s)
	Parse a hex color: #rgb, #rgba, #rrggbb, or #rrggbbaa (the leading # is optional).
static constexpr std::optional< Color >	parse (std::string_view s)
	Parse any supported textual color: hex (see parse_hex), CSS-functional rgb()/rgba()/hsl()/hsla(), or a CSS named color.

Public Attributes
u8	r = 0
	Red channel, [0, 255].
u8	g = 0
	Green channel, [0, 255].
u8	b = 0
	Blue channel, [0, 255].
u8	a = 255
	Alpha channel, [0, 255] (255 = opaque).

Detailed Description

An 8-bit-per-channel RGBA color. Default is opaque black.

Member Function Documentation

blend_over()

constexpr Color comms::Color::blend_over ( const Color  bg ) const

inlineconstexpr

Alpha-composite this color (source) over bg using the source-over operator.

The result's alpha is the combined coverage.

mix()

constexpr Color comms::Color::mix ( const Color  other, f64  t  ) const

inlineconstexpr

Linearly interpolate toward other by t (clamped to [0, 1]), including the alpha channel.

t == 0 is this color, t == 1 is other.

parse()

constexpr std::optional< Color > comms::Color::parse ( std::string_view  s )

staticconstexpr

Parse any supported textual color: hex (see parse_hex), CSS-functional rgb()/rgba()/hsl()/hsla(), or a CSS named color.

Returns nullopt if none match. Defined out-of-line below, once CssColors is complete.

parse_hex()

static constexpr std::optional< Color > comms::Color::parse_hex ( std::string_view  s )

inlinestaticconstexpr

Parse a hex color: #rgb, #rgba, #rrggbb, or #rrggbbaa (the leading # is optional).

Returns nullopt on any malformed input.

relative_luminance()

constexpr f64 comms::Color::relative_luminance ( ) const

inlineconstexpr

Relative luminance per WCAG 2.x (sRGB linearized, then the 0.2126 / 0.7152 / 0.0722 weights).

Alpha is ignored.

to_css_rgba_string()

std::string comms::Color::to_css_rgba_string ( ) const

inline

CSS form with alpha, e.g.

"rgb(99 102 241 / 1.0)" (alpha to one decimal place).

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The documentation for this struct was generated from the following file:

• include/commons/color.hpp