Rgba

An sRGB color with 8 bits per channel and an alpha (opacity) channel.

Rgb is always opaque; Rgba adds the alpha of #rrggbbaa and rgb(r g b / a). The alpha is a u8 like the other channels: 255 is opaque, 0 fully transparent. Display writes the #rrggbb form when opaque and #rrggbbaa otherwise.

Import

use helpers4::color::Rgba;

Cargo feature color (enabled by default). To compile only this module:

cargo add helpers4 --no-default-features --features color

or in Cargo.toml:

[dependencies]
helpers4 = { version = "0.0.9", default-features = false, features = ["color"] }

Definition

pub struct Rgba { /* private fields */ }

Examples

use helpers4::color::{Rgb, Rgba};

let glass = Rgba::parse("#ff880080")?;
assert_eq!((glass.r(), glass.g(), glass.b(), glass.a()), (255, 136, 0, 128));
assert_eq!(glass.to_css(), "rgb(255 136 0 / 0.502)");
assert_eq!(glass.to_rgb(), Rgb::new(255, 136, 0)); // drops the alpha
assert_eq!(Rgba::parse("rgb(255 136 0 / 50%)")?.a(), 128);

Methods

new

pub fn new(r: u8, g: u8, b: u8, a: u8) -> Self

Builds a color from its four channels.

Parameters

Parameter	Type	Description
r	u8	Red, 0..=255.
g	u8	Green, 0..=255.
b	u8	Blue, 0..=255.
a	u8	Alpha, 0 (transparent) to 255 (opaque).

Returns

Self — The color.

Examples

use helpers4::color::Rgba;

assert_eq!(Rgba::new(255, 0, 0, 255).to_hex(), "#ff0000");

from_rgb

pub fn from_rgb(rgb: Rgb, a: u8) -> Self

Adds an alpha to an opaque color.

Parameters

Parameter	Type	Description
rgb	Rgb	The color.
a	u8	Alpha, 0 (transparent) to 255 (opaque).

Returns

Self — The color with that alpha.

Examples

use helpers4::color::{Rgb, Rgba};

assert_eq!(Rgba::from_rgb(Rgb::new(1, 2, 3), 4), Rgba::new(1, 2, 3, 4));

parse

pub fn parse(text: &str) -> Result<Self, ParseColorError>

Parses a color written as #rgba, #rrggbbaa, rgb(r g b / a), rgb(r, g, b, a), rgba(...), or any form Rgb::parse reads (which is opaque).

The alpha of a function is a number (0.5) or a percentage (50%); like in CSS, a value outside 0..=1 is clamped. Surrounding whitespace is ignored, and so is case.

Parameters

Parameter	Type	Description
text	&str	The color to parse.

Returns

Result<Self, ParseColorError> — The color.

Errors

A ParseColorError for an empty text, a # color with a bad length or digit, a malformed or out-of-range function, or an unknown name.

Examples

use helpers4::color::Rgba;

assert_eq!(Rgba::parse("#f808")?, Rgba::new(255, 136, 0, 136));
assert_eq!(Rgba::parse("rgba(0, 0, 0, 0.5)")?, Rgba::new(0, 0, 0, 128));
assert_eq!(Rgba::parse("red")?, Rgba::new(255, 0, 0, 255));

r

pub fn r(self) -> u8

The red channel.

Returns

u8 — A value from 0 to 255.

g

pub fn g(self) -> u8

The green channel.

Returns

u8 — A value from 0 to 255.

b

pub fn b(self) -> u8

The blue channel.

Returns

u8 — A value from 0 to 255.

a

pub fn a(self) -> u8

The alpha channel.

Returns

u8 — A value from 0 (transparent) to 255 (opaque).

opacity

pub fn opacity(self) -> f64

The alpha as an opacity.

Returns

f64 — A value from 0.0 (transparent) to 1.0 (opaque).

Examples

use helpers4::color::Rgba;

assert_eq!(Rgba::new(0, 0, 0, 255).opacity(), 1.0);
assert_eq!(Rgba::new(0, 0, 0, 0).opacity(), 0.0);

to_rgb

pub fn to_rgb(self) -> Rgb

The same color without its alpha.

Returns

Rgb — The opaque Rgb.

Examples

use helpers4::color::{Rgb, Rgba};

assert_eq!(Rgba::new(1, 2, 3, 4).to_rgb(), Rgb::new(1, 2, 3));

to_hex

pub fn to_hex(self) -> String

The #rrggbb form when opaque, #rrggbbaa otherwise, in lower case.

Returns

String — For instance "#ff8800" or "#ff880080".

Examples

use helpers4::color::Rgba;

assert_eq!(Rgba::new(255, 136, 0, 128).to_hex(), "#ff880080");

to_css

pub fn to_css(self) -> String

The CSS form: rgb(r g b) when opaque, rgb(r g b / alpha) otherwise, with the alpha as an opacity rounded to 3 decimals.

Returns

String — For instance "rgb(255 136 0 / 0.502)".

Examples

use helpers4::color::Rgba;

assert_eq!(Rgba::new(255, 136, 0, 255).to_css(), "rgb(255 136 0)");
assert_eq!(Rgba::new(255, 136, 0, 0).to_css(), "rgb(255 136 0 / 0)");

Error type: ParseColorError

Why a string could not be parsed as a color.

use helpers4::color::ParseColorError;

#[non_exhaustive]
pub enum ParseColorError {
    /// The string is empty or only whitespace.
    Empty,
    /// A `#` color that does not have 3 or 6 hexadecimal digits.
    InvalidLength {
        /// The number of characters after the `#`.
        length: usize,
    },
    /// A character that is not a hexadecimal digit.
    InvalidDigit {
        /// Byte offset of the character in the input.
        index: usize,
    },
    /// An `rgb(...)` that does not hold exactly three whole numbers.
    InvalidFunction,
    /// A channel above 255 in `rgb(...)`.
    OutOfRange,
    /// Neither a `#hex` color, an `rgb(...)`, nor a known color name.
    UnknownName,
}

Source

src/color/rgba.rs