Enum Quantize 

#[non_exhaustive]
pub enum Quantize {
    Perceptual,
    Euclidean,
}

The distance metric Color::to_indexed_with and Color::to_ansi_with use to find a palette entry’s nearest neighbour.

Examples

use retroglyph_core::color::{Color, Quantize};

let salmon = Color::rgb(250, 128, 114);
assert_eq!(salmon.to_indexed_with(Quantize::Perceptual), Color::Indexed(210));
assert_eq!(salmon.to_indexed_with(Quantize::Euclidean), Color::Indexed(209));

Variants (Non-exhaustive)

Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.

Perceptual

Euclidean distance in the Oklab perceptually-uniform color space.

Matches human color perception far better than raw RGB distance, at the cost of converting the input color to Oklab (three powf and three cbrt) on every call. The palette side of the comparison is precomputed, so that conversion is the whole cost.

The default, and what Color::to_indexed and Color::to_ansi use.

Euclidean

Euclidean distance over the raw 8-bit RGB channels.

Integer-only and allocation-free, and for Color::to_indexed_with it finds the 6x6x6 cube’s nearest point by rounding each channel independently rather than scanning the cube. Perceptually worse than Perceptual (it over-weights green and under-weights blue), but it’s the rule most terminal tooling applies, so it’s the one to pick when the output has to agree with another tool’s downgrade.

Trait Implementations

impl Clone for Quantize

fn clone(&self) -> Quantize

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for Quantize

impl Debug for Quantize

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl Default for Quantize

fn default() -> Quantize

Returns the “default value” for a type.

impl Eq for Quantize

impl Hash for Quantize

fn hash<__H>(&self, state: &mut __H)

where __H: Hasher,

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl PartialEq for Quantize

fn eq(&self, other: &Quantize) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl StructuralPartialEq for Quantize