Enum Algorithm 

#[non_exhaustive]
#[repr(u8)]
pub enum Algorithm {
    DeltaE76 = 0,
    Cie94 = 1,
    Ciede2000 = 2,
    Ciede2000Exact = 3,
}

Color-difference algorithm used to map an arbitrary RGB query to its nearest Color in the xkcd palette.

Each variant corresponds to one of the per-metric Color::nearest_to_* methods. The enum exists so callers can store the choice as a value and pass it to higher-level APIs like colorthief::extract_with without committing to a specific Color::nearest_to_* callsite.

Marked #[non_exhaustive] so adding a future variant (e.g. CMC, CIEDE2010) is a non-breaking change for downstream consumers.

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.

DeltaE76 = 0

Delta E 76 — squared Euclidean LAB distance. Fastest by a wide margin (~470 ns/query on Apple Silicon NEON, ~940 ns scalar). SIMD-dispatched on every supported arch with bit- identical parity. Recommended for search-vocabulary indexing where throughput matters more than borderline accuracy.

Cie94 = 1

CIE94 (Delta E 94, graphic-arts weighting) — middle ground between Delta E 76’s speed and CIEDE2000’s accuracy. Uses only sqrt for transcendentals, so it vectorises cleanly. ~900 ns NEON / ~4.4 µs scalar. Asymmetric: the palette entry is the reference, the query is the sample.

Ciede2000 = 2

CIEDE2000 — the modern perceptual gold-standard formula. With feature = "lut" (the default) routes through the candidate-set LUT (~230 ns/query, provably exact at u8 RGB); without the feature falls back to the full-scan reference (~71 µs/query, also provably exact). Behaviorally equivalent to Self::Ciede2000Exact under both feature configurations.

Ciede2000Exact = 3

CIEDE2000, retained as a distinct variant for API stability. Behaviorally equivalent to Self::Ciede2000 — both go through the LUT when feature = "lut" is enabled and the full-scan reference otherwise. Default. Returned by Algorithm::default so consumers of Algorithm::extract and crate-level entry points like colorthief::extract get the perceptual gold-standard out of the box.

Implementations

impl Algorithm

pub fn extract(&self, rgb: [u8; 3]) -> &'static Color

Find the Color whose pre-computed LAB is closest to the given RGB under this algorithm’s distance metric.

Equivalent to dispatching to the corresponding Color::nearest_to* method by hand:

Variant	Equivalent call
Self::DeltaE76	Color::nearest_to
Self::Cie94	Color::nearest_to_cie94
Self::Ciede2000	Color::nearest_to_ciede2000
Self::Ciede2000Exact	Color::nearest_to_ciede2000_exact

pub const fn as_str(&self) -> &'static str

Stable string identifier for this algorithm — useful for log lines, telemetry, and search-index metadata. Mirrors the Family::as_str / Kind::as_str convention.

Trait Implementations

impl Clone for Algorithm

fn clone(&self) -> Algorithm

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Algorithm

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

Formats the value using the given formatter.

impl Default for Algorithm

fn default() -> Algorithm

Returns the “default value” for a type.

impl Hash for Algorithm

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

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 Ord for Algorithm

fn cmp(&self, other: &Algorithm) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized,

Restrict a value to a certain interval.

impl PartialEq for Algorithm

fn eq(&self, other: &Algorithm) -> 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 PartialOrd for Algorithm

fn partial_cmp(&self, other: &Algorithm) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

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

Tests less than (for self and other) and is used by the < operator.

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

Tests less than or equal to (for self and other) and is used by the <= operator.

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

Tests greater than (for self and other) and is used by the > operator.

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

Tests greater than or equal to (for self and other) and is used by the >= operator.

impl Copy for Algorithm

impl Eq for Algorithm

impl StructuralPartialEq for Algorithm