Enum TransferFunction 

#[non_exhaustive]
#[repr(u8)]
pub enum TransferFunction {
    Linear = 0,
    Srgb = 1,
    Bt709 = 2,
    Pq = 3,
    Gamma22 = 5,
    Hlg = 4,
    Unknown = 255,
}

Encoding transfer function (OETF).

Describes how scene-linear light was encoded into the pixel values. For still image codecs, this is unambiguous: “sRGB” means the IEC 61966-2-1 curve, “PQ” means SMPTE ST 2084, etc. Video pipelines that need to distinguish OETF from EOTF should use CICP codes directly.

Discriminant values are internal — use from_cicp() / to_cicp() for CICP mapping.

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.

Linear = 0

Linear light (gamma 1.0).

Srgb = 1

sRGB transfer curve (IEC 61966-2-1).

Bt709 = 2

BT.709 transfer curve.

Pq = 3

Perceptual Quantizer (SMPTE ST 2084, HDR10).

Gamma22 = 5

Pure power-law gamma 2.2. Used for Adobe RGB (1998).

The Adobe RGB 1998 encoding spec (§4.3.4.2) defines pure gamma 2.19921875 with no linear segment near black. About 85% of real-world Adobe RGB ICC profiles (Adobe CS4, Windows ClayRGB1998 / AdobeRGB1998, macOS AdobeRGB1998, Linux AdobeRGB1998/compatibleWithAdobeRGB1998, Nikon, etc.) encode the TRC as curv count=1 (pure gamma) or equivalent paraType funcType=0.

A minority of profiles (saucecontrol’s Compact-ICC AdobeCompat-v4, some lcms2-generated variants) encode paraType funcType=3 with a linear toe (slope c=1/32, break d=0.05568). Those profiles are deliberately NOT normalized to this variant — they fall through to full CMS so their exact encoded curve is honored. See scripts/icc-gen/src/main.rs for the identification policy.

Hlg = 4

Hybrid Log-Gamma (CICP 18, ARIB STD-B67). BT.2100 HDR.

Unknown = 255

Transfer function is not known.

Implementations

impl TransferFunction

pub const fn from_cicp(tc: u8) -> Option<TransferFunction>

Map CICP transfer_characteristics code to a TransferFunction.

pub const fn to_cicp(self) -> Option<u8>

Convert to the CICP transfer_characteristics code.

pub fn reference_white_nits(&self) -> f32

Reference white luminance in nits.

• SDR (sRGB, BT.709, Linear, Unknown): 1.0 (relative/scene-referred)
• PQ: 203.0 (ITU-R BT.2408 reference white)
• HLG: 1.0 (scene-referred)

Trait Implementations

impl Clone for TransferFunction

fn clone(&self) -> TransferFunction

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for TransferFunction

impl Debug for TransferFunction

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

Formats the value using the given formatter.

impl Display for TransferFunction

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

Formats the value using the given formatter.

impl Eq for TransferFunction

impl Hash for TransferFunction

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 TransferFunction

fn eq(&self, other: &TransferFunction) -> 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 TransferFunction

impl TransferFunctionExt for TransferFunction

fn linearize(&self, v: f32) -> f32

Scalar EOTF: encoded signal → linear light.

fn delinearize(&self, v: f32) -> f32

Scalar OETF: linear light → encoded signal.