Struct GainMapParams 

#[non_exhaustive]
pub struct GainMapParams {
    pub channels: [GainMapChannel; 3],
    pub base_hdr_headroom: f64,
    pub alternate_hdr_headroom: f64,
    pub use_base_color_space: bool,
    pub backward_direction: bool,
}

ISO 21496-1 gain map parameters. Canonical cross-codec representation.

Gains and headroom are in log2 domain. Gamma and offsets are in linear domain. This matches the ISO 21496-1 wire format directly, avoiding the domain confusion that occurs when converting between log2 and linear representations.

Fields (Non-exhaustive)

Non-exhaustive structs could have additional fields added in future. Therefore, non-exhaustive structs cannot be constructed in external crates using the traditional Struct { .. } syntax; cannot be matched against without a wildcard ..; and struct update syntax will not work.

channels: [GainMapChannel; 3]

Per-channel parameters. [0] = R (or all channels if single-channel), [1] = G, [2] = B.

base_hdr_headroom: f64

Log2 of base image HDR headroom. 0.0 = SDR (peak luminance ratio 1:1).

alternate_hdr_headroom: f64

Log2 of alternate image HDR headroom.

use_base_color_space: bool

Whether the gain map is encoded in the base image’s color space.

backward_direction: bool

ISO 21496-1 backward direction flag (bit 2 of flags byte).

When true, the base and alternate roles are reversed: the base image is the HDR rendition and the alternate is SDR. This is the authoritative encoder signal — direction() derives the same information from headroom comparison as a fallback.

Implementations

impl GainMapParams

pub fn is_single_channel(&self) -> bool

Whether all three channels have identical parameters.

pub fn direction(&self) -> GainMapDirection

Derive direction from headroom comparison.

The image with greater headroom is the HDR rendition.

pub fn linear_base_headroom(&self) -> f64

Base HDR headroom in linear domain: 2^base_hdr_headroom.

pub fn linear_alternate_headroom(&self) -> f64

Alternate HDR headroom in linear domain: 2^alternate_hdr_headroom.

pub fn validate(&self) -> Result<(), GainMapParseError>

Validate parameters for correctness.

Checks for NaN/infinity, positive gamma, and min ≤ max per channel.

Trait Implementations

impl Clone for GainMapParams

fn clone(&self) -> GainMapParams

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for GainMapParams

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

Formats the value using the given formatter.

impl Default for GainMapParams

fn default() -> Self

Returns the “default value” for a type.

impl PartialEq for GainMapParams

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