ocio 0.2.2

A pure Rust port of OpenColorIO, the color management framework for visual effects and animation.
Documentation 
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//! Apple camera builtins (port of `AppleCameras.cpp`).

use crate::builtins::color_matrix_helpers::{
    build_conversion_matrix, AdaptationMethod, Primaries, ACES_AP0, REC2020,
};
use crate::builtins::op_helpers::{add_matrix, create_half_lut, TransformVec};
use crate::builtins::registry::BuiltinTransformRegistry;
use crate::types::TransformDirection::Forward as FWD;

/// Apple Wide Gamut primaries (from the Apple Log 2 white paper).
pub const APPLE_WIDE_GAMUT: Primaries = Primaries::new(
    (0.725, 0.301),
    (0.221, 0.814),
    (0.068, -0.076),
    (0.3127, 0.3290),
);

/// Apple Log to linear (a half-domain LUT, as OCIO builds it with
/// `OCIO_LUT_SUPPORT`).
pub(crate) fn apple_log_to_linear(ops: &mut TransformVec) {
    const R_0: f64 = -0.05641088;
    const R_T: f64 = 0.01;
    const C: f64 = 47.28711236;
    const BETA: f64 = 0.00964052;
    const GAMMA: f64 = 0.08550479;
    const DELTA: f64 = 0.69336945;

    let p_t = C * (R_T - R_0).powf(2.0);
    create_half_lut(ops, move |input| {
        if input >= p_t {
            (2.0f64.powf((input - DELTA) / GAMMA) - BETA) as f32
        } else if input >= 0.0 {
            ((input / C).sqrt() + R_0) as f32
        } else {
            R_0 as f32
        }
    });
}

/// Register the Apple camera builtins.
pub(crate) fn register_all(registry: &mut BuiltinTransformRegistry) {
    registry.add_builtin(
        "APPLE_LOG_to_ACES2065-1",
        "Convert Apple Log to ACES2065-1",
        |ops| {
            apple_log_to_linear(ops);
            let m = build_conversion_matrix(&REC2020, &ACES_AP0, AdaptationMethod::Bradford)?;
            add_matrix(ops, &m, FWD);
            Ok(())
        },
    );

    // Apple Log 2 uses the same transfer function as Apple Log, but with the
    // wider Apple Wide Gamut primaries rather than Rec.2020.
    registry.add_builtin(
        "APPLE_LOG-APPLEWG_to_ACES2065-1",
        "Convert Apple Log 2 Apple Wide Gamut to ACES2065-1",
        |ops| {
            apple_log_to_linear(ops);
            let m =
                build_conversion_matrix(&APPLE_WIDE_GAMUT, &ACES_AP0, AdaptationMethod::Bradford)?;
            add_matrix(ops, &m, FWD);
            Ok(())
        },
    );

    registry.add_builtin(
        "CURVE - APPLE_LOG_to_LINEAR",
        "Convert Apple Log to linear",
        |ops| {
            apple_log_to_linear(ops);
            Ok(())
        },
    );
}