ffcine-filters 0.4.0

Frame filters (denoise, grain, ...) as Vulkan compute kernels that fuse into GPU passes
Documentation 
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//! Timeline effects (`docs/timeline.md#effect-schemas`): `ffcine.fx.denoise/1` and
//! `ffcine.fx.grain/1`, from an effect's `metadata.ffcine` object.

use serde::Deserialize;
use serde_json::{Map, Value};

use crate::denoise::spatial_over;
use crate::{Denoise, Grain, Preset};

pub const DENOISE: &str = "ffcine.fx.denoise/1";
pub const GRAIN: &str = "ffcine.fx.grain/1";

/// `ffcine.fx.denoise/1`: `preset` (`night`, `snow`: the values the others override), `luma`,
/// `chroma` (spatial strengths, 8-bit code values), `low_light` (bigger spatial search), `protect`
/// (spatial point protection), `temporal: {radius, strength, chroma, protect}` (`null`: off).
#[derive(Debug, Default, Deserialize)]
#[serde(default)]
struct DenoiseV1 {
    preset: Option<Preset>,
    luma: Option<f32>,
    chroma: Option<f32>,
    low_light: bool,
    protect: Option<f32>,
    temporal: Option<Map<String, Value>>,
}

fn params<T: for<'de> Deserialize<'de>>(meta: &Map<String, Value>) -> Result<T, String> {
    let mut m = meta.clone();
    m.remove("schema");
    serde_json::from_value(Value::Object(m)).map_err(|e| e.to_string())
}

/// Reads `ffcine.fx.denoise/1` parameters (the effect's `metadata.ffcine`).
pub fn denoise(meta: &Map<String, Value>) -> Result<Denoise, String> {
    let v: DenoiseV1 = params(meta)?;
    let base = v.preset.map_or_else(Denoise::default, Preset::denoise);
    // Fields given override the preset's, one by one; an explicit `null` turns the pass off.
    let temporal = match (v.temporal, meta.contains_key("temporal"), base.temporal) {
        (None, true, _) | (None, false, None) => None,
        (None, false, Some(t)) => Some(t),
        (Some(over), _, t) => {
            let mut m = match t.map(serde_json::to_value) {
                Some(Ok(Value::Object(m))) => m,
                _ => Map::new(),
            };
            m.extend(over);
            Some(serde_json::from_value(Value::Object(m)).map_err(|e| e.to_string())?)
        }
    };
    let radius = v.low_light.then_some(3);
    let spatial = spatial_over(base.spatial, v.luma, v.chroma, radius, v.protect);
    Ok(Denoise { temporal, spatial }.clamped())
}

/// Reads `ffcine.fx.grain/1` parameters: `strength`, `size`, `chroma`; `profiles` is ignored
/// (see [`grain_for`]).
pub fn grain(meta: &Map<String, Value>) -> Result<Grain, String> {
    grain_for(meta, None)
}

/// `ffcine.fx.grain/1` for a render profile: `profiles.<profile>` (`preview`, `master`, ...)
/// overrides the top-level fields.
pub fn grain_for(meta: &Map<String, Value>, profile: Option<&str>) -> Result<Grain, String> {
    let mut m = meta.clone();
    let profiles = m.shift_remove("profiles");
    if let Some(Value::Object(over)) = profile.and_then(|p| profiles.as_ref()?.get(p)) {
        m.extend(over.clone());
    }
    params(&m)
}

#[cfg(test)]
mod tests {
    use super::*;

    fn obj(s: &str) -> Map<String, Value> {
        serde_json::from_str(s).unwrap()
    }

    #[test]
    fn denoise_v1() {
        let d = denoise(&obj(
            r#"{"schema": "ffcine.fx.denoise/1", "luma": 2, "low_light": true,
                "temporal": {"radius": 3, "strength": 5}}"#,
        ))
        .unwrap();
        let s = d.spatial.unwrap();
        assert_eq!((s.radius, s.luma, s.chroma), (3, 2.0, 3.0));
        assert_eq!(d.temporal.unwrap().radius, 3);
        assert!(denoise(&obj(r#"{"temporal": {"radius": 2, "bogus": 1}}"#)).is_err());
    }

    #[test]
    fn denoise_preset_with_overrides() {
        let night = Preset::Night.denoise();
        assert_eq!(denoise(&obj(r#"{"preset": "night"}"#)).unwrap(), night);
        // One temporal field replaces that field only.
        let d = denoise(&obj(
            r#"{"preset": "night", "temporal": {"radius": 2}, "luma": 1}"#,
        ))
        .unwrap();
        let (t, want) = (d.temporal.unwrap(), night.temporal.unwrap());
        assert_eq!(t.radius, 2);
        assert_eq!((t.strength, t.protect), (want.strength, want.protect));
        let s = d.spatial.unwrap();
        assert_eq!((s.luma, s.chroma), (1.0, night.spatial.unwrap().chroma));
        // Passes can be turned off.
        let d = denoise(&obj(r#"{"preset": "night", "temporal": null, "luma": 0}"#)).unwrap();
        assert!(d.is_off());
        assert!(denoise(&obj(r#"{"preset": "aurora"}"#)).is_err());
    }

    #[test]
    fn grain_v1() {
        let g = grain(&obj(r#"{"schema": "ffcine.fx.grain/1", "strength": 2}"#)).unwrap();
        assert!((g.strength - 2.0).abs() < f32::EPSILON);
        assert!((g.size - Grain::default().size).abs() < f32::EPSILON);
        let m = obj(r#"{"strength": 2, "chroma": 0.4,
                        "profiles": {"preview": {"strength": 1}, "master": {"strength": 1.5}}}"#);
        assert!((grain(&m).unwrap().strength - 2.0).abs() < f32::EPSILON);
        let g = grain_for(&m, Some("master")).unwrap();
        assert!((g.strength - 1.5).abs() < f32::EPSILON);
        assert!((g.chroma - 0.4).abs() < f32::EPSILON);
        assert!((grain_for(&m, Some("other")).unwrap().strength - 2.0).abs() < f32::EPSILON);
    }
}