Release 0.13.4

The scene clicked 40px to the right of "pick", on "reset", so the
recording showed a neutral group being reset and a click on the wall
that panned. Re-recorded with the picker fixed: the word lights, the
sample moves temperature and tint, and Before shows what it corrected.

Cargo.lock

@@ -1221,7 +1221,7 @@ checksum = "f27ae1dd37df86211c42e150270f82743308803d90a6f6e6651cd730d5e1732f"
 
 [[package]]
 name = "darkroom-android"
-version = "0.13.3"
+version = "0.13.4"
 dependencies = [
  "android_logger",
  "dr-plat",
@@ -1234,7 +1234,7 @@ dependencies = [
 
 [[package]]
 name = "darkroom-desktop"
-version = "0.13.3"
+version = "0.13.4"
 dependencies = [
  "anyhow",
  "dr-plat",
@@ -1408,7 +1408,7 @@ checksum = "d8b14ccef22fc6f5a8f4d7d768562a182c04ce9a3b3157b91390b52ddfdf1a76"
 
 [[package]]
 name = "dr-bench"
-version = "0.13.3"
+version = "0.13.4"
 dependencies = [
  "anyhow",
  "dr-catalog",
@@ -1425,7 +1425,7 @@ dependencies = [
 
 [[package]]
 name = "dr-catalog"
-version = "0.13.3"
+version = "0.13.4"
 dependencies = [
  "dr-face",
  "dr-plat",
@@ -1440,7 +1440,7 @@ dependencies = [
 
 [[package]]
 name = "dr-decode"
-version = "0.13.3"
+version = "0.13.4"
 dependencies = [
  "dr-types",
  "env_logger",
@@ -1454,7 +1454,7 @@ dependencies = [
 
 [[package]]
 name = "dr-export"
-version = "0.13.3"
+version = "0.13.4"
 dependencies = [
  "dr-decode",
  "dr-gpu",
@@ -1473,7 +1473,7 @@ dependencies = [
 
 [[package]]
 name = "dr-face"
-version = "0.13.3"
+version = "0.13.4"
 dependencies = [
  "dr-inference-engine",
  "env_logger",
@@ -1486,7 +1486,7 @@ dependencies = [
 
 [[package]]
 name = "dr-film"
-version = "0.13.3"
+version = "0.13.4"
 dependencies = [
  "log",
  "serde",
@@ -1495,7 +1495,7 @@ dependencies = [
 
 [[package]]
 name = "dr-gpu"
-version = "0.13.3"
+version = "0.13.4"
 dependencies = [
  "bytemuck",
  "dr-decode",
@@ -1513,7 +1513,7 @@ dependencies = [
 
 [[package]]
 name = "dr-inference-engine"
-version = "0.13.3"
+version = "0.13.4"
 dependencies = [
  "libloading",
  "log",
@@ -1527,7 +1527,7 @@ dependencies = [
 
 [[package]]
 name = "dr-ingest"
-version = "0.13.3"
+version = "0.13.4"
 dependencies = [
  "dr-plat",
  "dr-types",
@@ -1539,7 +1539,7 @@ dependencies = [
 
 [[package]]
 name = "dr-lens"
-version = "0.13.3"
+version = "0.13.4"
 dependencies = [
  "lensfun",
  "log",
@@ -1547,7 +1547,7 @@ dependencies = [
 
 [[package]]
 name = "dr-pano"
-version = "0.13.3"
+version = "0.13.4"
 dependencies = [
  "dr-decode",
  "dr-inference-engine",
@@ -1561,7 +1561,7 @@ dependencies = [
 
 [[package]]
 name = "dr-pipeline"
-version = "0.13.3"
+version = "0.13.4"
 dependencies = [
  "dr-types",
  "log",
@@ -1570,7 +1570,7 @@ dependencies = [
 
 [[package]]
 name = "dr-plat"
-version = "0.13.3"
+version = "0.13.4"
 dependencies = [
  "android-native-keyring-store",
  "dr-types",
@@ -1586,7 +1586,7 @@ dependencies = [
 
 [[package]]
 name = "dr-preset-xmp"
-version = "0.13.3"
+version = "0.13.4"
 dependencies = [
  "dr-pipeline",
  "log",
@@ -1596,7 +1596,7 @@ dependencies = [
 
 [[package]]
 name = "dr-segment"
-version = "0.13.3"
+version = "0.13.4"
 dependencies = [
  "dr-inference-engine",
  "env_logger",
@@ -1609,7 +1609,7 @@ dependencies = [
 
 [[package]]
 name = "dr-sync"
-version = "0.13.3"
+version = "0.13.4"
 dependencies = [
  "async-trait",
  "dr-plat",
@@ -1623,7 +1623,7 @@ dependencies = [
 
 [[package]]
 name = "dr-sync-folder"
-version = "0.13.3"
+version = "0.13.4"
 dependencies = [
  "async-trait",
  "dr-sync",
@@ -1635,7 +1635,7 @@ dependencies = [
 
 [[package]]
 name = "dr-sync-nextcloud"
-version = "0.13.3"
+version = "0.13.4"
 dependencies = [
  "async-trait",
  "dr-decode",
@@ -1657,7 +1657,7 @@ dependencies = [
 
 [[package]]
 name = "dr-thumbs"
-version = "0.13.3"
+version = "0.13.4"
 dependencies = [
  "dr-types",
  "jpeg-encoder",
@@ -1669,7 +1669,7 @@ dependencies = [
 
 [[package]]
 name = "dr-types"
-version = "0.13.3"
+version = "0.13.4"
 dependencies = [
  "serde",
  "serde_json",
@@ -1678,7 +1678,7 @@ dependencies = [
 
 [[package]]
 name = "dr-ui"
-version = "0.13.3"
+version = "0.13.4"
 dependencies = [
  "anyhow",
  "async-trait",
@@ -1720,7 +1720,7 @@ dependencies = [
 
 [[package]]
 name = "dr-xmp"
-version = "0.13.3"
+version = "0.13.4"
 dependencies = [
  "dr-types",
  "log",
@@ -7021,7 +7021,7 @@ checksum = "8df9b6e13f2d32c91b9bd719c00d1958837bc7dec474d94952798cc8e69eeec3"
 
 [[package]]
 name = "traceability"
-version = "0.13.3"
+version = "0.13.4"
 dependencies = [
  "anyhow",
  "serde",

Cargo.toml

@@ -29,7 +29,7 @@ members = [
 ]
 
 [workspace.package]
-version = "0.13.3"
+version = "0.13.4"
 edition = "2021"
 rust-version = "1.92"
 license = "GPL-3.0-or-later"

README.md

@@ -76,7 +76,7 @@ controls, its place in the chain and its tests.
 
 ## Where it stands
 
-**0.13.3**, seventeen tagged releases in. 184 numbered requirements in
+**0.13.4**, eighteen tagged releases in. 184 numbered requirements in
 scope, 84% of them claimed by code and [traced to it](docs/traceability.md);
 the rest are written down rather than merely absent.
 

core/dr-face/src/lib.rs

@@ -50,6 +50,7 @@ pub mod eyes;
 pub mod landmarks;
 pub mod naming;
 pub mod neighbours;
+pub mod references;
 
 /// Smallest long edge a face crop may be sampled from.
 ///

core/dr-face/src/references.rs

@@ -0,0 +1,232 @@
+//! TRACES: FR-CULL-10 | NFR-P9
+//! Which of a person's faces stand for them in a grouping pass.
+//!
+//! # Why not all of them
+//!
+//! Every face the user has ruled on enters [`crate::cluster`] as an anchor,
+//! and the pass compares every face against every other
+//! ([`crate::neighbours`] is exhaustive by design). So a person with 750
+//! confirmed faces costs 750 comparisons against each of the library's other
+//! faces, and the cost of naming a library well grows with how well it is
+//! named: a fully confirmed library of 25,000 faces spends almost the whole
+//! scan re-comparing faces whose identity is already settled against each
+//! other.
+//!
+//! Most of those comparisons say nothing new. A person's confirmed faces are
+//! heavily redundant — thirty frames from one afternoon are one point of
+//! view, not thirty — and a new face that matches one of them matches the
+//! others too. What a new face needs to be measured against is the person's
+//! *range*: the angles, ages and lights they have been photographed in, each
+//! represented once.
+//!
+//! # The choice: the most diverse of the good ones
+//!
+//! Two rules, in order.
+//!
+//! **Good enough to vouch.** Only faces whose raw embedding was at least
+//! [`MIN_REFERENCE_QUALITY`] long are eligible — a stricter floor than the
+//! gallery's ([`crate::embedding::MIN_GALLERY_QUALITY`]), because a reference
+//! is asked to speak *for* a person rather than merely be admitted to the
+//! comparison. A face whose length was never recorded is admitted, as it is
+//! everywhere else: a rule that cannot be checked admits rather than excludes.
+//!
+//! **As far apart as possible.** From the eligible pool, up to
+//! [`MAX_REFERENCES`] faces are chosen to maximise the volume they span —
+//! the determinant of their Gram matrix — greedily: start from the longest
+//! vector, and at each step add the face with the largest component
+//! orthogonal to everything chosen so far. That is Gram–Schmidt with a
+//! pivot, and the product of the squared residuals it picks *is* the
+//! determinant, so the greedy step is the exact greedy on the objective.
+//! The effect is that a near-duplicate of a chosen face has almost no
+//! residual and is passed over, while the one profile shot among two
+//! hundred frontal frames is taken early.
+//!
+//! What is not chosen still belongs to the person. Those faces keep their
+//! confirmations and are not touched by the pass; they are simply not
+//! compared, which is the whole saving.
+
+/// The most faces that stand for one person.
+///
+/// A hundred is far more points of view than a person has. What it bounds
+/// is the cost: with every person at the cap, a scan against the named part
+/// of a library is `people × 100` comparisons per face rather than
+/// `confirmations`, and the two part company as soon as a library is used.
+pub const MAX_REFERENCES: usize = 100;
+
+/// The shortest raw embedding that may stand for a person.
+///
+/// One above the gallery floor: a reference vouches for someone, and the
+/// margin keeps the faces that only just cleared the gallery — the ones
+/// nearest the middle of the sphere — out of the set that speaks for a
+/// person.
+pub const MIN_REFERENCE_QUALITY: f32 = 15.0;
+
+/// Whether a face of this quality may stand for a person.
+///
+/// `None` is "never measured" and is admitted, as in
+/// [`crate::embedding::in_gallery`].
+pub fn eligible(quality: Option<f32>) -> bool {
+    quality.is_none_or(|q| q >= MIN_REFERENCE_QUALITY)
+}
+
+/// Choose which of one person's faces stand for them.
+///
+/// `embeddings` and `quality` are one entry per face, the embeddings unit
+/// length and all of one dimension. Returns the indices chosen, in the order
+/// chosen — the first is the longest eligible vector, and each after it is
+/// the one furthest from the span of those before. Every eligible face is
+/// returned when there are `max` or fewer of them, so a person under the
+/// cap loses nothing.
+///
+/// Deterministic: equal residuals break on the longer vector, then the lower
+/// index, so two devices holding the same faces choose the same references
+/// and group the same way (`cluster::clustering_is_deterministic`).
+pub fn select(embeddings: &[&[f32]], quality: &[Option<f32>], max: usize) -> Vec<usize> {
+    debug_assert_eq!(embeddings.len(), quality.len());
+    let mut pool: Vec<usize> = (0..embeddings.len())
+        .filter(|&i| eligible(quality[i]))
+        .collect();
+    if pool.len() <= max {
+        return pool;
+    }
+    // Longest first, so the seed is the pool's front and a tie on residual
+    // resolves to the earlier position. A missing reading ranks below any
+    // measured one for this purpose only: it is admitted, but a face that
+    // was measured and found long is the better seed.
+    pool.sort_by(|&a, &b| {
+        let qa = quality[a].unwrap_or(0.0);
+        let qb = quality[b].unwrap_or(0.0);
+        qb.total_cmp(&qa).then(a.cmp(&b))
+    });
+
+    // Residuals: what remains of each pool vector outside the span of the
+    // chosen ones. Copied, since they are rewritten in place.
+    let mut residual: Vec<Vec<f32>> = pool.iter().map(|&i| embeddings[i].to_vec()).collect();
+    let mut taken = vec![false; pool.len()];
+    let mut chosen = Vec::with_capacity(max);
+
+    while chosen.len() < max {
+        // The face with the most left outside the span. The seed is the
+        // pool's front by construction: every unit vector has the same
+        // residual before anything is chosen, up to rounding, and rounding
+        // is not a reason to prefer one. After that `> best` and not `>=`,
+        // so a genuine tie keeps the earlier (longer) candidate.
+        let mut pick = None;
+        let mut best = 0.0_f32;
+        if chosen.is_empty() {
+            pick = Some(0);
+            best = residual[0].iter().map(|x| x * x).sum();
+        } else {
+            for (k, r) in residual.iter().enumerate() {
+                if taken[k] {
+                    continue;
+                }
+                let n2: f32 = r.iter().map(|x| x * x).sum();
+                if n2 > best {
+                    best = n2;
+                    pick = Some(k);
+                }
+            }
+        }
+        // Nothing left outside the span: every remaining face is a
+        // combination of the chosen ones and adds no volume.
+        let Some(k) = pick.filter(|_| best > 1e-6) else {
+            break;
+        };
+        taken[k] = true;
+        chosen.push(pool[k]);
+
+        // Project the chosen direction out of every remaining residual.
+        let inv = best.sqrt().recip();
+        let q: Vec<f32> = residual[k].iter().map(|x| x * inv).collect();
+        for (j, r) in residual.iter_mut().enumerate() {
+            if taken[j] {
+                continue;
+            }
+            let d: f32 = r.iter().zip(&q).map(|(a, b)| a * b).sum();
+            for (x, y) in r.iter_mut().zip(&q) {
+                *x -= d * y;
+            }
+        }
+    }
+    chosen
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn unit(v: &[f32]) -> Vec<f32> {
+        let n = v.iter().map(|x| x * x).sum::<f32>().sqrt();
+        v.iter().map(|x| x / n).collect()
+    }
+
+    #[test]
+    fn a_person_under_the_cap_keeps_every_eligible_face() {
+        let e = [unit(&[1.0, 0.0]), unit(&[0.0, 1.0]), unit(&[1.0, 1.0])];
+        let refs: Vec<&[f32]> = e.iter().map(Vec::as_slice).collect();
+        let q = [Some(20.0), None, Some(16.0)];
+        assert_eq!(select(&refs, &q, 100), vec![0, 1, 2]);
+    }
+
+    #[test]
+    fn a_short_vector_never_stands_for_a_person() {
+        let e = [unit(&[1.0, 0.0]), unit(&[0.0, 1.0])];
+        let refs: Vec<&[f32]> = e.iter().map(Vec::as_slice).collect();
+        let q = [Some(20.0), Some(MIN_REFERENCE_QUALITY - 0.01)];
+        assert_eq!(select(&refs, &q, 100), vec![0]);
+    }
+
+    /// Two hundred frames from one afternoon and one profile shot: the
+    /// profile is the second choice, not the two-hundred-and-first.
+    #[test]
+    fn the_odd_one_out_is_chosen_before_any_duplicate() {
+        let mut e: Vec<Vec<f32>> = Vec::new();
+        let mut q = Vec::new();
+        for i in 0..200 {
+            // Near-duplicates of one direction, with a little noise.
+            let t = (i as f32) * 1e-3;
+            e.push(unit(&[1.0, t, t * 0.5]));
+            q.push(Some(20.0 + (i % 7) as f32));
+        }
+        e.push(unit(&[0.0, 0.0, 1.0]));
+        q.push(Some(16.0));
+        let refs: Vec<&[f32]> = e.iter().map(Vec::as_slice).collect();
+        let chosen = select(&refs, &q, 3);
+        assert_eq!(chosen.len(), 3);
+        assert_eq!(
+            chosen[1], 200,
+            "the profile shot was not second: {chosen:?}"
+        );
+        // Seeded on the longest vector.
+        assert_eq!(q[chosen[0]], Some(26.0));
+    }
+
+    /// Faces inside the span of the chosen ones add no volume and are not
+    /// taken to fill the cap.
+    #[test]
+    fn the_cap_is_not_filled_from_inside_the_span() {
+        let e = [
+            unit(&[1.0, 0.0]),
+            unit(&[0.0, 1.0]),
+            unit(&[1.0, 1.0]),
+            unit(&[2.0, -1.0]),
+        ];
+        let refs: Vec<&[f32]> = e.iter().map(Vec::as_slice).collect();
+        let q = [Some(20.0); 4];
+        assert_eq!(select(&refs, &q, 3).len(), 2);
+    }
+
+    #[test]
+    fn the_choice_is_deterministic() {
+        let e: Vec<Vec<f32>> = (0..50)
+            .map(|i| {
+                let a = (i as f32) * 0.37;
+                unit(&[a.cos(), a.sin(), (a * 3.0).sin(), 0.2])
+            })
+            .collect();
+        let refs: Vec<&[f32]> = e.iter().map(Vec::as_slice).collect();
+        let q = vec![Some(18.0); 50];
+        assert_eq!(select(&refs, &q, 5), select(&refs, &q, 5));
+    }
+}

core/dr-pipeline/src/graph.rs

@@ -857,6 +857,17 @@ impl EditGraph {
         crate::operation::compose_camera_linear(&self.warps, self.framing.baseline(), view)
     }
 
+    /// TRACES: FR-DEV-3
+    /// The camera-space tap under this edit's own framing — crop, view,
+    /// rotation and all — so a fraction of what is on the canvas is a
+    /// fraction of what this renders. Nothing else of the edit: no
+    /// operation, no mask, no repair. See
+    /// [`crate::operation::compose_camera_probe`] for why the white balance
+    /// picker reads from here and not from the display.
+    pub fn compose_camera_probe(&self) -> ComposedShader {
+        crate::operation::compose_camera_probe(&self.warps, &self.framing)
+    }
+
     /// TRACES: FR-DEV-19c
     /// [`Self::compose_for`], with one layer's mask drawn over the picture.
     ///

core/dr-pipeline/src/lib.rs

@@ -65,7 +65,8 @@ pub use history::{Edit, Entry as HistoryEntry, History, Step};
 pub use lens::{compose_warps, ComposedWarp, LensProfile, Tca, Warp};
 pub use operation::{
     compose, compose_with_framing, Affects, ComposedShader, Helper, Invalidation, Operation,
-    OutputMode, Uniform, BASE_CURVE_POINTS, BASE_CURVE_UNIFORM_OFFSET, RESERVED_UNIFORM_FIELDS,
+    OutputMode, Uniform, BASE_CURVE_POINTS, BASE_CURVE_UNIFORM_OFFSET, CLIP_ONSET,
+    RESERVED_UNIFORM_FIELDS,
 };
 pub use preset::{LibraryParseError, NameError, Preset, PresetLibrary, Scope};
 pub use sidecar::{Sidecar, Version};

core/dr-pipeline/src/neutral.rs

@@ -69,20 +69,26 @@ const ROUNDS: u32 = 3;
 
 /// Below this a channel carries no ratio worth balancing.
 ///
-/// A sample in the deep shadows, or one taken on a blown highlight where a
-/// channel has already clipped to nothing, has no white balance in it: the
-/// logarithms below would run away and the picker would slam a slider to its
-/// stop. Refusing is the honest answer, and the caller reports that the point
-/// was not usable rather than moving the photograph.
+/// A sample in the deep shadows has no white balance in it: the logarithms
+/// below would run away and the picker would slam a slider to its stop.
+/// Refusing is the honest answer, and the caller reports that the point was
+/// not usable rather than moving the photograph. The other end — a blown
+/// highlight, where every channel has stopped counting — is refused by the
+/// caller before the sample is taken, because only the caller can see the
+/// sensor value; see [`crate::operation::CLIP_ONSET`].
 const FLOOR: f32 = 1e-4;
 
 /// TRACES: FR-DEV-3
 /// Move the graph so that `sample` renders neutral.
 ///
-/// `sample` is linear RGB, as the operation's own gains multiply it — that is,
-/// measured with the sampling operation at its defaults. Returns whether the
-/// graph was moved: `false` where the chain offers no white point widget, or
-/// where the colour has no balance in it to correct.
+/// `sample` is the linear triple the operation's own gains multiply — camera
+/// RGB with the camera's as-shot balance on, *before* the body's base curve
+/// and matrix, and with the sampling operation at its defaults. Not the
+/// pixel on the screen: the matrix mixes the channels on the way there, so
+/// a colour read after it does not answer to these gains, and a solve over
+/// one lands somewhere no sample asked for. Returns whether the graph was
+/// moved: `false` where the chain offers no white point widget, or where the
+/// colour has no balance in it to correct.
 ///
 /// **Absolute, not relative.** The values written depend on the colour and not
 /// on where the sliders happened to be, so sampling the same wall twice lands

core/dr-pipeline/src/operation.rs

@@ -431,9 +431,11 @@ pub enum OutputMode {
     /// no operations, and the caller fills the reserved uniforms neutral —
     /// unit white balance, identity matrix, base curve off — so what is
     /// stored is the sensor's own numbers, demosaiced and undistorted. Only
-    /// [`compose_camera_linear`] produces it, and only
-    /// `AdjustPass::render_camera_linear` accepts it, so the neutral
-    /// uniforms cannot be forgotten by a caller that composed it by mistake.
+    /// [`compose_camera_probe`] produces it — for a merge through
+    /// [`compose_camera_linear`], and for the white balance picker under the
+    /// edit's own framing — and only `AdjustPass::render_camera_linear`
+    /// accepts it, so the neutral uniforms cannot be forgotten by a caller
+    /// that composed it by mistake.
     ///
     /// Thirty-two bits rather than sixteen because the composite is written
     /// back as a RAW at the sensor's scale (FR-MRG-3): a 14-bit sensor has
@@ -490,6 +492,19 @@ pub const BASE_CURVE_UNIFORM_OFFSET: usize = 16;
 /// selection in [`compose_full`].
 pub const BASE_CURVE_POINTS: usize = 5;
 
+/// Where the highlight desaturation begins: the fraction of the white level
+/// above which a photosite is treated as clipped.
+///
+/// A photosite this close to saturation has stopped counting, so its ratio
+/// to its neighbours is not a colour. The generated prologue fades a pixel
+/// above this toward a neutral of the same brightness before any operation
+/// runs, and the white balance probe refuses to sample one: a blown sky is
+/// sensor white, which the as-shot multipliers make magenta, and a solve
+/// over that slams tint to its stop. One number, so the two cannot drift
+/// apart — a probe that accepted what the shader had already desaturated
+/// would be balancing against a pixel the photographer cannot see.
+pub const CLIP_ONSET: f32 = 0.985;
+
 /// Where an operation's own uniforms begin in the generated block.
 ///
 /// The base fields, then framing's. Exported because `dr-gpu` writes the
@@ -614,9 +629,26 @@ pub fn compose_camera_linear(
     // upright too, and `view` is a fraction of the upright frame.
     framing.set_baseline(baseline);
     framing.set_view(view);
+    compose_camera_probe(warps, &framing)
+}
+
+/// TRACES: FR-DEV-3
+/// The same tap under a framing the caller chose: the white balance probe.
+///
+/// A neutral picked off the canvas has to be measured in the space the
+/// white balance gains multiply, and that is camera RGB — the operation
+/// runs before the body's matrix, and a probe read after the matrix would
+/// be solving the wrong equation on any body whose matrix mixes the
+/// channels, which is every body. It also has to be measured at the pixel
+/// the canvas is showing, which is why this takes the edit's own framing
+/// where a merge passes the file's orientation and a tile.
+pub fn compose_camera_probe(
+    warps: &[Box<dyn crate::lens::Warp>],
+    framing: &Framing,
+) -> ComposedShader {
     compose_inner(
         &[],
-        &framing,
+        framing,
         ColourSpace::Srgb,
         &MaskStack::new(),
         &crate::spot::SpotSet::new(),
@@ -668,7 +700,7 @@ fn compose_inner(
     // twice and be bound to a texture of the wrong format.
     //
     // `forced` is the one exception, and it is not a caller flag in the
-    // sense above: `compose_camera_linear` is the only function that passes
+    // sense above: `compose_camera_probe` is the only function that passes
     // it, with an empty operation list, and the mode it forces has its own
     // storage format and its own render entry on the GPU side.
     let output_mode = forced.unwrap_or(
@@ -997,6 +1029,9 @@ fn compose_inner(
         .to_string()
     };
 
+    // Formatted with Rust's `Display` so the shader reads the same threshold
+    // the probe checks against; see `CLIP_ONSET`.
+    let clip_onset = CLIP_ONSET;
     let source = format!(
         "// GENERATED — do not edit.
 //
@@ -1067,7 +1102,7 @@ fn main(@builtin(global_invocation_id) gid: vec3<u32>) {{
     // A photosite at its white level carries no colour information — every
     // channel simply stopped counting — so the balance below must not be
     // allowed to tint it.
-    let clipped = smoothstep(0.985, 1.0, max(c.r, max(c.g, c.b)));
+    let clipped = smoothstep({clip_onset}, 1.0, max(c.r, max(c.g, c.b)));
 
     c = c * u.as_shot_wb.rgb;
 

docs/faces.md

@@ -821,6 +821,16 @@ here, and it is the phone and tablet story that should decide whether it gets bu
   already has, the raw vector written over the old one and its id, box and identity untouched
   (`faces::record_updates`). No detector runs and no suggestion is lost — the cost is the
   original fetched once more, since the length exists only at the moment of embedding.
+- **A person is stood for by their references.** Every face the user has ruled on is an anchor,
+  and the scan is exhaustive, so a person with 750 confirmations would cost 750 comparisons
+  against every other face — and the cost of a library would grow with how well it was named.
+  Instead each person enters through at most `MAX_REFERENCES` (100) of their anchored faces,
+  chosen by `dr_face::references`: those whose raw embedding is at least `MIN_REFERENCE_QUALITY`
+  (15) long, and among them the set spanning the greatest volume — greedy max-determinant, the
+  longest vector first and then, at each step, the face with the largest component orthogonal to
+  the chosen so far. Thirty frames from one afternoon contribute one reference; the single profile
+  shot is taken early. The faces not chosen keep their confirmations and are not touched by the
+  pass; they are simply not compared.
 
 **The algorithm.** Constrained average-link agglomeration over the probability graph, merging while
 the average pairwise probability exceeds **0.9** and no cannot-link is violated. Average-link rather

packaging/PKGBUILD

@@ -4,7 +4,7 @@
 # makes `makepkg -si` in this directory install what you are actually working
 # on. Swap `source` for a tagged tarball when there is something to release.
 pkgname=darkroom
-pkgver=0.13.3
+pkgver=0.13.4
 # Back to 1 with the version: a new pkgver is a new archive name, so there is
 # nothing for makepkg to reuse and nothing for a release number to disambiguate.
 pkgrel=1

tools/manual/scenes.py

@@ -207,7 +207,7 @@ def develop_wb():
     group('colour')
     rec('develop-wb')
     pause(0.4)
-    dr.click(1542, 767); pause(0.8)                    # pick
+    dr.click(1487, 776); pause(0.8)                    # pick
     dr.click(1000, 300); pause(1.5)                    # a neutral wall
     hold(*BEFORE, 1.4); pause(0.8)
     cut()

ui/dr-ui/src/develop.rs

@@ -4067,9 +4067,9 @@ impl DevelopSession {
         let space = self.display_space;
         // TRACES: FR-DEV-19c
         // **The one composition that may show a mask.** Every other caller of
-        // the graph — `render_the_file`, the thumbnail, `sample_as_shot` —
-        // goes through `compose_for`, which cannot ask for a reveal, so no
-        // exported file can carry one.
+        // the graph — `render_the_file`, the thumbnail — goes through
+        // `compose_for`, which cannot ask for a reveal, so no exported file
+        // can carry one; `sample_as_shot` composes no operations at all.
         let shader = self.graph.compose_revealing(space, self.reveal().as_ref());
 
         // Rasterise the masks first: the shader addresses array slices by
@@ -4442,18 +4442,28 @@ impl DevelopSession {
         true
     }
 
-    /// The colour at a point with every adjustment taken off, in linear RGB.
+    /// The colour at a point in the space the white balance gains multiply:
+    /// camera RGB with the camera's own balance on, linear, nothing else.
     ///
-    /// **Measured before the chain rather than off the screen**, and that is
-    /// the difference between a picker that converges and one that chases
-    /// itself. The frame on the canvas has already been through the white
-    /// balance being solved for, the tone curve, the contrast and whatever
-    /// else is on; neutralising *that* pixel would be correcting a correction,
-    /// and the second sample of the same wall would land somewhere else. With
-    /// the adjustments stripped the value read is the colour as the file has
-    /// it, which is the domain `neutralise` is defined over.
+    /// **Measured where the operation acts, not where the photographer
+    /// looks.** The white balance node runs first in the chain, on camera
+    /// RGB, before the body's base curve and its matrix; the canvas shows
+    /// the pixel after all three. The probe used to be read off a display
+    /// render with the adjustments stripped, and the solve then treated an
+    /// sRGB triple as if the gains multiplied it directly. On a JPEG the two
+    /// spaces coincide, so it worked; on a raw file from any real body the
+    /// matrix mixes the channels, and a slightly blue wall on a Canon 6D
+    /// came back tint −77 with the whole frame green. This reads the
+    /// camera-space tap a merge stitches from — the sensor's numbers after
+    /// the lens warp — and puts the as-shot balance on itself, which is
+    /// exactly the value the operation's gains are about to multiply.
     ///
-    /// The framing stays on, exactly as it does for [`Self::render_original`]
+    /// That also means nothing has to be stripped and restored: the tap
+    /// runs no operations at all, and the display target is untouched, so
+    /// a sample that found nothing usable leaves the canvas exactly as it
+    /// was.
+    ///
+    /// The framing is the edit's own, exactly as for [`Self::render_original`]
     /// and for the same reason: `x` and `y` are fractions of what is on
     /// screen, and a probe rendered without the crop and the zoom would be
     /// answering about a different part of the photograph.
@@ -4462,41 +4472,23 @@ impl DevelopSession {
     /// averages a small neighbourhood into each of its pixels, which is what
     /// every eyedropper does deliberately: a single photosite off a noisy
     /// shadow is a worse answer than the patch around it, and the photographer
-    /// is pointing at a grey card rather than at a pixel. It is also two
-    /// dispatches' worth of work on a click.
-    ///
-    /// This overwrites the frame the adjust pass is holding, so the caller
-    /// must redraw — which the callback that samples does anyway, since the
-    /// picture has just changed.
+    /// is pointing at a grey card rather than at a pixel. It is also one
+    /// dispatch's worth of work on a click.
     fn sample_as_shot(&mut self, x: f32, y: f32) -> Option<[f32; 3]> {
         /// Long edge of the probe render. See the note above on why it is
         /// small rather than large.
         const PROBE_EDGE: u32 = 192;
 
-        // sRGB regardless of the display: this is a measurement, not something
-        // anybody looks at, and decoding it needs a transfer function known
-        // here. Composing for a wide-gamut panel would put the reading in a
-        // space the arithmetic below does not undo.
-        let space = dr_types::ColourSpace::Srgb;
-
-        let saved = self.graph.state();
-        self.strip_adjustments();
-
         let (sw, sh) = self.demosaiced.size();
         let (fw, fh) = self.graph.output_size(sw, sh);
         let (w, h) = fit(fw, fh, PROBE_EDGE, PROBE_EDGE);
-        let shader = self.graph.compose_for(space);
-        let probe = self
-            .render_with_masks(&shader, w, h, space)
-            .and_then(|()| self.adjust.export_pixels().map_err(|e| e.to_string()));
-
-        // Restored whatever happened, for the reason every other suspension
-        // here restores: leaving the graph stripped after a failed probe would
-        // discard the edit silently.
-        let debt = self.graph.set_state(&saved);
-        self.pay_film_debt(&debt);
-
-        let (rgba, pw, ph) = probe
+        let shader = self.graph.compose_camera_probe();
+        let rendered = self
+            .adjust
+            .render_camera_linear(&self.demosaiced, &shader, w, h)
+            .map(|_| ());
+        let (rgba, pw, ph) = rendered
+            .and_then(|()| self.adjust.read_camera_linear())
             .inspect_err(|e| log::warn!("could not read a neutral off the frame: {e}"))
             .ok()?;
 
@@ -4504,18 +4496,27 @@ impl DevelopSession {
         let px = ((x.clamp(0.0, 1.0) * pw as f32) as usize).min(pw.saturating_sub(1));
         let py = ((y.clamp(0.0, 1.0) * ph as f32) as usize).min(ph.saturating_sub(1));
         let at = (py * pw + px) * 4;
-        let pixel = rgba.get(at..at + 3)?;
+        let pixel = rgba.get(at..at + 4)?;
+        // The tap marks a pixel the lens correction pulled in from outside
+        // the frame with alpha 0. There is nothing there to balance against.
+        if pixel[3] < 0.5 {
+            return None;
+        }
+        // Nor in a clipped one. A blown sky reads as sensor white, and sensor
+        // white with the as-shot balance on is strongly magenta — a solve over
+        // it drives tint to its stop for a pixel that, on the canvas, the
+        // shader has already desaturated to neutral. The same threshold the
+        // shader fades from, so what is refused here is what it would have
+        // hidden there.
+        if pixel[..3].iter().any(|c| *c >= dr_pipeline::CLIP_ONSET) {
+            return None;
+        }
 
-        // The probe was encoded for the screen; the solve is multiplicative
-        // and only means anything in linear light (ARCH §5.2). Undone with
-        // the space's own transfer function rather than a second copy of the
-        // curve written out here.
-        let transfer = space.transfer();
-        Some([
-            transfer.decode(f32::from(pixel[0]) / 255.0),
-            transfer.decode(f32::from(pixel[1]) / 255.0),
-            transfer.decode(f32::from(pixel[2]) / 255.0),
-        ])
+        // The tap is the sensor's numbers with the profile filled neutral;
+        // the operation multiplies them *after* the camera's own balance, so
+        // that goes on here and the solve sees what the gains will see.
+        let wb = self.demosaiced.as_shot_wb();
+        Some([pixel[0] * wb[0], pixel[1] * wb[1], pixel[2] * wb[2]])
     }
 
     /// TRACES: FR-PLAT-AND-5 | NFR-RES-1
@@ -6670,6 +6671,135 @@ mod tests {
         );
     }
 
+    /// TRACES: FR-DEV-3
+    /// The whole point of the picker, measured where the photographer sees
+    /// it: a cast grey on a *raw* frame, sampled, renders grey.
+    ///
+    /// On a raw frame and not a JPEG, because that is where it was wrong. The
+    /// white balance gains multiply camera RGB, before the body's matrix
+    /// turns it into sRGB; the probe was read *after* the matrix, and the
+    /// solve treated the two as the same space. On a body whose matrix mixes
+    /// the channels as much as a Canon's does, a slightly blue wall came back
+    /// tint −77 and the whole frame went green. A JPEG carries an identity
+    /// matrix, so the same test on one passed while the picker was broken.
+    #[test]
+    fn sampling_a_cast_grey_on_a_raw_frame_renders_it_grey() {
+        let Some(ctx) = headless() else { return };
+
+        // A Canon EOS 6D's D65 matrix (rows summing to one, as
+        // `neutral_stays_neutral_through_the_colour_matrix` requires) and a
+        // typical as-shot balance for it.
+        let cam_to_srgb = [
+            1.9125, -1.0587, 0.1461, //
+            -0.2249, 1.6466, -0.4217, //
+            0.0099, -0.5093, 1.4994,
+        ];
+        let as_shot = [1.9, 1.0, 1.7];
+        // What the wall should look like once the camera's own balance is on:
+        // a warm cast, a little over half a stop between red and blue.
+        let balanced = [0.30f32, 0.25, 0.20];
+        let sensor: Vec<u16> = (0..3)
+            .map(|c| (balanced[c] / as_shot[c] * 65535.0).round() as u16)
+            .collect();
+        let size = 64u32;
+        let raw = RawImage {
+            width: size,
+            height: size,
+            data: sensor.repeat((size * size) as usize),
+            cfa_pattern: dr_decode::CfaPattern::Rggb,
+            black_level: [0; 4],
+            white_level: 65535,
+            wb_coeffs: [as_shot[0], as_shot[1], as_shot[2], 0.0],
+            color_matrix: Some(cam_to_srgb),
+            base_curve: dr_decode::BaseCurve::IDENTITY,
+            samples_per_pixel: 3,
+            profile: None,
+            make: String::new(),
+            model: String::new(),
+            crop: dr_decode::CropRect {
+                x: 0,
+                y: 0,
+                width: size,
+                height: size,
+            },
+        };
+        let mut session =
+            DevelopSession::open(&ctx, &raw, dr_types::Orientation::NORMAL).expect("session");
+
+        let at = ((size / 2) * size + size / 2) as usize * 4;
+        let before = read_back(&ctx, &session.render(size, size).expect("render"));
+        let cast = |px: &[u8]| px.iter().max().unwrap() - px.iter().min().unwrap();
+        assert!(
+            cast(&before[at..at + 3]) > 20,
+            "the premise: the wall renders with a cast, {:?}",
+            &before[at..at + 3]
+        );
+
+        assert!(
+            session.sample_neutral(0.5, 0.5),
+            "a mid-grey is a usable sample"
+        );
+
+        let after = read_back(&ctx, &session.render(size, size).expect("render"));
+        let px = &after[at..at + 3];
+        assert!(
+            cast(px) <= 3,
+            "the sampled point should render neutral, got {px:?} with {:?}",
+            session
+                .rows()
+                .iter()
+                .filter(|r| r.value != r.default_value)
+                .map(|r| (r.param_label.to_string(), r.value))
+                .collect::<Vec<_>>()
+        );
+    }
+
+    /// TRACES: FR-DEV-3
+    /// A blown highlight is refused, the way black is.
+    ///
+    /// Sensor white is not a colour: every channel stopped counting, so the
+    /// ratio between them is the as-shot multipliers and nothing about the
+    /// scene. Sampling the overcast sky on a Canon 6D frame drove tint to
+    /// -100 and temperature to -15 for a patch the canvas showed as pure
+    /// white, which is the picker being wrong rather than the point being a
+    /// poor choice. Refused, nothing moves and no step is taken.
+    #[test]
+    fn sampling_a_blown_highlight_moves_nothing() {
+        let Some(ctx) = headless() else { return };
+        let size = 16u32;
+        let raw = RawImage {
+            width: size,
+            height: size,
+            data: vec![65535; (size * size * 3) as usize],
+            cfa_pattern: dr_decode::CfaPattern::Rggb,
+            black_level: [0; 4],
+            white_level: 65535,
+            wb_coeffs: [1.9, 1.0, 1.7, 0.0],
+            color_matrix: None,
+            base_curve: dr_decode::BaseCurve::IDENTITY,
+            samples_per_pixel: 3,
+            profile: None,
+            make: String::new(),
+            model: String::new(),
+            crop: dr_decode::CropRect {
+                x: 0,
+                y: 0,
+                width: size,
+                height: size,
+            },
+        };
+        let mut session =
+            DevelopSession::open(&ctx, &raw, dr_types::Orientation::NORMAL).expect("session");
+        let steps = session.history_rows().len();
+
+        assert!(
+            !session.sample_neutral(0.5, 0.5),
+            "a clipped photosite has no balance in it"
+        );
+        assert!(session.is_neutral(), "and so nothing was corrected");
+        assert_eq!(session.history_rows().len(), steps);
+    }
+
     /// TRACES: FR-DEV-7 | FR-DEV-5
     /// A held comparison hands the edit straight back.
     ///

ui/dr-ui/src/faces.rs

@@ -1069,6 +1069,79 @@ impl Population {
             ids.push(f.face);
         }
 
+        // Not every anchored face enters the scan: each person is stood for
+        // by their references (`dr_face::references`), and the rest of their
+        // faces stay out of the comparison. They keep their place -- they are
+        // in `anchors`, so the pass never releases them -- and they are the
+        // cost that would otherwise grow with every name the user gives.
+        let mut by_person: std::collections::BTreeMap<u64, Vec<usize>> =
+            std::collections::BTreeMap::new();
+        for (i, c) in candidates.iter().enumerate() {
+            if let Some(p) = c.confirmed_person {
+                by_person.entry(p).or_default().push(i);
+            }
+        }
+        let mut keep = vec![true; candidates.len()];
+        let mut anchored = 0usize;
+        for members in by_person.values() {
+            anchored += members.len();
+            // Only a person over the cap loses anyone: under it, `select`
+            // returns every eligible face, and the ineligible are kept too,
+            // since a short vector was a probe before and still is.
+            if members.len() <= dr_face::references::MAX_REFERENCES {
+                continue;
+            }
+            let embeddings: Vec<&[f32]> = members
+                .iter()
+                .map(|&i| candidates[i].embedding.as_slice())
+                .collect();
+            let quality: Vec<Option<f32>> =
+                members.iter().map(|&i| candidates[i].quality).collect();
+            let chosen = dr_face::references::select(
+                &embeddings,
+                &quality,
+                dr_face::references::MAX_REFERENCES,
+            );
+            for &i in members {
+                keep[i] = false;
+            }
+            for &k in &chosen {
+                keep[members[k]] = true;
+            }
+            // A person none of whose faces is long enough to vouch is still
+            // a person, and a pass they had no anchor in would file their
+            // next face as a stranger. The longest stand in.
+            if chosen.is_empty() {
+                let mut by_quality = members.clone();
+                by_quality.sort_by(|&a, &b| {
+                    let qa = candidates[a].quality.unwrap_or(0.0);
+                    let qb = candidates[b].quality.unwrap_or(0.0);
+                    qb.total_cmp(&qa).then(a.cmp(&b))
+                });
+                for &i in by_quality.iter().take(dr_face::references::MAX_REFERENCES) {
+                    keep[i] = true;
+                }
+            }
+        }
+        let left_out = keep.iter().filter(|k| !**k).count();
+        if left_out > 0 {
+            let mut i = 0;
+            candidates.retain(|_| {
+                i += 1;
+                keep[i - 1]
+            });
+            let mut i = 0;
+            ids.retain(|_| {
+                i += 1;
+                keep[i - 1]
+            });
+            log::info!(
+                "references: {} of {anchored} anchored face(s) stand for {} people; {left_out} left out of the scan",
+                anchored - left_out,
+                by_person.len(),
+            );
+        }
+
         Ok(Self {
             cal,
             candidates,
@@ -2121,6 +2194,45 @@ mod tests {
         assert_eq!(after[0].suggested_faces, 3);
     }
 
+    /// A person over the reference cap is stood for by a chosen few, and the
+    /// rest of their faces stay where they are: not compared, not released,
+    /// and still theirs when the next face arrives.
+    #[test]
+    fn a_well_covered_person_is_stood_for_by_their_references() {
+        let many = dr_face::references::MAX_REFERENCES + 50;
+        let catalog = catalog_with(many + 1);
+        for i in 0..many {
+            put_face(&catalog, i as u64 + 1, 0, 1.0 - (i as f32) * 1e-3);
+        }
+        recluster(&catalog, TEST_MODEL, &FaceSettings::default()).unwrap();
+        let him = faces::people(catalog.connection()).unwrap()[0].id;
+        faces::rename_person(catalog.connection(), him, "Ian").unwrap();
+
+        // Every one of his faces lies in one plane, so two references span
+        // them all and the selector stops there rather than filling the cap.
+        let pop = Population::read(&catalog, TEST_MODEL).unwrap();
+        let standing = pop
+            .candidates
+            .iter()
+            .filter(|c| c.confirmed_person.is_some())
+            .count();
+        assert!(
+            (2..=dr_face::references::MAX_REFERENCES).contains(&standing),
+            "{standing} of {many} faces entered the scan"
+        );
+        assert_eq!(pop.anchors.len(), many, "the rest lost their anchor");
+
+        put_face(&catalog, many as u64 + 1, 0, 0.98);
+        recluster(&catalog, TEST_MODEL, &FaceSettings::default()).unwrap();
+        let after = faces::people(catalog.connection()).unwrap();
+        assert_eq!(after.len(), 1, "a second Ian appeared: {after:?}");
+        assert_eq!(
+            after[0].suggested_faces,
+            (many + 1) as u64,
+            "faces were released"
+        );
+    }
+
     /// `dr-types` sits below the face engine and cannot name its constant, so
     /// it restates the number. This is the thing that stops the two drifting:
     /// a settings page marking 0.80 as "default" while the engine had moved to

ui/dr-ui/src/lib.rs

@@ -3127,14 +3127,12 @@ pub fn run(paths: Vec<PathBuf>) -> Result<()> {
                 .borrow_mut()
                 .as_mut()
                 .is_some_and(|s| s.sample_neutral(x, y));
+            // Nothing to redraw otherwise: the probe renders to its own
+            // target and a sample that found nothing usable moved nothing.
             if sampled {
                 sync_rows(&w, &rows, &session);
+                redraw(&w);
             }
-            // Redrawn either way. A sample that found nothing usable still
-            // overwrote the frame the adjust pass was holding, and leaving the
-            // canvas showing a probe of the unedited image would look like the
-            // edit had been thrown away.
-            redraw(&w);
         });
     }