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Upstream (NegPy) review log

SwiftInvert ports NegPy's negative-inversion pipeline; NegPy (~/Documents/code/NegPy) keeps evolving. This file records the last NegPy commit we reviewed, so "what changed since we last looked?" always has a baseline. Keep it current: every upstream review ends by updating the marker and appending a history entry.

Last reviewed

commit:   8d6f44e  ("SANE/pieusb: RGBI + NegPys IR dust removal (#583)")
reviewed: 2026-07-21
fixtures: Tests/Fixtures/ dumped from 96adfde (2026-07-20, Adobe RGB world) —
          still valid; nothing in 96adfde..8d6f44e touches the pipeline.

How to run a review

Preferred: run the /negpy-review skill (.claude/skills/negpy-review/) — it automates the steps below, applies the port/skip judging rules, and updates this file. The manual procedure, for reference:

  1. cd ~/Documents/code/NegPy && git fetch origin
  2. git log --oneline <last-reviewed>..origin/main — the unreviewed range.
  3. Focus the diff on the pipeline we track: git diff <last-reviewed> origin/main -- negpy/features/exposure/ negpy/features/process/ negpy/kernel/image/ (normalization.py, logic.py, models.py/EXPOSURE_CONSTANTS, the WGSL shaders). Also check whether the characterization goldens moved (tests/test_scene_linear_relocation.py, tests/test_characteristic_curve.py) — golden changes mean a deliberate default-look change upstream.
  4. Decide per change: port / deliberately skip (record why) / not applicable (UI, camera capture, CPU-parallelism, stages we don't ship).
  5. If constants or kernel semantics were ported: pull NegPy, re-dump fixtures (uv run python ~/Documents/code/SwiftInvert/scripts/dump_fixtures.py from the NegPy repo — check the dump script against upstream signature changes first), update K / kernels, make test.
  6. Update the Last reviewed marker and append to the history below.

Review history

2026-07-21 — through 8d6f44e (0.39.0-dev, 21 commits)

Kernel status: untouched — a genuine null. The path-filtered log over features/exposure/, features/process/, kernel/image/ and the characterization goldens is empty; no renames in the range; the pipeline-tree diff is empty. No fixture re-dump, no constants drift, dump_fixtures.py unaffected. The range is film-scanner integration (Coolscan/SANE bba487d, RGBI + IR dust over SANE 8d6f44e), IR dust reconstruction rework (f612a74), lab sharpen improvements (d3436c7 — stage we don't ship), multi-part scan stitching (5e141df — capture-side composite assembly), contact-sheet/DB/UI work, and docs churn.

Noted for the active crosstalk thread (not a pipeline change): a27f035 widens the crosstalk matrix adjustment range in their EDITOR dialog by one line — the matrix math is untouched. Confirms the Density Mixer remains manual upstream; the chart-based auto-solve being planned here (negcli chart-solve, see 2026-07-20/21 conversations) stays a SwiftInvert-original with no upstream counterpart to converge with yet.

Not applicable: 2d8e55e TIFF sRGB decode gating (their TIFF ingestion; we're camera-RAW only), 67e2051 scan-window exposure gating, ce28dc1 DB dialog, 9c260e2 contact-sheet labels, 2cdc569 filmstrip thumbnails, b805578 icon/migration fixes, readme/changelog/tutorial commits.

2026-07-20 — through 2cdc569 (0.39.0 → 0.40.0, 9 commits)

Kernel status: untouched. Zero commits in the range touch features/exposure/, features/process/, kernel/image/, or the characterization goldens — the path-filtered log AND git diff --stat over those trees are empty, and there are no renames in the range (--diff-filter=R empty). The shared-kernel-adjacent hunks were checked by hand: lab.wgsl + lab/logic.py/models.py changed ONLY the sharpen block (rewritten for the 0.40.0 sharpening feature — zero lines touch vibrance/ saturation/Dye Mute or the Lab matrices our colorPop mirrors), and the domain/models.py hunks are sidecar migrations for features we don't ship (IR inpaint radius, filed-carrier toggle fold). No fixture re-dump, no constants drift; dump_fixtures.py signatures unaffected (exposure normalization.py/logic.py unchanged).

Ported: nothing (nothing required).

Divergence baseline moved (no action): d3436c7 rebuilt sharpening — Method selector (Unsharp Mask with halo-suppression overshoot clamp + gradient Masking, or Richardson-Lucy deconvolution on linear Y applied as a chroma-preserving RGB ratio), Radius/Masking sliders, preview/export parity via shared gaussian_kernel_1d taps (the old fixed 5×5 GPU kernel sharpened the wrong band at export scale). We don't ship sharpen (recorded divergence); if it's ever implemented, port THIS version (PIPELINE.md §5.4 documents the full math). Default sharpen stays 0.25.

Noted upstream self-doubt on Dye Mute (strengthens our skip): PIPELINE.md now carries "(The default was tuned against the old ProPhoto working gamut — it may run strong now that the working space is Adobe RGB.)" — upstream themselves flag the 0.5 default as possibly too strong post- b3490eb. Our 2026-07-17 skip stands; reopening condition unchanged (visible oversaturation at hard grades on real rolls).

UI idea worth copying independently (not pipeline): b805578's analysis-region active-indicator — a small dot on the Freedraw Analysis Region button whenever a custom region is overriding the buffer. We have the same override semantics (resolve_analysis_region port) and the same discoverability gap after the tool closes.

Not applicable: a27f035 crosstalk matrix range (stage we don't ship), bba487d Coolscan/SANE film scanning (capture stack), f612a74/8a98326 IR dust reconstruction (retouch; runs pre-normalization on IR-carrying scans — we're camera-RAW only, no IR plane), d3436c7's non-sharpen bulk (their GPU engine sharpen-pass plumbing), c3e83ff tooltips, b805578's icon fixes/carrier migration, c53aa26 USER_GUIDE rewrite, 2cdc569 filmstrip thumbnail fixes.

Still open (carried over): 91a1b78 user-tunable Auto Density / Auto Grade targets — blocked on us growing a Settings surface; the on-scan Color Mixer band re-tune pass (ours, post-b3490eb).

2026-07-19 — through 96adfde (0.38.0 → 0.39.0-dev, 19 commits)

Seven pipeline-relevant commits — the deepest range since the original port, headlined by a full working-space swap.

The headline: b3490eb Adobe RGB (1998) working space. Upstream REVERSED the 2026-07-16 ProPhoto output fix: full ProPhoto primaries at output are now judged "unnaturally saturated, pain to correct", and the whole pipeline boundary moved to Adobe RGB — OETF ROMM TRC (1.8 + linear toe) → pure 563/256 gamma (no linear segment), output tagging, Lab matrices, CLAHE/toning shaders, display/export management, ALL goldens regenerated. Dye Mute stays at default 0.5 on top, so their canonical look is now markedly more muted than either the pre-fix or the ProPhoto-era look. Third output-space change in four days (stale Adobe RGB bug → ProPhoto

  • Dye Mute → deliberate Adobe RGB).

Judgment (revised 2026-07-20 after researching issue #537 / PRs 518/538/544): the "third change in four days" framing was wrong — this is NOT a flip-flop. NegPy's output had been Adobe-RGB-interpreted for its whole life via a stale tag; PR #518 exposed true ProPhoto for the first time, two independent users immediately reported neon reds AND hue shifts (red→magenta, sky→cyan) with image evidence, Dye Mute could damp chroma but not hue, and #544 restored Adobe RGB coherently (primaries + pure 563/256 TRC + D65) within three days. The argument (user thetalkingdrum, adopted verbatim by the maintainer): the pipeline ASSIGNS primaries to raw uncharacterized sensor RGB at output — an interpretation, not a conversion — and ProPhoto's imaginary green/blue primaries stretch dye separations outside the spectral locus. Decision is settled upstream (both reporters confirmed the fix; follow-ups are routed to crosstalk characterization).

The argument applies to SwiftInvert verbatim — we tag sensor-native pipeline output as ROMM the same way — and one of our own divergences may be evidence: redHue +0.5 exists because "C-41 reds skew magenta out of the box", which matches the reported ProPhoto-interpretation hue shift exactly. A correct-primaries output might let redHue return toward 0. PORTED 2026-07-20 — the user chose convergence over A/B ("I want to stay close to the main project"). Full port: WorkingOETF → pure 563/256 gamma (Swift + MSL 0.45470693 literal), Lab matrices/white → Adobe RGB D65 both sides, output tagging → adobeRGB1998 (ImageConversion, ColorIO workingColorSpace, negcli TIFF), littleCMS oracles regenerated from NegPy's AdobeCompat-v4/sRGB-v4 at 96adfde, fixtures re-dumped from 96adfde (dump script adapted to the paper_black rename, manifest key stable), coupled constants ported (anchor 0.75, grade target 0.6, strength 0.5). Space-sensitive tests recalibrated with intent preserved: True Black's contract restated in the linear domain (the old encoded thresholds baked in the ROMM toe), pre-saturation chroma margin 1.05 → 1.02 (smaller-gamut Lab), mixer-band test pixel moved in-band (real- content blues land 240–265° in the new Lab — the band constants themselves survive). ExportColorSpace's wide option relabeled Adobe RGB (case name kept for sticky-JSON compat). Export-note: existing exports re-render slightly different, as upstream's changelog warns. Follow-ups: redHue +0.5 RETIRED same day (it countered the hue skew this port removes at the root; default 0 again, explicit sidecar values preserved); the on-scan mixer-band re-tune pass remains open. 132 tests green incl. GPU parity against Adobe-world fixtures; bench unchanged.

Coupled to the above — do NOT port separately: 2db0470 + 088c393 auto-constant tunings (anchor_target_density 0.74 → 0.75, auto_grade_target 0.55 → 0.6, auto_grade_strength 0.3 → 0.5, goldens moved). These were tuned against the Adobe RGB output; applying them under our ROMM output applies their new-space taste to our old-space look. Port together with b3490eb or not at all.

Ported (2026-07-20) — we shared the bug: 2125a34 Cast Removal neutral axis vs PRE-trim bounds. Their CPU measured the neutral axis against user-trimmed (WP/BP-adjusted) bounds while their GPU measured pre-trim; they standardized on pre-trim ("the film's inherent cast is a source property — creative trims shouldn't perturb it"). Our finalize had faithfully ported the now-declared-buggy CPU side. Ported as the simplification it implies: finalize/analyze lost their offset params (the analysis is now fully offset-independent; offsets fold into finalBounds at derive time only), ImageSession's second cache tier (AnalysisKey) dissolved — wp/bp handle drags re-run no analysis at all — and ImagePipelineSeamTests pins the new semantics (axis == base-bounds measurement; offsets still reach the render). Fixtures unchanged (all dump configs use zero offsets); CLAUDE.md §2 updated.

To port (proposed, needs a Settings surface + the visible-improvement bar): 91a1b78 user-tunable Auto Density / Auto Grade targets — app-global calibration (TUNABLE_TARGETS ranges over 5 anchor/grade constants, Set Targets dialog, TARGETS_REVISION cache-bust). The right shape for per-scanner calibration; we have no Settings window yet (TODO).

Bookkeeping (no action): 687bcd5 True Black renamed Paper Black, inverted — new default (off) keeps BPC on, so upstream's effective default still matches ours; only nomenclature/polarity changed. Our trueBlack field and UI naming stand; renaming to match upstream is a cosmetic option, recorded here so the next review doesn't re-derive the polarity mapping (paper_black = !bpc).

Not applicable: 81bea3c half-frame mode (their asset/session model), 4678569/96adfde camera-scanning fixes, 7e888ef dodge/burn mask visibility, 13a7ba5/3113241 update banner, b14dc62 tutorial, docs/changelog/roadmap churn (a11535f 18f6dd5 7a0046d 46c85c2 c27b379 5bd0c03 57948f5 0ca43de-style lint).

dump_fixtures.py: BROKEN against ≥b3490eb — _oetf_encode_flat/ _oetf_decode_flat lost their break-point parameters and the OETF semantics changed; the closed-form working_oetf fixture case would dump Adobe-gamma values against our ROMM oracle. Verify/adjust the script BEFORE any re-dump past b3490eb (it still works at ≤6b841a1 checkouts).

2026-07-17 — through 0ea27d2 (0.38.0 tail, 6 commits)

One pipeline-relevant commit, and it's a golden move: 8bc9678 Dye Mute — grade-coupled chroma damping, ON by default upstream (0.5), relocation goldens regenerated. Mechanism: damp = (slope_min/slope_g)^strength (green reference slope, clamped) folded into the Lab saturation multiplier at parameter-derivation time — per-channel print curves multiply channel separation by the slope, so chroma inflates with grade; the damping counters it ("mimicking paper dyes' unwanted absorptions"). No WGSL/uniform change upstream; the identical fold works here (colorPopActive reads derived params, so params.saturation × damp self-activates the pass). Port cost ~15 lines + tests, NO fixture re-dump (derivation-side; apply_saturation unchanged). dump_fixtures.py signatures unaffected (new function only).

Deliberately skipped (for now) — reopening condition recorded: Dye Mute is not ported despite being a golden move. Their motivation was a regression fix: the ProPhoto output bug had been squeezing their gamut for releases; fixing it (07e3f8f) suddenly exposed full-gamut chroma their users never saw, reading oversaturated at hard grades. We never had the bug — our color has been full-gamut ProPhoto from day one, and our deliberate divergences (preSaturation 1.15, redHue +0.5) were A/B-tuned ON that gamut toward MORE color, not less. Adopting their 0.5 default would desaturate our established default look ~15% at typical grades (up to ~55% at slope 10); adopting the slider at 0 would add exactly the kind of dormant control the 2026-07-16 removals just cleared out. Reopen if hard-grade frames ever visibly oversaturate on real rolls — the mechanism above is the ready-made fix, and one negcli A/B decides the default.

Also in 8bc9678: default lab sharpen 0.5 → 0.25 (we don't implement lab sharpen — divergence note updated in CLAUDE.md).

Not applicable (this range): 5811662 crop-ratio picker consolidation (their UI; NOTE their final ratio list — 7:5, 16:9, 16:10, US Letter — as reference for our own TODO'd aspect presets), 611b251 Finish/geometry sidebar cleanup + auto-narrowband-on-RGB-scan (capture-side scanning stack), 0ca43de lint, 1c07529 tooltips, 0ea27d2 changelog. Changelog-only item: "Cast Removal strength sticks across frames" is their session-sticky settings model — ours is per-image sidecars + explicit Copy/Paste, an architectural divergence, not a gap.

2026-07-16 — through 4a669ed (0.38.0 → unreleased, 9 commits)

Kernel status: untouched. Zero commits in the range touch features/exposure/, features/process/, kernel/image/, or the characterization goldens — the path-filtered log is empty, git diff --stat over those trees returns nothing, and there are no renames in the range (--diff-filter=R empty). A genuine null for the inversion pipeline: no fixture re-dump, no constants drift, dump_fixtures.py signatures unaffected. The one shared-kernel-adjacent hunk was checked by hand: lab.wgsl changed only a stale comment ("Adobe RGB" → ProPhoto/D50 — the code fix was 07e3f8f, reviewed 2026-07-15), and the lab/logic.py rewrite is entirely the CLAHE function; vibrance/saturation (mirrored by our colorPop) are untouched.

Ported: nothing (nothing required).

Not applicable (this range):

  • 232f26d unify CPU/GPU CLAHE into one Lab-L algorithm (+ new test_gpu_curve_parity CLAHE case, PIPELINE.md now documents CLAHE as its own stage before Retouching) — local-contrast lab stage we don't ship. If we ever add local contrast, port THIS version (fixed 8×8 tile grid, 256 bins, integer-count clip + even redistribution, smoothstep-bilinear CDF blend on CIELAB L*, CPU/GPU pinned to ~1e-6).
  • c714a24 Feat/finish — Finish panel: edge burn (true exposure burn in stops, radial↔rectangular roundness), filed-carrier black rebate, print mats — print-finishing stage, out of scope. The edge burn design (stops-domain I·2^(−s·m), card-burn roundness) is the note-worthy idea if a vignette tool is ever wanted.
  • 78b74ef roll-aware Auto Crop All + consensus detection (~500 lines in geometry/batch_autocrop.py + big geometry/logic.py growth) — camera-scan auto-crop detection; we have no auto-crop detection feature.
  • 16bcee8 DNG/JXL export via imagecodecs 16-bit CMS — their export CMS stack; we export JPEG/TIFF through ImageIO/ColorSync.
  • 4a669ed export_fmt/color_space override in all_saved scope — their export-preset session plumbing.
  • 2682a0a camera-scanning calibration fix; 69a2934 status toasts / crop busy overlay; ca18ecb overflow-menu fix; 86e73ba changelog — UI/capture.

2026-07-15 (second review) — through 6b841a1 (0.38.0 tail, 9 commits)

Kernel status: DEFAULT LOOK MOVED UPSTREAM. Three commits (0f063cc, 67b5a8c, 6b841a1) changed exposure/models.py and regenerated both characterization goldens — the highest-priority signal this log tracks. Net change at the tip (0f063cc bounced auto_grade_target to 0.6, 67b5a8c back to 0.5, 6b841a1 settled it):

  • paper_dmin default True → False (paper white d_min 0.06 → 0; highlights print brighter — goldens moved 0.86 → 0.94 in the lights).
  • true_black default False → True — upstream converged on OUR recorded divergence. No code change here; the CLAUDE.md divergence entry ("trueBlack default on; NegPy ships it off") is now stale and should be dropped when the port lands.
  • EXPOSURE_CONSTANTS["auto_grade_target"] 0.5 → 0.55, ["auto_grade_strength"] 0.4 → 0.3 — Auto Grade targets slightly higher contrast and adapts less to scene range. Maps to K.autoGradeTarget / K.autoGradeStrength (ExposureConstants.swift:67-68), CPU-only (no MSL duplicate). Also shifts CurveLogic.defaultGradeRange 1.0 → 1.1, the denominator of the Negative-character read-out — upstream's stats._negative_row uses the same default_grade_range(), so porting the constant keeps that diagnostic in lockstep automatically.

Ported (2026-07-15, same day as the review):

  1. K.autoGradeTarget 0.5 → 0.55, K.autoGradeStrength 0.3 (ExposureConstants.swift — CPU-only, no MSL duplicate). Shifts CurveLogic.defaultGradeRange 1.0 → 1.1, which the Negative-character read-out tracks automatically (verified via negcli meter on a real CR3: "density range 0.958 default grade range 1.100 → normal").
  2. ExposureSettings.paperDmin default true → false, including the sidecar decoder fallback (user's call: no existing edits worth preserving, so no split-default dance). negcli meter confirms the paper floor is gone — brightest tone reads D 0.00 (was 0.06 = K.dMin).
  3. trueBlack: no code change (already our default); the CLAUDE.md divergence bullet is retired — it's upstream's default now too.
  4. Fixtures re-dumped from 6b841a1. dump_fixtures.py now records true_black in the per-config manifest (it already recorded paper_dmin), and both parity harnesses (AnalysisParityTests.settingsFrom, GPUParityTests.settings) read it instead of hard-coding the old NegPy default — future default flips on either side can't silently skew parity. Drift-catcher mutation lists (SidecarCodecTests, HistoryLabelTests) updated for the new paperDmin default. All 132 tests pass; negcli bench unchanged (4.4 ms/frame, prepare 157 ms, finalize 25 ms).

Deliberately skipped:

  • Lab sharpen default 0.25 → 0.5 + the lab.wgsl sharpen rework (0f063cc: real CIELAB L*-space unsharp mask with reflect-101 borders, sigma tracking scale_factor, smoothstep noise gate — replacing the old gamma-luma RGB-ratio scale). We don't ship sharpen (recorded divergence). Divergence baseline moved: if sharpen is ever implemented, port THIS Lab-space version, not anything older.

Not applicable (this range):

  • f309982 cast-removal strength sticks across frames, 6e55a4a True Black sticks across frames — their Qt session's frame-to-frame settings carry-over; we have per-image sidecars + Copy/Paste Adjustments, no carry-over model.
  • 07e3f8f colour-manage from the working space, not Adobe RGB — their AppState.workspace_color_space was left at "Adobe RGB" when the working space moved to ProPhoto, skewing preview/export/thumbnails together. SwiftInvert has no such field: display tags rommrgb directly, export draws ROMM into an sRGB context; ColorIOTests oracles were generated directly from NegPy's bundled ProPhoto ICC (not through their AppState path), so they are unaffected. Their deleted detect_color_space_from_raw was never ported.
  • 936ff88 untagged scanner-TIFF loading (sRGB → linear scanner data), 34e9efe TIFF export via imagecodecs 16-bit CMS — scanner-TIFF input and their export CMS stack; we're camera-RAW only and export through ImageIO/ColorSync.
  • 3a0175c Feat/heal — retouch (out of scope); its rawpy_loader.py hunk is the VueScan/Adobe SubIFD LinearRaw scanner-DNG path, also out of scope (camera DNGs go through LibRaw unaffected).

2026-07-15 — through ecec2bb (0.37.2 → 0.38.0, 7 commits)

Kernel status: untouched. Zero commits in the range touch features/exposure/, features/process/, kernel/image/, or the characterization goldens — the path-filtered log is empty and git diff --stat over those trees returns nothing. No renames in the range (--diff-filter=R empty; all tracked pipeline files still present at the tip), so this is a genuine null, not a path-filter miss. No fixture re-dump, no constants drift, dump_fixtures.py signatures unaffected. 0.38.0 is entirely triage/UI/workflow work.

Ported: nothing (nothing required).

Closed since the last review (were in "To port", now shipped here independently of upstream):

  • Fine rotation + Straighten (7f4b7a7) — shipped as our unified Crop & Straighten mode (CropGeometry, commitFineRotation), a Lightroom-model design rather than upstream's reference-line tool.
  • "Enter confirms crop" (3961b4d) — shipped (fa5c890), plus Escape-cancel.

Correction to this entry (same day): the TIFF-compression item below was first logged as "confirmed still absent". That was wrong. TIFF compression has been implemented since a499904 — Exporter.swift sets kCGImagePropertyTIFFCompression = 5 (LZW), and its comment already records the deliberate LZW-over-Deflate decision (ImageIO's Deflate support is undocumented). The false "confirmed" came from a verification grep truncated by head -12, forty lines before the relevant code. Item closed, not open. Lesson for future reviews: never head-truncate an absence check — absence is exactly what truncation fabricates.

Closed (was carried over as "To port"; already shipped here):

  • TIFF export compression (fb4b7a7) — done at a499904 (LZW). Upstream's Deflate+predictor is a deliberate skip, not a gap: ImageIO won't reliably write Deflate TIFF. Do not re-raise without new evidence.

Ported (2026-07-15, same day as the review):

  • 77c8113 spot densitometer + zone strip → NegativeKit/Densitometry.swift (zone(ofEncoded:), printDensity(ofEncoded:), read(encodedRGB:), zoneRoman), SwiftInvert/Densitometer.swift + DensitometerReadout.swift, wired to a canvas hover in DetailView with the read-out in the control bar. NegPy-exact semantics, including luma-on-encoded before the OETF decode. Divergence from upstream, deliberate: the probe reads the displayed rgba8 bitmap (already ROMM-encoded) instead of a GPU metric — upstream needs density_hist.wgsl to feed their H&D chart; we have no chart, so a 120-bin GPU pass would have no consumer. density_histogram therefore not ported; revisit only if we ever build the H&D chart. Also skipped: the ΔD-above-base per-channel figure — it needs the source linear pixel + bounds, i.e. an actor round-trip into ImageSession per pointer move, for the negative-diagnostic half of the read-out. D + zone is the darkroom core; ΔD is a candidate if the round-trip proves cheap.
  • Negative character diagnostic → Densitometry.character(densityRange:) (NegPy's 0.80/1.25 gates and wording), shown under the Grade slider — the slider it's about. Reads analysis.baseBounds.luminanceDensityRange, verified to be the same norm_density_range upstream feeds both its curve and this diagnostic.
  • Both are pure measurement (no render path), so the parity fixtures are untouched and no re-dump was needed. 92 tests pass, including a new DensitometryTests suite of closed-form oracles.
  • Verified on real scans via a new negcli meter command: on three CR3s the brightest tone reads D 0.06 on every frame — exactly K.dMin, the paper white the pipeline targets — and the character gates fire correctly (0.902 → normal, 0.710 / 0.494 → flat).
  • Unverified: the hover interaction itself — verified by hand 2026-07-15: hovering the canvas meters correctly. (The original gap: synthetic mouse events can't reach the unbundled binary — no accessibility permission, app won't take focus from a shell — and the known-working histogram hover ignored them too, proving the harness was what failed. Lesson kept: GUI hover paths in this app need a human pointer to verify.)

New candidate (perf/architecture, not pipeline) — half ported, half declined:

  • 938fe9e "halve preview-load memory; instant frame switching". Ported: multi-frame retention — AppModel.sessionLRU keeps the 2 most recent ImageSessions (upstream's preview_cache_max_full_res_entries budget: active frame + the one navigated from), with releaseHQ() stripping the full-res tier from the frame that isn't on screen. Retention alone suffices here because every cache tier is already keyed. Declined: upstream's RenderMemo — it memoizes the last displayed render because their re-render is expensive. With the tower warm ours is derive+GPU (~5 ms), so a memo of the CGImage would add a staleness surface (their key has to track HQ flag, working space, GPU engine, soft-proof ICCs, monitor profile) to save 5 ms. Not worth it. Declined: copy elision — their win was deleting numpy defensive .copy() calls. Swift arrays are COW, so we never had that class of waste; the one place it would matter is already explicit (preview = meterPreview at 0°, commented "COW: at 0° the render input IS the meter image, no copy"). No change made. Original analysis of both ideas, retained for context:
    1. Multi-frame retention. Upstream gives full-res cache entries a slot budget (default 2: active frame + the one navigated from) so navigate-back is instant, and memoizes each frame's last displayed render in a new RenderMemo keyed by config + every display-path input, painting from it immediately while the authoritative render refreshes underneath. We hold exactly one ImageSession (AppModel.swift:506 reassigns a single optional), so navigating back drops the entire cache tower — decode, oriented preview, Prepared (~150 ms), textures — and rebuilds from scratch. A 2-slot session LRU would be the bigger win for us than the memo itself, since we discard more than they do. Wants a memory-budget check first (our HQ path already caches a full-res decode per session).
    2. Copy elision under a read-only contract. They removed three redundant full-size buffer copies (peak RSS 2880→1609 MB on a 56 MP load) by letting cache and caller alias one buffer. Less directly applicable — our RGBImage copies are value-semantic and our contract already forbids handing out live textures — but worth a look at the HQ decode path if HQ memory ever becomes a complaint.

Not applicable (this range):

  • 976851c UI refinements; ecec2bb panel pin/reset docking; 979b592 adaptive canvas-toolbar overflow — their Qt dock/panel layer.
  • 13b9434 heal/scratch edits never persisted — retouch, not shipped here.
  • 2079d7c docs (their CLAUDE.md slim-down); 0ca292d CI self-assign workflow.
  • 0.38.0 changelog headliners we don't ship: Keep/Reject contact-sheet triage, unreadable-file badges, roll-wide undo, canvas-tool Esc grammar, colour/ Filtration renaming. One idea worth noting even though the feature is out of scope: their two-stage Esc (first clears in-progress points, second puts the tool down) — our Escape already cancels Crop & Straighten wholesale, which is the right behaviour for a mode with no in-progress point list.

2026-07-14 — through 0500404 (0.37.1–0.37.2, 7 commits)

Kernel status: untouched. No commits in the range touch features/exposure/, features/process/, kernel/image/, or the characterization goldens — no fixture re-dump, no constants drift, dump_fixtures.py signatures unaffected.

Ported: nothing (nothing required).

Not applicable (this range):

  • 2ecaebb GPU readback-vs-destroy race fix (per-texture lock in their wgpu GPUTexture; densitometer hover on the UI thread raced engine cleanup on file switch). SwiftInvert's architecture already precludes this class of bug: RenderPipeline.render is serialized by an internal lock and returns read-back buffers, never live textures. Note for the future: if we port the spot densitometer (flagged 2026-07-13), keep hover readouts on those read-back buffers, not on GPU probes.
  • c728874 more ASCII-encode EXIF crash fixes — their metadata writer.
  • 2a62c6a camera-scanning follow-ups (RGB-only Scanlights, live-view polish, crash logging) — feature we don't ship.
  • 3961b4d UX polish (drag-to-heal, Enter confirms crop, cursor/tooltip tweaks) — heal is out of scope; "Enter confirms crop" is a small UX idea we could copy independently of upstream.
  • a033b92, 80041ca, 0500404 — changelog/lint churn.

To port (proposed, not yet implemented — carried over from 2026-07-13, re-confirmed still open):

  • TIFF export compression (fb4b7a7, upstream default Deflate+predictor): our Exporter.swift still writes uncompressed TIFF. Best-value small item; verify ImageIO Deflate support, else LZW.
  • 77c8113 spot densitometer + density_histogram metric + zone strip — useful darkroom tool we lack; moderate effort (new GPU metric + UI), no parity impact.
  • "Negative character" diagnostic (flat/contrasty vs default_grade_range()) — cheap, blocked on us having a stats read-out surface.
  • Fine rotation + Straighten tool (7f4b7a7) — geometry feature, not pipeline; still open as a feature candidate.

2026-07-13 — through f279337 (0.37.0 release, 25 commits)

Kernel status: untouched. No changes to normalization/curve logic, EXPOSURE_CONSTANTS, or the characterization goldens — no fixture re-dump needed. Only two commits touched features/exposure/ at all:

Ported: nothing (nothing required).

Candidates flagged (not yet decided):

  • 77c8113 Analysis panel: merged H&D chart, spot densitometer, zone strip. New density_histogram metric (120 bins over −0.1…1.1 normalized-log density, analysis.py/density_hist.wgsl) computed per render; the densitometer maps hover → normalized-log coords → zone/density read-out. Presentation-layer, but a genuinely useful darkroom tool we lack.
  • stats.py rework (same PR): "Negative character" diagnostic — measured density range vs default_grade_range(), ratio <0.80 → "flat (≈N−1)",

    1.25 → "contrasty (≈N+1)". Cheap to add if we grow a stats read-out.

  • fb4b7a7 default TIFF compression LZW → Adobe Deflate (ZIP) + horizontal predictor. Our export currently writes uncompressed TIFF (no compression options set in Exporter.swift); worth adding compression, though ImageIO's Deflate-TIFF support needs verifying (LZW is the safe bet).
  • 7f4b7a7 clockwise-positive fine rotation + Straighten reference-line tool — we only have 90° steps; geometry feature, not pipeline.

Not applicable / out of scope:

  • db72e9f CPU/GPU parity for B&W renders (post-curve luma collapse in exposure.wgsl is mode == 1 only; we don't ship B&W). Its histogram sub-fix (bin from float output before quantization, drop the 4× stride) is a CPU-preview artifact fix — our histogram256 already bins the linear float content on GPU.
  • e56c199 preserve edits when EXIF rewrites change the file hash — NegPy keys sidecars by content hash; ours are filename-keyed.
  • 1deeba6 batch export path/mode bug — their session-export plumbing.
  • Toners (4a3cd34), crosstalk profile editor (0bba263), retouch/heal & dust (9b04f49, 05b8763), dodge-burn masks (2cf6afd), camera scanning (c558a16, 15d15c7), shortcut-editor UI (4 commits), EXIF string sanitizing (8363495), changelog/screenshot churn — all stages/features we deliberately don't ship.

2026-07-11 — through cac6396 (v0.35 → v0.36 era, ~20 commits)

Ported:

  • True Black (BPC): t → (t−b)/(1−b), b referenced to physical d_max; negative toe raises the clip point. (SwiftInvert later defaulted it ON — our divergence; NegPy ships it off.)
  • toe_height 0.35 → 0.90 with toe_grade_strength × 0.35/0.90 rescale (perceptual toe/shoulder balance; default output bit-compatible).
  • Cast removal: confidence scaling always on (auto toggle removed).
  • flare/surround deleted (were always-off in SwiftInvert).

Deliberately skipped:

  • Per-layer R/G/B trims (grade/toe/shoulder/width/Snap) — per-channel crossover correction; candidate future feature.
  • Split Grade + Zone Density — upstream's convergent equivalent of our tone controls (theirs: zone centers 1.49/0.34, sharpness 4.0, sequential ordering; ours keep 1.40/0.30 @ 3.5 with documented monotone bounds).
  • Midtone-gamma user slider (cheap to add if wanted).
  • C41 denoise (lab stage — not ported), multi-core CPU kernels (we're GPU), camera-scanning feature work.

Known-unreviewed at time of writing: local NegPy has already pulled past the marker (14 commits, cac6396..c558a16, mostly camera-scanning work by the titles) — NOT yet reviewed for pipeline changes.

2026-07-16 — film-base sampling and the cast experiments REMOVED

The 2026-07-15 "Ported" entry for 77c8113-adjacent film-base sampling is superseded: Sample Film Base was removed after its trial, together with the three patent-derived cast experiments built 2026-07-16 (saturation- weighted colour metering, tempered cast removal, roll balance — see PLAN-cast-experiments.md at 2b73c5d for the mechanisms). All were default-off and parity-clean; all verified mechanically correct end to end.

Why removed: the trial standard was "visibly better on real rolls", and none met it. On neutral-rich frames every method converges with the existing statistical estimate BY DESIGN (film-base agreed within 0.02D; weighted metering moved bounds ~0.01D; tempered cast at shipping constants shifts pixels ~1/7 of an 8-bit step). The existing two-axis bounds + confidence- gated neutral axis already handle these rolls well; the added UI surface wasn't paying for itself. Direction judged wrong by the user 2026-07-16.

Do not re-propose without new evidence — specifically, a real roll where casts visibly fail (dominant color, no neutrals, no usable rebate). If that roll appears, the removed work is complete and recoverable: fed271a (film-base sampling), fa3e095 (weighted metering), 36ae788 (tempered cast), 420f583 (roll balance), 2b73c5d (plan) — local-only commits, never pushed, reachable via reflog until gc.

Kept: the NegPy 0.38 constants port (1c1c3cb, this entry's parent), the spot densitometer / zone strip / negative character (shipped earlier and in regular use), and the research findings in the 2026-07-16 conversation. The densitometer remains the darkroom read-out surface; sidecars and the one roll-profile dotfile were scrubbed of the removed features' keys.