Merge dev: engrave window bar numbers and LilyPond fixes

A system can now be given the measure it starts at, in a First bar field
beside key and time. Per slice, since it is the one thing about a
replacement that cannot be inherited from the song. Bar numbering is a
Score property, so it is set once on the first staff, and made visible
only at a line beginning — that vector is fussy: #(#f #t #t) also prints
a number mid-system and #(#f #t #f) prints the second bar's rather than
the first's. It travels in the bundle's engraving object as `bar`.

Two things LilyPond 2.24 was quietly refusing to draw:

`\bar ":|"` and the other old repeat names produce nothing at all — no
error, no warning, exit status 0, just a missing repeat that you find on
the tablet. Every book and forum answer still uses them, so translate
them to the modern spellings.

`\clef treble_8` unquoted is not an octavated clef either. It parses as a
plain treble plus a stray "8" markup that lands under the first note, and
the staff then reads an octave off — a tenor line engraved at soprano
pitch. Quote it.

The source pane, which is where either of those would have been visible,
is now a collapsed section at the bottom rather than a permanent slab. It
uses the panel's own disclosure helper, lifted out of Editor so both can
call it.

README.md

@@ -8,7 +8,8 @@ A slice is one *system* — one full line of music across all voices, typically
 scroll, so the slicer's job is to cut a printed page into systems, clean them up
 enough to read on a tablet, and tag them with the score's navigation symbols.
 
-**Status: design only.** No code yet. The design is settled; see below.
+**New here? [docs/guide.md](docs/guide.md) walks you through making your first
+bundle.**
 
 ## How it works
 
@@ -29,22 +30,28 @@ at it.
 
 ## Installation
 
-Not yet installable. When it is:
-
 ```
 uv tool install --editable .
 ```
 
 That puts a `noteman-slicer` command on PATH which runs from any directory — no venv to
 activate. Dependencies (PyMuPDF, PySide6, OpenCV, numpy) are all wheels; nothing
-needs a system package.
+needs a system package. LilyPond is optional and only enables re-engraving.
+
+Then:
+
+```
+noteman-slicer edit my-song.pdf
+```
 
 ## Documentation
 
 | | |
 |---|---|
+| [docs/guide.md](docs/guide.md) | How to use it: install, cut a score, place markers, export a bundle. Start here if you just want to make one. |
 | [CONTEXT.md](CONTEXT.md) | Glossary. What a slice, cut, discard, bundle and song scale actually mean here. Start here. |
 | [docs/spec.md](docs/spec.md) | The specification: pipeline, geometry model, detection, editor, bundle format, and what noteman has to change. |
+| [docs/bundle-format.md](docs/bundle-format.md) | The Score Bundle Format — a standalone specification of the export format, independent of this tool. |
 
 Deferred work is tracked as issues and milestones on the Gitea repo, not in this
 tree.

docs/bundle-format.md

@@ -0,0 +1,366 @@
+# Score Bundle Format, version 1
+
+A container for one musical score, prepared for continuous-scroll display.
+
+A bundle holds the score as a sequence of images — one per system of music —
+together with the metadata that names the piece and the markers that describe
+how a performer navigates it. It is self-contained: nothing outside the file is
+needed to present the score.
+
+This document defines the format. It does not describe any particular program
+that writes or reads one.
+
+## Terminology
+
+**Slice** — one *system* of music: a single line spanning all voices, typically
+four to twelve bars, with lyrics intact. A slice is the atomic unit of the
+format. A slice is presented as an image; a slice that was engraved rather than
+scanned may also carry the notation it was engraved from.
+
+**Marker** — a semantic annotation attached to a slice, describing a navigational
+feature printed in the score: a rehearsal letter, a repeat, a jump.
+
+**Producer** — anything that writes a bundle. **Consumer** — anything that reads
+one.
+
+## Container
+
+A bundle is a ZIP archive.
+
+```
+<name>.zip
+├── song.json      manifest: metadata, slice order, markers
+├── original.pdf   the source document (optional)
+├── 001.webp
+├── 002.webp
+└── …              one file per slice
+```
+
+- `song.json` is required and must be at the archive root.
+- Slice images are at the archive root. Their names are given in `song.json`;
+  the zero-padded numbering shown is conventional, not required.
+- `original.pdf` is optional. When present it is the document the score was
+  prepared from, carried along for printing or archival. It is not required to
+  present the score and consumers may ignore it.
+- No directories, and no entries beyond those referenced by the manifest plus
+  the optional PDF.
+- Compression method is unconstrained. Producers typically deflate `song.json`
+  and store the images and PDF, which are already compressed.
+
+For scale: a twelve-page, twenty-four-slice choral score runs about 2.4 MB, of
+which roughly 830 KB is the source PDF and the rest slice images at ~20 KB each.
+
+## Manifest
+
+`song.json` is UTF-8 encoded JSON.
+
+```json
+{
+  "v": 1,
+  "title": "Ketun joululaulu",
+  "composer": "trad.",
+  "arranger": "P. Rapi",
+  "tempo": 92,
+  "slices": [
+    {
+      "file": "001.webp",
+      "markers": [
+        { "type": "rehearsal_letter", "label": "A" }
+      ]
+    },
+    {
+      "file": "002.webp",
+      "markers": [
+        { "type": "segno" },
+        { "type": "to_coda", "destination": 7 }
+      ]
+    },
+    { "file": "003.webp" }
+  ]
+}
+```
+
+### Top-level fields
+
+| Field | Type | | |
+|---|---|---|---|
+| `v` | integer | required | Format version. `1` for this document. |
+| `slices` | array | required | Ordered, at least one entry. See below. |
+| `title` | string | required | The name of the piece. |
+| `subtitle` | string | optional | Alternate or translated title. |
+| `composer` | string | optional | Who wrote the music. |
+| `original_artist` | string | optional | Who originally performed the work, where that differs from the composer. |
+| `arranger` | string | optional | Who adapted it for these forces. |
+| `lyricist` | string | optional | Who wrote the words. |
+| `translator` | string | optional | Who translated the words. |
+| `tempo` | integer | optional | Beats per minute. |
+| `voices` | string | optional | The parts in this arrangement, as free text. |
+
+**Optional fields are omitted when they have no value.** A consumer will not
+encounter an empty string or a null in place of an absent field.
+
+`tempo` is a number, never a word: a figure can drive a metronome or a click
+track, and verbal markings are not interchangeable between readers.
+
+Unrecognised top-level fields may be added by future versions. A consumer should
+ignore fields it does not know rather than reject the bundle.
+
+### Slices
+
+Each entry of `slices` is an object:
+
+| Field | Type | | |
+|---|---|---|---|
+| `file` | string | required | Name of the image entry in the archive. |
+| `markers` | array | optional | Markers on this slice. Omitted when there are none. |
+| `engraving` | object | optional | The notation this slice's image was engraved from, when it was engraved rather than scanned. See [Engraving](#engraving). |
+
+**The array order is the reading order of the score.** It is the only ordering
+the format defines. Filenames often sort into the same order, but a consumer
+must not derive order from them.
+
+A slice's **index** is its zero-based position in this array. Indices are the
+only identifiers the format has, and they are meaningful only within one bundle.
+
+## Slice images
+
+Every slice image in a bundle satisfies the following. A consumer can rely on
+these and does not need to inspect the images to lay them out.
+
+- **Format: WebP, losslessly encoded.** (Lossless rather than lossy because
+  engraved music is line art — large flat areas separated by thin high-contrast
+  strokes — which lossless encoders compress *better* than lossy ones as well as
+  exactly.)
+- **RGBA, with all three colour channels zero.** The image is carried entirely
+  by the alpha channel: ink is opaque black, paper is fully transparent, and
+  antialiased edges are partially transparent. Compositing a slice over a
+  background of any colour reproduces the printed appearance on that colour of
+  paper.
+- **Uniform width within a bundle.** Every slice has the same pixel width, so a
+  consumer can lay them out in a single column without measuring. Systems
+  shorter than the widest are padded on the right with transparent pixels; they
+  end early rather than stretching.
+- **Width is at most 1920 pixels**, and is frequently less. A narrower bundle is
+  not a defect: images are never enlarged beyond the resolution of their source,
+  because that adds bytes and softness without adding detail. Consumers should
+  scale to fit their own layout and should not treat 1920 as a target.
+- **Height varies per slice**, being the height of that system.
+- **Slices need not be rectangular in content.** Where two systems interleave —
+  for example a section label printed level with the previous system's lyric
+  line — the boundary between them steps, and each slice is delivered as its
+  bounding box with the region belonging to its neighbour left transparent. This
+  requires nothing special from a consumer; it composites correctly.
+
+Images are **presentation-ready**. They have already been deskewed, cropped,
+levelled and scaled as a set. Re-encoding, re-cropping or re-scaling them
+individually will at best waste work and at worst break the uniformity the
+format guarantees.
+
+One specific hazard is worth naming, because it is silent: an image pipeline
+that *discards* the alpha channel rather than compositing it will turn every
+slice into a solid black rectangle, since the colour channels are all zero.
+
+## Engraving
+
+Most slices are photographs of print: an image and nothing more. A slice that
+was *engraved* — set from notation rather than scanned — can carry the notation
+it came from, in an `engraving` object.
+
+```json
+{
+  "file": "007.webp",
+  "engraving": {
+    "lang": "lilypond",
+    "key": "aes",
+    "time": "4/4",
+    "print_time": false,
+    "bar": 33,
+    "voices": [
+      { "clef": "treble",   "notes": "c4 des ees f | ees2. r4", "lyrics": "Kai -- paa -- va sy -- dän" },
+      { "clef": "treble_8", "notes": "aes,4 aes aes aes | aes2. r4" },
+      { "clef": "bass",     "notes": "aes,4 ges f ees | aes2. r4" }
+    ]
+  }
+}
+```
+
+| Field | Type | | |
+|---|---|---|---|
+| `lang` | string | required | The notation language. `"lilypond"` is the only value defined by this version. |
+| `voices` | array | required | One entry per staff, in the order they are printed top to bottom. At least one. |
+| `key` | string | optional | Key signature, in `lang`'s spelling. For `lilypond`, the tonic of the major spelling: `"aes"`, `"c"`, `"fis"`. |
+| `time` | string | optional | Time signature, as `"4/4"`. |
+| `print_time` | boolean | optional | Whether the time signature is printed on this system. Default `false`. |
+| `bar` | integer | optional | The measure this system starts at, as printed above its first bar. Omitted when the system is not numbered. |
+
+Each entry of `voices`:
+
+| Field | Type | | |
+|---|---|---|---|
+| `notes` | string | required | The music for this staff, verbatim in `lang`. |
+| `clef` | string | optional | `"treble"`, `"treble_8"`, `"alto"`, `"bass"`. Default `"treble"`. |
+| `lyrics` | string | optional | The words under this staff, verbatim in `lang`. Omitted when the staff has none. |
+
+Three properties make this worth carrying:
+
+- **It is the source, not a transcription.** The image was engraved from exactly
+  these strings. A consumer that re-engraves them gets the same system back.
+- **It is editable.** A wrong note can be corrected here and the slice engraved
+  again, which a raster image does not allow.
+- **It is playable.** `voices` are separated per staff with pitches, durations
+  and a key, so the passage can be sounded — a practice track, a click, a
+  pitch reference — without anyone reading the image.
+
+`notes` and `lyrics` are opaque to this format. They are whatever `lang` accepts,
+including constructs the fields above say nothing about: slurs, dynamics,
+tuplets, and the tie idioms that carry a note across a slice boundary. A consumer
+that does not speak `lang` must pass them through unaltered or ignore them, never
+attempt to repair them.
+
+An `engraving` **describes the slice above it, not the whole song**. Each is
+self-contained: `key` and `time` are stated per slice, so nothing has to be
+inherited from a neighbour or from the bundle. Slices without an `engraving` are
+scanned, and the two kinds mix freely within one score — re-engraving a single
+ruined system is the ordinary case.
+
+A consumer that only presents the score can ignore `engraving` entirely. The
+image is always the authority on what the slice looks like; where an image and
+its engraving disagree, the image is what the producer intended to be read.
+
+Notation languages other than `lilypond` may be added by future versions. A
+consumer should ignore an `engraving` whose `lang` it does not know, and present
+the slice image as it would any other.
+
+## Markers
+
+A marker annotates the slice it appears on.
+
+| Field | Type | | |
+|---|---|---|---|
+| `type` | string | required | One of the vocabulary below. |
+| `label` | string | optional | Free text. Meaningful for `rehearsal_letter`, `section_label` and `volta`. |
+| `destination` | integer | optional | Index into `slices`. Present on jump types. |
+
+A slice may carry several markers. Their order within the array is not
+significant.
+
+### Vocabulary
+
+Named positions — places a performer may be directed to:
+
+| `type` | Meaning |
+|---|---|
+| `rehearsal_letter` | A boxed letter or number printed above a system, used to say "from C". `label` holds it. |
+| `section_label` | A named section: INTRO, VERSE, CHORUS. `label` holds the name. |
+| `segno` | The 𝄋 sign, target of a *dal segno*. |
+| `coda` | The 𝄌 sign, beginning of the closing section. |
+| `fine` | The end of the piece when reached by a *da capo* or *dal segno*. |
+
+Structural notation — printed context, affecting how the music is read but not
+directing the reader elsewhere:
+
+| `type` | Meaning |
+|---|---|
+| `repeat_start` | The start of a repeated passage. |
+| `repeat_end` | The end of a repeated passage. |
+| `volta` | An alternative ending bracket. `label` holds its number. |
+
+Jumps — points where the reader is directed to another slice:
+
+| `type` | Meaning |
+|---|---|
+| `to_coda` | "To Coda": leave here for the coda. |
+| `ds_al_coda` | *Dal segno al coda*: return to the segno. |
+| `ds_al_fine` | *Dal segno al fine*: return to the segno and play to the fine. |
+| `dc_al_coda` | *Da capo al coda*: return to the beginning. |
+| `dc_al_fine` | *Da capo al fine*: return to the beginning and play to the fine. |
+| `generic_jump` | An unclassified jump. |
+
+**Every jump marker states its destination explicitly**, as an index into
+`slices`. A consumer does not need to infer where a jump leads by searching for
+a matching `coda` or `segno`, and must not assume a bundle contains only one of
+each. A `destination` always refers to an existing index.
+
+Unrecognised marker types may be added by future versions. A consumer should
+ignore markers it does not understand rather than reject the bundle.
+
+## Versioning
+
+`v` is an integer that increases when a change would break an existing consumer.
+Additions that a consumer can safely ignore — new optional fields, new marker
+types, new `engraving` languages — do not increase it. `engraving` was added
+this way: a bundle carrying one is still a version 1 bundle, and a consumer that
+has never heard of it presents the score unchanged.
+
+A consumer should refuse a bundle whose `v` it does not recognise rather than
+attempt to interpret it.
+
+## Validating a bundle
+
+A consumer is advised to check:
+
+- `v` is a recognised version.
+- `title` is present and non-empty; `slices` is a non-empty array.
+- Every `file` names an entry present in the archive.
+- Every `destination` is within the bounds of `slices`.
+- Every `engraving` has a `lang` and a non-empty `voices`; unknown `lang` values
+  are ignored rather than rejected.
+- Archive entry names contain no path separators, no `..`, and no absolute
+  paths, as with any archive from an untrusted source.
+
+## Identity and updates
+
+A bundle describes one complete score. The format has no notion of updating a
+previously read bundle: there are no stable identifiers, and a slice's index is
+meaningful only within the bundle that contains it.
+
+Two bundles of the same piece are therefore independent documents, not versions
+of one. A consumer that stores imported bundles and assigns its own identifiers
+should treat a second bundle as a new score rather than merging it into an
+existing one — jump destinations resolved against the first bundle's slices do
+not survive being repointed at a second bundle's.
+
+## Complete example
+
+A 24-slice bundle, abbreviated:
+
+```
+song.zip
+├── song.json      1.4 KB
+├── original.pdf   827 KB
+├── 001.webp        21 KB   1489 × 1058
+├── 002.webp        18 KB   1489 × 818
+├── …
+└── 024.webp        1489 px wide, like every other slice
+```
+
+```json
+{
+  "v": 1,
+  "title": "Ketun joululaulu",
+  "composer": "trad.",
+  "arranger": "P. Rapi",
+  "tempo": 92,
+  "slices": [
+    { "file": "001.webp", "markers": [ { "type": "rehearsal_letter", "label": "A" } ] },
+    { "file": "002.webp", "markers": [ { "type": "segno" },
+                                       { "type": "to_coda", "destination": 7 } ] },
+    { "file": "003.webp" },
+    { "file": "004.webp" },
+    { "file": "005.webp" },
+    { "file": "006.webp" },
+    { "file": "007.webp", "engraving": { "lang": "lilypond", "key": "aes", "time": "4/4",
+                                         "voices": [ { "clef": "treble",
+                                                       "notes": "c4 des ees f | ees2. r4",
+                                                       "lyrics": "Kai -- paa -- va sy -- dän" },
+                                                     { "clef": "bass",
+                                                       "notes": "aes,4 ges f ees | aes2. r4" } ] } },
+    { "file": "008.webp", "markers": [ { "type": "coda" } ] },
+    { "file": "009.webp" }
+  ]
+}
+```
+
+Reading the score means presenting `001.webp` through `024.webp` in that order,
+in one column, each scaled to the same width. A reader who follows the `to_coda`
+on slice index 1 continues at slice index 7.

docs/guide.md

@@ -0,0 +1,147 @@
+# Making a bundle
+
+Start to finish: a score PDF in, one `.zip` out that noteman can open. Fifteen
+minutes for a typical four-page song, most of it spent nudging cuts.
+
+## Install
+
+```
+uv tool install --editable .
+```
+
+That puts `noteman-slicer` on PATH; it runs from any directory. Everything it
+needs is a wheel — no system packages. LilyPond is optional and only enables
+re-engraving (below); without it the tool works the same minus that pane.
+
+## The one command you need
+
+```
+noteman-slicer edit my-song.pdf
+```
+
+The editor opens on page 1 with detection's guesses already drawn: horizontal
+**cuts** between the systems, a **skew** correction, and a blue **content
+rectangle** marking what is music rather than page margin. All of it is a
+starting point — detection is an accelerator, not an authority. Fix whatever is
+wrong.
+
+Your work is saved to `my-song.slicer.json` next to the PDF, automatically on
+export and with Ctrl+S any time. Closing and reopening picks up where you left
+off.
+
+## What you do on each page
+
+1. **Straighten it.** If the staff lines slope, turn the *Skew* dial until they
+   are level. The preview updates live.
+2. **Fix the cuts.** One cut line per boundary between systems. Double-click to
+   add one, drag to move it, right-click to delete it. A cut is a polyline, not
+   a straight line — Ctrl-click on a cut adds a vertex, so it can bend around a
+   low-hanging lyric or a slur that crosses the gap. Right-click a vertex to
+   drop it.
+3. **Discard what isn't music.** Page headers, footers, page numbers and title
+   blocks are slices too, and they should not reach the tablet. Click the slice,
+   press <kbd>D</kbd>. Discarded slices show hatched. <kbd>D</kbd> again brings
+   one back.
+4. **Set the content rectangle.** Drag the blue edges so they hold the music and
+   nothing else. This is the horizontal crop for every slice on the page.
+5. **Check black and white points.** These arrive proposed from the scan, like
+   the cuts do. If the paper still shows texture, pull *White point* down; if the
+   notes look grey rather than solid, pull *Black point* up. Getting this wrong
+   is the one mistake you cannot see until the bundle is on the tablet — grey ink
+   becomes half-transparent ink, and nothing downstream can rescue it.
+
+Page Up / Page Down move between pages. Levels carry over from the previous
+page, so a consistent scan only needs setting once.
+
+## Markers
+
+Markers are the navigation symbols noteman uses to jump around the score:
+rehearsal letters, section labels, segno, coda, fine, repeats, voltas, and the
+D.S./D.C. instructions. They belong to a slice.
+
+Select the slice, pick the type, type a label if the type takes one (rehearsal
+letters, section labels and voltas do), and press **Add**.
+
+Jump markers — *to coda*, *D.S. al coda*, *D.C. al fine* and friends — also need
+a destination. After adding one, press **Set target…** and click the slice it
+jumps to, on any page. That is what lets noteman follow the repeat structure
+instead of just scrolling.
+
+## The title block
+
+Fill in the *Song* section. **Title is required** — export refuses without one.
+The rest (subtitle, composer, original artist, arranger, lyricist, translator,
+voices) is optional and travels with the bundle into noteman's library.
+
+*Tempo* is beats per minute, a number, because a number can drive a metronome
+and "Andante" cannot.
+
+## Export
+
+**Export bundle…**, choose where the `.zip` goes, done. It is named after the
+song's title — *Bicycle Race* becomes `Bicycle-Race.zip`. Inside are the slice
+images in order, their markers, the song metadata, and the original PDF as the
+archive copy. That zip is the whole interface to noteman; hand it over and open
+it there.
+
+Two things worth knowing:
+
+- **Shrink the original PDF…** offers to store the archived PDF as bilevel,
+  which is dramatically smaller for scans. It shows you a before/after crop
+  first — check that the staff lines survived. It never touches the slices.
+- **An exported project is spent.** Reopening the same PDF starts fresh from
+  detection rather than resuming decisions that already shipped. If you really
+  want the old cuts back, `noteman-slicer edit my-song.pdf --resume`.
+
+## Re-engraving a slice (optional, needs LilyPond)
+
+When a system is beyond rescue — a bad scan, a wrong transposition, a passage
+you want rewritten — shift-double-click it. A window opens where you enter the
+music as LilyPond, one block per voice, render, and compare against the
+original. Accept and the rendered version replaces that slice in the bundle.
+
+The LilyPond you typed travels in the bundle alongside the image, so the passage
+can be corrected and re-engraved later, or played, without the project file.
+
+## Mouse and keyboard
+
+| | |
+|---|---|
+| Double-click | add a cut |
+| Drag a cut | move it |
+| Ctrl-click a cut | add a vertex |
+| Right-click | delete the cut or vertex under the cursor |
+| Click a slice, then <kbd>D</kbd> | discard it (or bring it back) |
+| Drag the blue edges | resize the content rectangle |
+| Shift-double-click a slice | re-engrave it |
+| <kbd>Page Up</kbd> / <kbd>Page Down</kbd> | previous / next page |
+| <kbd>Ctrl</kbd>+<kbd>S</kbd> | save the project |
+
+## What the tool won't do
+
+Erasing a previous owner's pencil marks, chord letters and breath marks. Do that
+in GIMP before slicing — with a stylus it is quick, and no amount of thresholding
+substitutes for it.
+
+## When something looks wrong
+
+| | |
+|---|---|
+| Detection found no systems, or one giant one | The score has no bracket joining the staves; add the cuts by hand. |
+| "The PDF has changed since these cuts were made" | The file was edited or replaced under an existing project. The cuts probably no longer line up — re-cut. |
+| Export says a title is required | Fill in *Song → Title*. |
+| Slices look grey and washed out | The white point is too high. |
+| Notes have holes in them | The black point is too high. |
+
+## The command line
+
+The editor is the tool; these exist for checking things quickly.
+
+```
+noteman-slicer info my-song.pdf        # source type and page rasters
+noteman-slicer detect my-song.pdf      # detection results + debug overlays
+noteman-slicer project my-song.pdf     # what the project file currently holds
+noteman-slicer export my-song.pdf      # export without opening the editor
+```
+
+Every command takes `--type raster|vector` to override source-type detection.

docs/spec.md

@@ -236,6 +236,14 @@ point just under the paper's luminance and the paper vanishes completely; set th
 black point at the ink's darkest and notes go solid. It is also the single
 biggest lever on output size.
 
+**Detection proposes both**, like it proposes cuts and skew, because the default
+0–255 is the one setting whose harm is invisible until the bundle is on a tablet.
+Notation is two-tone, so Otsu's split between ink and paper is the measurement;
+the points sit halfway from it to each end of the range, leaving the ramp between
+them as the antialiasing. A page already scanned bilevel has no interior split —
+Otsu degenerates to 0 there — and is left at 0–255. The proposal is per page and
+the median becomes the song's, so a near-blank page cannot set it.
+
 Adaptive methods (CLAHE, adaptive thresholding) are the trap — tuned for text,
 they eat the thin stuff on notation: hairpin tips, slur ends, ledger lines,
 tapered beams. A global LUT whose effect you can see beats a local algorithm you
@@ -343,13 +351,19 @@ Otherwise: plain zip, no manifest beyond this, no checksums, hand-fixable.
 Python's `zipfile` is stdlib; the import side needs one zero-dep library
 (`fflate`), since Bun has zlib but no zip reader.
 
-**Contents:** slices, markers, the original PDF, and song-level text metadata
+**Contents:** slices, markers, the original PDF, and song-level metadata (title,
-(title, subtitle, composer, original artist, arranger, lyricist, translator,
+subtitle, composer, original artist, arranger, lyricist, translator, tempo,
 voice list). Metadata is included not because the slicer transforms it but
 because you have to read the title block anyway to mark the header slice
-discarded — typing eight fields while it's on screen beats reopening the PDF
+discarded — typing the fields while it's on screen beats reopening the PDF
 later.
 
+**Title is required**; everything else is optional and omitted when blank.
+**Tempo is an integer**, beats per minute — a number can drive a metronome and
+a starting-chord playback where *Andante* cannot, and two people will not agree
+what *Andante* means. noteman's column is currently free-form text and needs
+changing; see [`bundle-format.md`](bundle-format.md).
+
 Rehearsal MIDI and MP3s are deliberately out of the first bundle.
 
 ### One rule for the import side

noteman_slicer/bundle.py

@@ -13,6 +13,7 @@ a jump source's `destination`.
 from __future__ import annotations
 
 import json
+import re
 import zipfile
 from pathlib import Path
 
@@ -29,18 +30,66 @@ METADATA_FIELDS = (
     "arranger",
     "lyricist",
     "translator",
-    # Free-form, matching noteman's own column: scores notate tempo as a mix of
-    # BPM ("♩=72"), Italian ("Andante") and prose.
     "tempo",
     "voices",
 )
 
+# Beats per minute, exported as a JSON number. A figure is worth more than a
+# word here: "Andante" cannot drive a metronome and two people will not agree
+# what it means.
+NUMERIC_FIELDS = frozenset({"tempo"})
+
+
+def filename(project: Project) -> str:
+    """The bundle's name, from the song's title.
+
+    Spaces become dashes and anything that is not a letter, digit, dash, dot or
+    underscore goes. Letters keep their accents — ä and ö are not a filesystem's
+    problem — but a leading dot would make the bundle invisible.
+    """
+    # Drop the unsafe characters before collapsing whitespace, not after, or
+    # "Sävel & Ääni" keeps the dash the ampersand left behind.
+    title = re.sub(r"[^\w\s.-]", "", (project.metadata.get("title") or ""))
+    return f"{re.sub(r'\s+', '-', title.strip()).lstrip('.-') or 'song'}.zip"
+
+
+def _engraving(project: Project, page: int, slot: int) -> dict | None:
+    """The notation behind a re-engraved slice, or None for a scanned one.
+
+    The slice image stays the presentation; this is the notation it was made
+    from, carried so the music can be edited again or turned into sound. Key
+    and time are resolved against the song defaults here — a consumer reading
+    one slice should not have to know what the rest of the song inherited.
+    """
+    replacement = project.pages[page].replacements[slot]
+    if not replacement or not replacement.voices:
+        return None
+    return {
+        "lang": "lilypond",
+        "key": replacement.key or project.key,
+        "time": replacement.time or project.time,
+        "print_time": replacement.print_time,
+        **({"bar": replacement.bar} if replacement.bar else {}),
+        "voices": [
+            {"clef": v.clef, "notes": v.notes.strip()}
+            | ({"lyrics": v.lyrics.strip()} if v.lyrics.strip() else {})
+            for v in replacement.voices
+        ],
+    }
+
 
 def song_json(project: Project, files: list[str]) -> dict:
     payload: dict = {"v": FORMAT_VERSION}
     for field in METADATA_FIELDS:
-        value = project.metadata.get(field)
+        value = (project.metadata.get(field) or "").strip()
-        if value:
+        if not value:
+            continue
+        if field in NUMERIC_FIELDS:
+            try:
+                payload[field] = int(value)
+            except ValueError:
+                continue  # not a number, so not worth exporting as one
+        else:
             payload[field] = value
 
     kept = project.kept_slices()
@@ -52,6 +101,9 @@ def song_json(project: Project, files: list[str]) -> dict:
     slices: list[dict] = []
     for name, (page, slot) in zip(files, kept):
         entry: dict = {"file": name}
+        engraving = _engraving(project, page, slot)
+        if engraving:
+            entry["engraving"] = engraving
         markers = []
         for marker in project.pages[page].markers[slot]:
             item: dict = {"type": marker.type}
@@ -100,7 +152,15 @@ def write(project: Project, source: Source, path: Path) -> Path:
             zipfile.ZIP_DEFLATED,
         )
         if project.source.exists():
-            zf.write(project.source, "original.pdf")
+            pdf = project.source.read_bytes()
+            if project.optimise_pdf:
+                import pymupdf
+
+                from .pdfopt import optimise
+
+                shrunk, _ = optimise(pymupdf.open(project.source), len(pdf))
+                pdf = shrunk or pdf  # empty means it found no saving
+            zf.writestr("original.pdf", pdf, zipfile.ZIP_STORED)
         for name, data in zip(names, images):
             zf.writestr(name, data, zipfile.ZIP_STORED)
 

noteman_slicer/cli.py

@@ -87,7 +87,7 @@ def _export(args: argparse.Namespace) -> int:
     elif project.source_changed():
         print("WARNING: the PDF has changed since these cuts were made")
 
-    out = Path(args.out) if args.out else source.path.with_suffix(".zip")
+    out = Path(args.out) if args.out else source.path.with_name(bundle.filename(project))
     try:
         bundle.write(project, source, out)
     except ValueError as error:

noteman_slicer/detect.py

@@ -26,6 +26,7 @@ _SKEW_WORK_SCALE = 0.25
 _INK = 128  # below this is ink, above is paper
 _ANCHOR_KERNEL = 0.03  # vertical open kernel, as a fraction of page height
 _ANCHOR_MIN = 0.04  # a bracket is at least this tall, as a fraction of page
+_ANCHOR_MAX_RATIO = 2.0  # a stroke this much taller than the typical one is an artefact
 _PROFILE_FLOOR = 0.02  # ink-run threshold, as a fraction of the profile peak
 _EXPAND_REACH = 1.5  # how far past the bracket a system's ink reaches, in staff heights
 _STAFF_KERNEL = 0.05  # horizontal open kernel, as a fraction of page width
@@ -64,6 +65,7 @@ class PageDetection:
     systems: list[System] = field(default_factory=list)
     cuts: list[int] = field(default_factory=list)
     content: tuple[float, float, float, float] = (0.0, 0.0, 1.0, 1.0)
+    levels: tuple[int, int] = (0, 255)
 
     @property
     def bracketless(self) -> bool:
@@ -123,6 +125,17 @@ def system_anchors(gray: np.ndarray) -> list[Anchor]:
         if stats[i, cv2.CC_STAT_HEIGHT] > h * _ANCHOR_MIN
     ]
 
+    # A scanner leaves a dark line down the sheet edge — the binder shadow, the
+    # glass, the page next to it — and it runs the whole height of the scan.
+    # Being the tallest stroke on the page it wins every overlap below and
+    # swallows every system into one. A page's brackets and barlines are all
+    # about one system tall, so anything wildly taller than the typical stroke
+    # is not notation. Relative, not an absolute fraction of the page: a page
+    # holding one big system is legitimate and must survive.
+    if len(tall) > 1:
+        limit = float(np.median([a.bottom - a.top for a in tall])) * _ANCHOR_MAX_RATIO
+        tall = [a for a in tall if a.bottom - a.top <= limit] or tall
+
     # Tallest first, keeping only strokes that don't overlap one already kept:
     # a system's barlines all overlap its bracket, so each system yields one.
     # The kept stroke is the tallest, which is the bracket rather than a barline.
@@ -280,6 +293,26 @@ def staff_height(gray: np.ndarray, top: int, bottom: int) -> float | None:
     return float(np.median(intra) * 4)  # 5 lines, 4 spaces
 
 
+def ink_levels(gray: np.ndarray) -> tuple[int, int]:
+    """Black and white points that put the ink on black and the paper on white.
+
+    Left at 0–255 a slice ships whatever grey the scanner produced, and the
+    downscale to the song's width then blends every stroke edge further, so a
+    fine engraving arrives on the tablet as a wash. Notation is two-tone by
+    nature — ink and paper, nothing in between — so Otsu's split is exactly the
+    measurement wanted, and the points sit halfway to each end of the range from
+    it. Halfway rather than at the split itself: the ramp between them is the
+    antialiasing, and collapsing it would leave the notes jagged.
+    """
+    split = float(cv2.threshold(gray, 0, 255, cv2.THRESH_BINARY + cv2.THRESH_OTSU)[0])
+    if split < 1:
+        # A page already scanned bilevel has no interior split to find, and
+        # Otsu degenerates to 0. There is nothing between ink and paper to
+        # stretch, so leave the sliders where they are.
+        return 0, 255
+    return int(split / 2), int(split + (255 - split) / 2)
+
+
 def _gap(run: tuple[int, int], anchor: Anchor) -> int:
     """Vertical distance between an ink run and a bracket; 0 if they overlap."""
     start, end = run
@@ -375,5 +408,9 @@ def detect_page(gray: np.ndarray, skew: float | None = None) -> PageDetection:
     # would risk clipping a tempo mark or a section label above the first staff.
     left, right = content_columns(straight, anchors)
     return PageDetection(
-        skew=angle, systems=systems, cuts=cuts, content=(left, 0.0, right, 1.0)
+        skew=angle,
+        systems=systems,
+        cuts=cuts,
+        content=(left, 0.0, right, 1.0),
+        levels=ink_levels(straight),
     )

noteman_slicer/editor.py

@@ -19,6 +19,7 @@ from PySide6.QtGui import (
     QBrush,
     QColor,
     QImage,
+    QIntValidator,
     QKeySequence,
     QPainter,
     QPen,
@@ -33,6 +34,7 @@ from PySide6.QtWidgets import (
     QGraphicsScene,
     QGraphicsView,
     QComboBox,
+    QDialog,
     QHBoxLayout,
     QLabel,
     QLineEdit,
@@ -50,7 +52,7 @@ from PySide6.QtWidgets import (
 )
 
 from . import bundle, lilypond
-from .bundle import METADATA_FIELDS
+from .bundle import METADATA_FIELDS, NUMERIC_FIELDS
 from .detect import deskew, detect_page
 from .pdf import Source, open_source, page_raster
 from .project import (
@@ -73,6 +75,8 @@ _CUT = QColor(220, 40, 40)
 _CUT_ACTIVE = QColor(255, 120, 0)
 _VERTEX = QColor(255, 200, 0)
 _DISCARD = QColor(120, 120, 140, 90)
+_SELECT = QColor(0, 170, 0)
+_SELECT_WASH = QColor(0, 200, 60, 40)
 _RECT = QColor(40, 140, 220)
 _MARKER = QColor(150, 60, 190)
 _ENGRAVED = QColor(200, 120, 0)
@@ -80,6 +84,49 @@ _ENGRAVED_WASH = QColor(230, 160, 30, 55)
 _BADGE_Z = 10
 
 
+def section(title: str, box: QVBoxLayout, *, expanded: bool = True) -> QVBoxLayout:
+    """A collapsible section. Returns the layout its contents go into.
+
+    A disclosure arrow, not a checkable QGroupBox: a checkbox in a group
+    header reads as "enable this feature" rather than "expand this", and a
+    column of framed boxes with checkboxes is hard to scan.
+    """
+    header = QToolButton()
+    header.setText(title)
+    header.setCheckable(True)
+    header.setChecked(expanded)
+    header.setArrowType(Qt.DownArrow if expanded else Qt.RightArrow)
+    header.setToolButtonStyle(Qt.ToolButtonTextBesideIcon)
+    header.setAutoRaise(True)
+    header.setSizePolicy(QSizePolicy.Expanding, QSizePolicy.Fixed)
+    # Bold and greyed: a mid grey reads as a heading against both light and
+    # dark palettes without needing a second stylesheet.
+    header.setStyleSheet(
+        "QToolButton {"
+        "  border: none;"
+        "  font-weight: 700;"
+        "  color: #808080;"
+        "  padding: 7px 0 4px 0;"
+        "  text-align: left;"
+        "}"
+        "QToolButton:hover { color: #a0a0a0; }"
+    )
+
+    body = QWidget()
+    layout = QVBoxLayout(body)
+    layout.setContentsMargins(10, 6, 0, 10)
+    body.setVisible(expanded)
+
+    def toggled(open_: bool) -> None:
+        body.setVisible(open_)
+        header.setArrowType(Qt.DownArrow if open_ else Qt.RightArrow)
+
+    header.toggled.connect(toggled)
+    box.addWidget(header)
+    box.addWidget(body)
+    return layout
+
+
 class PageView(QGraphicsView):
     """Pan, zoom, and direct manipulation of cuts and the content rectangle."""
 
@@ -102,6 +149,7 @@ class PageView(QGraphicsView):
         self.selected_slice = 0
         self.picking = False
         self._drag: tuple[str, int, int] | None = None
+        self._fitted = False
 
     # -- state ------------------------------------------------------------
 
@@ -135,10 +183,15 @@ class PageView(QGraphicsView):
                     self._slice_polygon(slot, w, h), QPen(Qt.NoPen), QBrush(_DISCARD)
                 )
 
-        # The selected slice, outlined so trim anomalies are visible.
+        # The selected slice. The outline alone is nearly invisible: its top and
-        pen = QPen(QColor(0, 170, 0), 2)
+        # bottom edges run under the cut lines drawn over them, leaving two thin
+        # verticals at the page margins. A wash says which slice is selected at
+        # a glance; the outline stays, because it is what shows trim anomalies.
+        selected = self._slice_polygon(self.selected_slice, w, h)
+        scene.addPolygon(selected, QPen(Qt.NoPen), QBrush(_SELECT_WASH))
+        pen = QPen(_SELECT, 3)
         pen.setCosmetic(True)
-        scene.addPolygon(self._slice_polygon(self.selected_slice, w, h), pen)
+        scene.addPolygon(selected, pen)
 
         x0, y0, x1, y1 = self.project.page_content_rect(self.page_index)
         pen = QPen(_RECT, 2, Qt.DashLine)
@@ -204,20 +257,6 @@ class PageView(QGraphicsView):
         text.setPos(x, y)
         return x + box.width() * scale + pad * 3
 
-        for i, cut in enumerate(self.page.cuts):
-            colour = _CUT_ACTIVE if i == self.selected_cut else _CUT
-            pen = QPen(colour, 2)
-            pen.setCosmetic(True)
-            points = [QPointF(x * w, y * h) for x, y in cut.points]
-            for a, b in zip(points, points[1:]):
-                scene.addLine(a.x(), a.y(), b.x(), b.y(), pen)
-            if i == self.selected_cut:
-                r = HIT * 1.5 / max(self.transform().m11(), 1e-6)
-                for p in points:
-                    scene.addEllipse(
-                        p.x() - r, p.y() - r, r * 2, r * 2, QPen(Qt.NoPen), QBrush(_VERTEX)
-                    )
-
     def _slice_polygon(self, slot: int, w: int, h: int) -> QPolygonF:
         above, below = self.page.bounds(slot)
         top = [(0.0, 0.0), (1.0, 0.0)] if above is None else above.points
@@ -373,6 +412,15 @@ class PageView(QGraphicsView):
         self.redraw()
         self.changed.emit()
 
+    def resizeEvent(self, event) -> None:
+        super().resizeEvent(event)
+        # The fit in show_page runs before the window has been laid out, when
+        # the viewport is still its default size, so the first page opens at
+        # some arbitrary zoom. Redo it once, when the real size arrives.
+        if not self._fitted and self.pixmap is not None:
+            self._fitted = True
+            self.fitInView(self.scene().sceneRect(), Qt.KeepAspectRatio)
+
     def wheelEvent(self, event) -> None:
         factor = 1.15 if event.angleDelta().y() > 0 else 1 / 1.15
         self.scale(factor, factor)
@@ -421,48 +469,6 @@ class Editor(QMainWindow):
 
     # -- ui ---------------------------------------------------------------
 
-    def _section(self, title: str, box: QVBoxLayout, *, expanded: bool = True) -> QVBoxLayout:
-        """A collapsible section. Returns the layout its contents go into.
-
-        A disclosure arrow, not a checkable QGroupBox: a checkbox in a group
-        header reads as "enable this feature" rather than "expand this", and a
-        column of framed boxes with checkboxes is hard to scan.
-        """
-        header = QToolButton()
-        header.setText(title)
-        header.setCheckable(True)
-        header.setChecked(expanded)
-        header.setArrowType(Qt.DownArrow if expanded else Qt.RightArrow)
-        header.setToolButtonStyle(Qt.ToolButtonTextBesideIcon)
-        header.setAutoRaise(True)
-        header.setSizePolicy(QSizePolicy.Expanding, QSizePolicy.Fixed)
-        # Bold and greyed: a mid grey reads as a heading against both light and
-        # dark palettes without needing a second stylesheet.
-        header.setStyleSheet(
-            "QToolButton {"
-            "  border: none;"
-            "  font-weight: 700;"
-            "  color: #808080;"
-            "  padding: 7px 0 4px 0;"
-            "  text-align: left;"
-            "}"
-            "QToolButton:hover { color: #a0a0a0; }"
-        )
-
-        body = QWidget()
-        layout = QVBoxLayout(body)
-        layout.setContentsMargins(10, 6, 0, 10)
-        body.setVisible(expanded)
-
-        def toggled(open_: bool) -> None:
-            body.setVisible(open_)
-            header.setArrowType(Qt.DownArrow if open_ else Qt.RightArrow)
-
-        header.toggled.connect(toggled)
-        box.addWidget(header)
-        box.addWidget(body)
-        return layout
-
     def _panel(self) -> QWidget:
         inner = QWidget()
         box = QVBoxLayout(inner)
@@ -481,7 +487,7 @@ class Editor(QMainWindow):
         nav.addWidget(nxt)
         box.addLayout(nav)
 
-        page_section = self._section("Page", box)
+        page_section = section("Page", box)
         form = QFormLayout()
         page_section.addLayout(form)
         self.skew = QDoubleSpinBox()
@@ -510,7 +516,7 @@ class Editor(QMainWindow):
         reset.clicked.connect(self._reset_rect)
         form.addRow(reset)
 
-        marker_layout = self._section("Markers on this slice", box)
+        marker_layout = section("Markers on this slice", box)
         self.marker_list = QListWidget()
         self.marker_list.setMaximumHeight(110)
         marker_layout.addWidget(self.marker_list)
@@ -543,7 +549,7 @@ class Editor(QMainWindow):
         # slices are never re-engraved, and it is the tallest block here.
         self.ly_status = None
         if lilypond.available():
-            ly_layout = self._section("Re-engrave this slice", box, expanded=False)
+            ly_layout = section("Re-engrave this slice", box, expanded=False)
             open_engrave = QPushButton("Open engrave window…")
             open_engrave.setToolTip("Or double-click the slice on the page")
             open_engrave.clicked.connect(self._open_engrave)
@@ -553,7 +559,7 @@ class Editor(QMainWindow):
             self.ly_status.setStyleSheet("color: #808080;")
             ly_layout.addWidget(self.ly_status)
 
-        meta_layout = self._section("Song", box)
+        meta_layout = section("Song", box)
         meta_form = QFormLayout()
         meta_layout.addLayout(meta_form)
         self.metadata: dict[str, QLineEdit] = {}
@@ -564,8 +570,19 @@ class Editor(QMainWindow):
             required = field == "title"
             if required:
                 edit.setPlaceholderText("required")
+            if field in NUMERIC_FIELDS:
+                # Beats per minute, and only that: a number can drive a
+                # metronome where "Andante" cannot.
+                edit.setValidator(QIntValidator(20, 400, edit))
+                edit.setPlaceholderText("BPM")
+                edit.setFixedWidth(90)
             meta_form.addRow(f"{field.replace('_', ' ').title()}{' *' if required else ''}", edit)
 
+        self.optimise = QPushButton("Shrink the original PDF…")
+        self.optimise.setToolTip("Convert scanned pages to bilevel in the archived PDF")
+        self.optimise.clicked.connect(self._optimise_pdf)
+        meta_layout.addWidget(self.optimise)
+
         self.summary = QLabel()
         self.summary.setWordWrap(True)
         box.addWidget(self.summary)
@@ -758,6 +775,67 @@ class Editor(QMainWindow):
         }
         self.autosave.start()
 
+    def _optimise_pdf(self) -> None:
+        """Offer to shrink the archived PDF, showing the result before agreeing.
+
+        A before/after crop rather than a checkbox: the failure this can produce
+        — broken staff lines on a coarse scan — is obvious at a glance and
+        invisible in a byte count.
+        """
+        import pymupdf
+
+        from .pdfopt import Report, optimise, preview
+
+        self.statusBar().showMessage("examining the PDF…")
+        QApplication.processEvents()
+        source = self.project.source
+        data, report = optimise(pymupdf.open(source), source.stat().st_size)
+        self.statusBar().clearMessage()
+
+        if not data:
+            QMessageBox.information(self, "Nothing to shrink", report.summary())
+            self.project.optimise_pdf = False
+            return
+
+        dialog = QDialog(self)
+        dialog.setWindowTitle("Shrink the original PDF")
+        layout = QVBoxLayout(dialog)
+        text = QLabel(report.summary() + "\n\nThe slices are unaffected — only the archived PDF.")
+        text.setWordWrap(True)
+        layout.addWidget(text)
+
+        crop = preview(pymupdf.open(source), pymupdf.open(stream=data, filetype="pdf"))
+        crop = np.ascontiguousarray(crop)
+        h, w, _ = crop.shape
+        image = QImage(crop.data, w, h, w * 3, QImage.Format_BGR888).copy()
+        label = QLabel()
+        label.setPixmap(QPixmap.fromImage(image))
+        area = QScrollArea()
+        area.setWidget(label)
+        area.setWidgetResizable(True)
+        area.setMinimumHeight(420)
+        layout.addWidget(area)
+        layout.addWidget(QLabel("Original above, shrunk below. Check the staff lines."))
+
+        buttons = QHBoxLayout()
+        use = QPushButton("Use the smaller PDF")
+        use.clicked.connect(dialog.accept)
+        keep = QPushButton("Keep the original")
+        keep.clicked.connect(dialog.reject)
+        buttons.addWidget(use)
+        buttons.addWidget(keep)
+        layout.addLayout(buttons)
+        dialog.resize(1100, 700)
+
+        self.project.optimise_pdf = dialog.exec() == QDialog.Accepted
+        self._touched()
+        self.statusBar().showMessage(
+            "the bundle will carry the shrunk PDF"
+            if self.project.optimise_pdf
+            else "the bundle will carry the original PDF",
+            4000,
+        )
+
     def _reset_rect(self) -> None:
         """Back to what detection proposed for this page.
 
@@ -784,7 +862,10 @@ class Editor(QMainWindow):
             self.metadata["title"].setFocus()
             return
         target, _ = QFileDialog.getSaveFileName(
-            self, "Export bundle", str(self.source.path.with_suffix(".zip")), "Bundle (*.zip)"
+            self,
+            "Export bundle",
+            str(self.source.path.with_name(bundle.filename(self.project))),
+            "Bundle (*.zip)",
         )
         if not target:
             return

noteman_slicer/engrave.py

@@ -14,7 +14,7 @@ from __future__ import annotations
 import cv2
 import numpy as np
 from PySide6.QtCore import Qt
-from PySide6.QtGui import QImage, QKeySequence, QPixmap, QShortcut
+from PySide6.QtGui import QImage, QIntValidator, QKeySequence, QPixmap, QShortcut
 from PySide6.QtWidgets import (
     QCheckBox,
     QComboBox,
@@ -33,6 +33,7 @@ from PySide6.QtWidgets import (
 
 from . import lilypond
 from .detect import staff_height
+from .editor import section
 from .project import Project, Replacement, Voice
 
 
@@ -180,6 +181,16 @@ class EngraveWindow(QDialog):
         self.print_time.toggled.connect(self._settings_changed)
         row.addWidget(self.print_time, 1)
         top.addRow("Time", row)
+
+        # Per slice, unlike key and time: which measure a system starts at is
+        # the one thing that changes with every slice and cannot be inherited.
+        self.bar = QLineEdit("" if self.replacement.bar is None else str(self.replacement.bar))
+        self.bar.setValidator(QIntValidator(1, 9999, self.bar))
+        self.bar.setFixedWidth(70)
+        self.bar.setPlaceholderText("none")
+        self.bar.setToolTip("Printed above the first bar, as a printed score numbers its systems")
+        self.bar.textChanged.connect(self._bar_changed)
+        top.addRow("First bar", self.bar)
         box.addLayout(top)
 
         voices_label = QLabel("Voices")
@@ -209,11 +220,15 @@ class EngraveWindow(QDialog):
         self.status.setWordWrap(True)
         box.addWidget(self.status)
 
+        # Collapsed: the source is what the form writes for you, so it is for
+        # checking what a field did, not for working in. Open it and it stays
+        # open for the life of the window.
+        raw = section("LilyPond source", box, expanded=False)
         self.generated = QPlainTextEdit()
         self.generated.setReadOnly(True)
-        self.generated.setMaximumHeight(120)
+        self.generated.setMaximumHeight(220)
         self.generated.setStyleSheet("color: #808080;")
-        box.addWidget(self.generated)
+        raw.addWidget(self.generated)
         self._refresh_source()
         return panel
 
@@ -240,6 +255,10 @@ class EngraveWindow(QDialog):
         row.setParent(None)
         self._refresh_source()
 
+    def _bar_changed(self, text: str) -> None:
+        self.replacement.bar = int(text) if text.strip().isdigit() else None
+        self._refresh_source()
+
     def _settings_changed(self) -> None:
         # Set on the song, not the slice: they are song properties in practice,
         # and this is what makes the next re-engraved slice open pre-filled.

noteman_slicer/lilypond.py

@@ -12,6 +12,7 @@ scaling.
 
 from __future__ import annotations
 
+import re
 import shutil
 import subprocess
 import tempfile
@@ -63,6 +64,25 @@ RELATIVE_REFERENCE = {
     "bass": "c",
 }
 
+# LilyPond renamed the repeat barlines and silently draws *nothing* for the old
+# names — no error, no warning, just a missing repeat that you find on the
+# tablet. Every book, every forum answer and every score anyone has typed before
+# uses the old ones, so translate them.
+_BAR_ALIASES = {
+    "|:": ".|:",
+    ":|": ":|.",
+    ":|:": ":|.|:",
+    "||:": ".|:",
+    ":||": ":|.",
+    ":||:": ":|.|:",
+}
+_BAR = re.compile(r'(\\bar\s*")([^"]*)(")')
+
+
+def _modernise_bars(notes: str) -> str:
+    return _BAR.sub(lambda m: m[1] + _BAR_ALIASES.get(m[2], m[2]) + m[3], notes)
+
+
 _PREAMBLE = """\\version "2.24.0"
 \\paper {
   indent = 0\\mm
@@ -85,17 +105,35 @@ def generate(replacement, key: str, time: str) -> str:
     key = replacement.key or key
     time = replacement.time or time
 
+    # Bar numbering is a Score property, so it is set once, on the first staff.
+    # Visible at the beginning of a line and nowhere else — which in a
+    # one-system slice means exactly one number, above the first bar, the way a
+    # printed score numbers its systems. The empty bar line is what gives the
+    # number a line beginning to attach to.
+    number = ""
+    if replacement.bar:
+        number = (
+            f"      \\set Score.currentBarNumber = #{int(replacement.bar)}\n"
+            "      \\override Score.BarNumber.break-visibility = #'#(#f #f #t)\n"
+            '      \\bar ""\n'
+        )
+
     staves = []
     for voice in replacement.voices:
         hide = "" if replacement.print_time else "      \\omit Staff.TimeSignature\n"
-        body = voice.notes.strip() or "s1"
+        body = _modernise_bars(voice.notes.strip()) or "s1"
         reference = RELATIVE_REFERENCE.get(voice.clef, "c'")
         staff = (
             "    \\new Staff {\n"
             f"{hide}"
-            f"      \\clef {voice.clef}\n"
+            # Quoted, because an octavated name has to be: unquoted,
+            # `\clef treble_8` parses as a plain treble clef with a stray "8"
+            # markup that lands under the first note, and the staff then reads
+            # an octave off.
+            f'      \\clef "{voice.clef}"\n'
             f"      \\key {key} \\major\n"
             f"      \\time {time}\n"
+            f"{number if not staves else ''}"
             f"      \\relative {reference} {{ {body} }}\n"
             "    }\n"
         )

noteman_slicer/pdf.py

@@ -90,13 +90,28 @@ def page_raster(source: Source, index: int) -> np.ndarray:
             # Pixmap(doc, xref) rather than decoding extract_image() bytes:
             # MuPDF handles JBIG2 and CCITT, which no image library will.
             pix = pymupdf.Pixmap(source.doc, xref)
-            return _to_gray(pix)
+            # The embedded image is in its own orientation, not the page's: a
+            # scanner that fed the sheet sideways stores it landscape and the
+            # PDF sets /Rotate so viewers turn it upright. Extracting by xref
+            # bypasses that, so apply it here — otherwise every system runs
+            # down the page and detection finds nothing.
+            return _rotate(_to_gray(pix), page.rotation)
         # A scanned PDF whose page has no embedded image (a blank, or a
         # cover typeset in vector). Rendering is the only option left.
 
     return _to_gray(page.get_pixmap(dpi=source.render_dpi, colorspace=pymupdf.csGRAY))
 
 
+def _rotate(gray: np.ndarray, degrees: int) -> np.ndarray:
+    """Turn a page raster clockwise by a multiple of 90°, as /Rotate means it.
+
+    ponytail: quarter turns only. A page rotated by anything else would need
+    resampling, and no scanner produces one.
+    """
+    turns = round(degrees / 90) % 4
+    return np.ascontiguousarray(np.rot90(gray, -turns)) if turns else gray
+
+
 def _to_gray(pix: pymupdf.Pixmap) -> np.ndarray:
     if pix.alpha or pix.colorspace is None or pix.colorspace.n != 1:
         pix = pymupdf.Pixmap(pymupdf.csGRAY, pix)

noteman_slicer/pdfopt.py

@@ -0,0 +1,172 @@
+"""Optional shrinking of the original PDF carried in a bundle.
+
+Scanned scores are usually black ink on white paper stored as 8-bit greyscale
+or RGB, which costs several times what the same page costs as a bilevel image.
+Converting them is worth 7–9× on a real corpus.
+
+Two things it must not do, both found by looking at output rather than at
+numbers:
+
+  * A page that is genuinely coloured — cover artwork — loses its artwork.
+  * A scan too coarse to have more than about one pixel per staff line comes
+    back with the staff lines broken.
+
+Both are detectable before converting, so both are skipped. Everything skipped
+is reported, so a caller can say what was left alone and why.
+
+This affects only the archival copy of the score. Slices are cut from the
+original before any of this and are unchanged either way.
+"""
+
+from __future__ import annotations
+
+from dataclasses import dataclass, field
+
+import cv2
+import numpy as np
+import pymupdf
+
+# Below this many pixels per inch as the image is *placed on the page*, staff
+# lines are about a pixel wide and thresholding breaks them. Measured against a
+# corpus where the one failure sat at ~115 DPI and the successes at 260+.
+MIN_DPI = 200
+
+# An image is "coloured" when this share of sampled pixels are off-grey by
+# more than _CHROMA. The two populations are far apart: measured on a corpus,
+# cover artwork sits at 44% while a greyscale scan's sensor tint reaches 3%.
+# Ten percent sits in the gap with room on both sides.
+_CHROMA = 24
+_COLOUR_SHARE = 0.10
+
+_BLOCK = 31  # adaptive threshold window
+_OFFSET = 15
+
+
+@dataclass
+class Report:
+    before: int = 0
+    after: int = 0
+    converted: int = 0
+    skipped: dict[str, int] = field(default_factory=dict)
+
+    @property
+    def ratio(self) -> float:
+        return self.after / self.before if self.before else 1.0
+
+    def skip(self, reason: str) -> None:
+        self.skipped[reason] = self.skipped.get(reason, 0) + 1
+
+    def summary(self) -> str:
+        if not self.converted:
+            return "nothing to optimise — every image is already bilevel, coloured or too coarse"
+        parts = [
+            f"{self.before / 1024:.0f} KB → {self.after / 1024:.0f} KB "
+            f"({self.ratio * 100:.0f}%), {self.converted} images converted"
+        ]
+        for reason, count in sorted(self.skipped.items()):
+            parts.append(f"{count} left alone: {reason}")
+        return "\n".join(parts)
+
+
+def _is_coloured(image: np.ndarray) -> bool:
+    if image.ndim != 3 or image.shape[2] < 3:
+        return False
+    sample = image[::4, ::4, :3].astype(np.int16)
+    spread = sample.max(axis=2) - sample.min(axis=2)
+    return float((spread > _CHROMA).mean()) > _COLOUR_SHARE
+
+
+def _placed_dpi(page: pymupdf.Page, item, width: int) -> float:
+    """Pixels per inch of an image as it appears on the page.
+
+    Not the pixel count: a page split into tiles has small images at a high
+    resolution, and a full-page image can be large yet coarse.
+    """
+    try:
+        bbox = pymupdf.Rect(page.get_image_bbox(item))
+    except (ValueError, RuntimeError):
+        return float("inf")
+    inches = abs(bbox.width) / 72.0
+    return width / inches if inches > 0 else float("inf")
+
+
+def optimise(doc: pymupdf.Document, source_bytes: int) -> tuple[bytes, Report]:
+    """Return the optimised PDF and a report of what was done.
+
+    `doc` is modified in place, so pass a copy or reopen afterwards.
+    """
+    report = Report(before=source_bytes)
+
+    for page in doc:
+        for item in page.get_images(full=True):
+            xref = item[0]
+            info = doc.extract_image(xref)
+
+            if info.get("bpc") == 1:
+                report.skip("already bilevel")
+                continue
+
+            if _placed_dpi(page, item, info["width"]) < MIN_DPI:
+                report.skip(f"below {MIN_DPI} DPI, staff lines would break")
+                continue
+
+            raw = cv2.imdecode(np.frombuffer(info["image"], np.uint8), cv2.IMREAD_UNCHANGED)
+            if raw is None:
+                report.skip("unreadable encoding")
+                continue
+
+            if _is_coloured(raw):
+                report.skip("coloured artwork")
+                continue
+
+            gray = cv2.cvtColor(raw, cv2.COLOR_BGR2GRAY) if raw.ndim == 3 else raw
+            bilevel = cv2.adaptiveThreshold(
+                gray, 255, cv2.ADAPTIVE_THRESH_MEAN_C, cv2.THRESH_BINARY, _BLOCK, _OFFSET
+            )
+            ok, buffer = cv2.imencode(".png", bilevel, [cv2.IMWRITE_PNG_COMPRESSION, 9])
+            if not ok:
+                report.skip("re-encoding failed")
+                continue
+            try:
+                page.replace_image(xref, stream=buffer.tobytes())
+            except (ValueError, RuntimeError):
+                report.skip("could not be replaced")
+                continue
+            report.converted += 1
+
+    data = doc.tobytes(garbage=4, deflate=True, clean=True)
+    # Never hand back something larger than what came in.
+    if len(data) >= source_bytes:
+        report.after = source_bytes
+        report.converted = 0
+        report.skip("no saving available")
+        return b"", report
+
+    report.after = len(data)
+    return data, report
+
+
+def preview(original: pymupdf.Document, optimised: pymupdf.Document, dpi: int = 260):
+    """A stacked before/after crop of the first page, for eyeballing the result.
+
+    The numbers cannot show the failure this guards against — a broken staff
+    line is obvious at a glance and invisible in a byte count.
+    """
+    rect = original[0].rect
+    clip = pymupdf.Rect(
+        rect.x0 + rect.width * 0.08,
+        rect.y0 + rect.height * 0.20,
+        rect.x0 + rect.width * 0.58,
+        rect.y0 + rect.height * 0.33,
+    )
+
+    def render(doc: pymupdf.Document) -> np.ndarray:
+        pix = doc[0].get_pixmap(dpi=dpi, clip=clip)
+        image = np.frombuffer(pix.samples, np.uint8).reshape(pix.height, pix.width, pix.n)
+        return image[:, :, :3] if pix.n >= 3 else cv2.cvtColor(image[:, :, 0], cv2.COLOR_GRAY2BGR)
+
+    before, after = render(original), render(optimised)
+    h = min(before.shape[0], after.shape[0])
+    w = min(before.shape[1], after.shape[1])
+    divider = np.full((4, w, 3), 128, np.uint8)
+    return np.vstack([before[:h, :w], divider, after[:h, :w]])

noteman_slicer/project.py

@@ -15,6 +15,7 @@ import hashlib
 import json
 from dataclasses import dataclass, field
 from pathlib import Path
+from statistics import median
 
 from .detect import PageDetection
 
@@ -146,6 +147,10 @@ class Replacement:
     voices: list[Voice] = field(default_factory=list)
     key: str | None = None
     time: str | None = None
+    # The measure this system starts at, printed above its first bar the way a
+    # score numbers its systems. Per slice and nothing else: it is the one thing
+    # about a replacement that cannot be inherited or guessed.
+    bar: int | None = None
     # The printed score repeats the key signature at every system but not the
     # time signature, so a re-engraved middle slice must not show one.
     print_time: bool = False
@@ -222,6 +227,10 @@ class Project:
     key: str = "c"
     time: str = "4/4"
     clefs: list[str] = field(default_factory=list)
+    # Shrink the archival PDF carried in the bundle by converting its scanned
+    # pages to bilevel. Off by default: it is lossy on the copy kept for
+    # printing, and on some scans it breaks staff lines.
+    optimise_pdf: bool = False
     path: Path | None = None
     # Set once the song has been exported. A project is spent at that point:
     # opening the PDF again starts a fresh session from detection rather than
@@ -292,7 +301,18 @@ class Project:
                     content_rect=detection.content,
                 )
             )
-        return cls(source=source, source_hash=hash_file(source), pages=pages)
+        # Levels per song, not per page: a scanner's contrast does not change
+        # between sheets, and one pair of sliders for the whole song is what a
+        # user actually wants to nudge. The median keeps a near-blank page —
+        # where the ink/paper split is guesswork — from setting them.
+        proposals = [d.levels for d in detections] or [(0, 255)]
+        levels = (
+            int(median(b for b, _ in proposals)),
+            int(median(w for _, w in proposals)),
+        )
+        return cls(
+            source=source, source_hash=hash_file(source), pages=pages, levels=levels
+        )
 
     def save(self, path: Path | None = None) -> Path:
         """Atomic write, so a crash mid-save cannot destroy the previous state."""
@@ -308,6 +328,7 @@ class Project:
             "key": self.key,
             "time": self.time,
             "clefs": self.clefs,
+            "optimise_pdf": self.optimise_pdf,
             "pages": [
                 {
                     "skew": page.skew,
@@ -339,6 +360,7 @@ class Project:
                             **({"key": r.key} if r.key else {}),
                             **({"time": r.time} if r.time else {}),
                             **({"print_time": True} if r.print_time else {}),
+                            **({"bar": r.bar} if r.bar else {}),
                         }
                         for r in page.replacements
                     ],
@@ -395,6 +417,7 @@ class Project:
                         key=r.get("key"),
                         time=r.get("time"),
                         print_time=r.get("print_time", False),
+                        bar=r.get("bar"),
                     )
                     for r in page.get("replacements", [None] * len(page["discards"]))
                 ],
@@ -415,6 +438,7 @@ class Project:
             key=data.get("key", "c"),
             time=data.get("time", "4/4"),
             clefs=data.get("clefs", []),
+            optimise_pdf=data.get("optimise_pdf", False),
         )
 
     def source_changed(self) -> bool:

noteman_slicer/render.py

@@ -26,7 +26,10 @@ from .project import Cut, Project
 
 MAX_WIDTH = 1920
 ALPHA_LEVELS = 16  # quantising alpha costs nothing visible and ~32% of the bytes
-_SPECK_AREA = 300  # ink blobs smaller than this don't anchor a trim
+# A row or column carrying less ink than this is a fleck, not content: at least
+# this many pixels, and at least this share of the slice's own size.
+_SPECK_INK = 8
+_SPECK_SHARE = 0.005
 
 
 @dataclass
@@ -105,26 +108,24 @@ def _ink_bbox(gray: np.ndarray) -> tuple[int, int, int, int] | None:
 
     One scan fleck at the far left would otherwise anchor the trim and shift
     that slice relative to every other one.
+
+    Measured per row and per column rather than per blob. Judging each blob on
+    its own area throws away a whole line of lyrics — every letter is its own
+    small component, and no single one is big enough to keep — which is how a
+    slice loses its bottom voice's words. A row carrying a line of text carries
+    plenty of ink *in total*, and a fleck's row carries almost none.
     """
-    ink = (gray < 200).astype(np.uint8)
+    ink = gray < 200
-    count, _, stats, _ = cv2.connectedComponentsWithStats(ink, 8)
+    rows, cols = ink.sum(axis=1), ink.sum(axis=0)
-    boxes = [
+    kept_rows = np.where(rows >= max(_SPECK_INK, ink.shape[1] * _SPECK_SHARE))[0]
-        (
+    kept_cols = np.where(cols >= max(_SPECK_INK, ink.shape[0] * _SPECK_SHARE))[0]
-            stats[i, cv2.CC_STAT_LEFT],
+    if not kept_rows.size or not kept_cols.size:
-            stats[i, cv2.CC_STAT_TOP],
-            stats[i, cv2.CC_STAT_LEFT] + stats[i, cv2.CC_STAT_WIDTH],
-            stats[i, cv2.CC_STAT_TOP] + stats[i, cv2.CC_STAT_HEIGHT],
-        )
-        for i in range(1, count)
-        if stats[i, cv2.CC_STAT_AREA] >= _SPECK_AREA
-    ]
-    if not boxes:
         return None
     return (
-        min(b[0] for b in boxes),
+        int(kept_cols[0]),
-        min(b[1] for b in boxes),
+        int(kept_rows[0]),
-        max(b[2] for b in boxes),
+        int(kept_cols[-1]) + 1,
-        max(b[3] for b in boxes),
+        int(kept_rows[-1]) + 1,
     )
 
 

tests/test_detect.py

@@ -14,7 +14,12 @@ import numpy as np
 
 sys.path.insert(0, str(Path(__file__).resolve().parents[1]))
 
-from noteman_slicer.detect import deskew, deskew_angle, detect_page  # noqa: E402
+from noteman_slicer.detect import (  # noqa: E402
+    deskew,
+    deskew_angle,
+    detect_page,
+    ink_levels,
+)
 
 W, H = 1000, 1400
 STAFF_GAP = 15  # → staff height 60, so expansion reaches 90px past a bracket
@@ -71,6 +76,23 @@ def main() -> int:
         found = deskew_angle(deskew(page, angle))
         assert abs(found + angle) <= 0.15, f"skew {angle}: got {found}"
 
+    # Levels are proposed too. A grey scan left at 0–255 ships its wash to the
+    # tablet, and the downscale to the song's width only blends it further.
+    grey = np.full((H, W), 210, np.uint8)  # paper, not white
+    grey[200:400, 100:900] = 70  # ink, not black
+    black, white = ink_levels(grey)
+    assert black < 70 < white < 210, (black, white)
+    # A page already bilevel has nothing between ink and paper to stretch.
+    assert ink_levels(_page()) == (0, 255)
+
+    # A scanner's edge line runs the whole height of the sheet. Being taller
+    # than every bracket it used to win each overlap and swallow the page into
+    # one system — Olukainen juomukainen, where five pages of six came out as a
+    # single slice each.
+    scanned = _page()
+    scanned[10 : H - 10, W - 8 : W - 4] = 0
+    assert len(detect_page(scanned).systems) == 2, "an edge artefact is not a bracket"
+
     # No brackets: every ink run is its own system.
     bare = np.full((H, W), 255, np.uint8)
     for y in (200, 500, 800):

tests/test_editor.py

@@ -19,6 +19,7 @@ sys.path.insert(0, str(Path(__file__).resolve().parents[1]))
 
 from PySide6.QtWidgets import QApplication  # noqa: E402
 
+from noteman_slicer import bundle  # noqa: E402
 from noteman_slicer.detect import detect_page  # noqa: E402
 from noteman_slicer.editor import Editor  # noqa: E402
 from noteman_slicer.pdf import open_source, page_raster  # noqa: E402
@@ -105,6 +106,28 @@ def main() -> int:
     assert reloaded.pages[0].levels == (40, 210)
     assert [c.points for c in reloaded.pages[0].cuts] == [c.points for c in page.cuts]
 
+    # The page fits the viewport once the window has a real size. show_page's
+    # own fit runs before layout, when the viewport is still its default.
+    editor.resize(900, 700)
+    editor.show()
+    app.processEvents()
+    scene = editor.view.sceneRect()
+    scale = editor.view.transform().m11()
+    viewport = editor.view.viewport()
+    fill = max(
+        scale * scene.width() / viewport.width(),
+        scale * scene.height() / viewport.height(),
+    )
+    # Fit means nearly touching one edge — Qt leaves a small margin of its own.
+    # A "≤ 1" check alone would pass a page zoomed down to a dot.
+    assert 0.9 <= fill <= 1.02, f"page is not fitted to the window: {fill:.3f}"
+
+    # The bundle is named after the song, not the PDF.
+    assert bundle.filename(project) == "Ketun-joululaulu.zip"
+    project.metadata["title"] = "AC/DC: T.N.T. (live)"
+    assert bundle.filename(project) == "ACDC-T.N.T.-live.zip"
+    project.metadata["title"] = "Ketun joululaulu"
+
     editor.close()
     source.close()
     for f in (pdf, saved):

tests/test_lilypond.py

@@ -52,6 +52,39 @@ def _scan_pdf(path: Path) -> None:
 
 
 def main() -> int:
+    # Bar aliases are string work, so they are checked whether or not LilyPond
+    # is installed. The old repeat names draw nothing at all in 2.24 — silently,
+    # which is how a missing repeat reaches a tablet.
+    aliased = lilypond.generate(
+        Replacement(voices=[Voice("treble", 'c4 d \\bar ":|" e f \\bar "|:" g', "")]), "c", "4/4"
+    )
+    assert '\\bar ":|."' in aliased and '\\bar ".|:"' in aliased, aliased
+    kept = lilypond.generate(
+        Replacement(voices=[Voice("treble", 'c4 \\bar "|." d', "")]), "c", "4/4"
+    )
+    assert '\\bar "|."' in kept, "a name LilyPond still knows is left alone"
+
+    # An octavated clef name must be quoted. Unquoted, `\clef treble_8` is a
+    # plain treble with a stray "8" markup under the first note, an octave off.
+    tenor = lilypond.generate(
+        Replacement(voices=[Voice("treble_8", "c4 d", "")]), "c", "4/4"
+    )
+    assert '\\clef "treble_8"' in tenor, tenor
+
+    # A bar number is set once, on the first staff, since it is a Score
+    # property, and is visible only at a line beginning — one number above the
+    # first bar, as a printed score numbers its systems.
+    numbered = lilypond.generate(
+        Replacement(voices=[Voice("treble", "c4 d", ""), Voice("bass", "c4 d", "")], bar=33),
+        "c",
+        "4/4",
+    )
+    assert numbered.count("currentBarNumber = #33") == 1, numbered
+    assert "break-visibility = #'#(#f #f #t)" in numbered
+    assert "currentBarNumber" not in lilypond.generate(
+        Replacement(voices=[Voice("treble", "c4 d", "")]), "c", "4/4"
+    ), "an unnumbered system prints no number"
+
     if not lilypond.available():
         print("ok (skipped: LilyPond not installed)")
         return 0
@@ -138,6 +171,7 @@ def main() -> int:
     assert page.replacements[second] is SATB
 
     # Round-trip, including the song-level engraving defaults.
+    SATB.bar = 33
     project.key, project.time, project.clefs = "aes", "3/4", ["treble", "bass"]
     saved = project.save()
     reloaded = Project.load(saved)
@@ -146,6 +180,7 @@ def main() -> int:
     assert restored is not None
     assert [v.clef for v in restored.voices] == ["treble", "bass"]
     assert restored.voices[0].lyrics == "la la la la la la"
+    assert restored.bar == 33, "the slice's bar number survives a save"
     assert reloaded.pages[0].replacements[first] is None
 
     source.close()

tests/test_markers.py

@@ -22,6 +22,8 @@ from noteman_slicer.project import (  # noqa: E402
     Cut,
     Marker,
     Project,
+    Replacement,
+    Voice,
     default_path,
 )
 
@@ -76,13 +78,45 @@ def main() -> int:
 
     # Export resolves (page, slot) to the slice's index in the bundle.
     names = [f"{i + 1:03}.webp" for i in range(len(project.kept_slices()))]
+    project.metadata.update({"title": "Test song", "tempo": "92", "composer": ""})
     payload = song_json(project, names)
+    # Tempo is a number, not a string; empty fields are absent, not "".
+    assert payload["tempo"] == 92, payload["tempo"]
+    assert "composer" not in payload
+
+    project.metadata["tempo"] = "Andante"
+    assert "tempo" not in song_json(project, names), "words are not a tempo"
+    project.metadata["tempo"] = "92"
     slices = payload["slices"]
     assert [s["file"] for s in slices] == names
     assert slices[0]["markers"][0] == {"type": "rehearsal_letter", "label": "A"}
     assert slices[1]["markers"][0] == {"type": "coda"}
     assert slices[0]["markers"][1] == {"type": "to_coda", "destination": 1}
 
+    # A re-engraved slice carries its notation into the bundle; a scanned one
+    # carries none. This is what makes a later edit or a MIDI render possible
+    # from the bundle alone.
+    project.key, project.time = "aes", "3/4"
+    page.replacements[second] = Replacement(
+        voices=[Voice("treble", "c4 d e f", "la la la la"), Voice("bass", " c4 d e f ", "  ")],
+        bar=33,
+    )
+    engraved = song_json(project, names)["slices"]
+    assert "engraving" not in engraved[0], "a scanned slice has no notation"
+    ly = engraved[1]["engraving"]
+    assert ly["lang"] == "lilypond"
+    # Song defaults are resolved per slice: reading one slice needs no context.
+    assert (ly["key"], ly["time"], ly["print_time"], ly["bar"]) == ("aes", "3/4", False, 33)
+    assert ly["voices"][0] == {"clef": "treble", "notes": "c4 d e f", "lyrics": "la la la la"}
+    assert "lyrics" not in ly["voices"][1], "an empty field is absent, not empty"
+    assert ly["voices"][1]["notes"] == "c4 d e f"
+
+    override = Replacement(voices=page.replacements[second].voices, key="d", print_time=True)
+    page.replacements[second] = override
+    ly = song_json(project, names)["slices"][1]["engraving"]
+    assert (ly["key"], ly["time"], ly["print_time"]) == ("d", "3/4", True)
+    page.replacements[second] = None
+
     # A jump whose target got discarded is dropped, not exported dangling.
     project.pages[0].discards[second] = True
     dropped = song_json(project, ["001.webp"])

tests/test_pdf.py

@@ -28,15 +28,21 @@ def _vector_pdf(path: Path, pages: int = 2) -> None:
     doc.save(path)
 
 
-def _scan_pdf(path: Path, pages: int = 2, w: int = 1653, h: int = 2332) -> None:
+def _scan_pdf(path: Path, pages: int = 2, w: int = 1653, h: int = 2332, rotation: int = 0) -> None:
-    """Each page is one full-page grayscale image — what a real scan looks like."""
+    """Each page is one full-page grayscale image — what a real scan looks like.
+
+    `rotation` reproduces a sheet fed sideways: the image is stored in its own
+    orientation and /Rotate turns it upright for a viewer.
+    """
     art = np.full((h, w), 255, np.uint8)
     art[500:505, 100 : w - 100] = 0  # a staff line, so it isn't uniform
+    art[:60, :60] = 0  # a corner mark, so orientation is checkable
     pix = pymupdf.Pixmap(pymupdf.csGRAY, w, h, bytearray(art.tobytes()), False)
     doc = pymupdf.open()
     for _ in range(pages):
-        page = doc.new_page(width=A4.width, height=A4.height)
+        page = doc.new_page(width=A4.width, height=A4.width * h / w)
         page.insert_image(page.rect, pixmap=pix)
+        page.set_rotation(rotation)
     doc.save(path)
 
 
@@ -64,6 +70,22 @@ def main() -> int:
     assert page.min() == 0 and page.max() == 255, (page.min(), page.max())
     src.close()
 
+    # The corner mark sits top-left in an upright scan.
+    assert page[:60, :60].max() == 0 and page[:60, -60:].min() == 255
+
+    # A sideways scan comes back upright: the page's /Rotate applies to the
+    # image extracted by xref, which bypasses it. Okular gets this right and
+    # the slicer used to not.
+    sideways = tmp / "sideways.pdf"
+    _scan_pdf(sideways, pages=1, w=2332, h=1653, rotation=90)
+    src = open_source(sideways)
+    assert src.type is SourceType.RASTER
+    turned = page_raster(src, 0)
+    assert turned.shape == (2332, 1653), turned.shape
+    # Turned clockwise, so the mark that was top-left is now top-right.
+    assert turned[:60, -60:].max() == 0 and turned[:60, :60].min() == 255
+    src.close()
+
     # An override must win over detection, and say so.
     src = open_source(scan, SourceType.VECTOR)
     assert src.type is SourceType.VECTOR and src.detected is SourceType.RASTER
@@ -71,7 +93,7 @@ def main() -> int:
     assert page_raster(src, 0).shape[1] > 4000, "override must force a render"
     src.close()
 
-    for f in (vec, scan):
+    for f in (vec, scan, sideways):
         f.unlink()
     tmp.rmdir()
     print("ok")

tests/test_pdfopt.py

@@ -0,0 +1,96 @@
+"""Runnable check for optional PDF shrinking, including what it refuses to do."""
+
+from __future__ import annotations
+
+import sys
+from pathlib import Path
+
+import numpy as np
+import pymupdf
+
+sys.path.insert(0, str(Path(__file__).resolve().parents[1]))
+
+from noteman_slicer.pdfopt import MIN_DPI, optimise  # noqa: E402
+
+A4_PT = (595, 842)
+
+
+def _pdf(path: Path, width: int, height: int, *, colour: bool = False, bilevel: bool = False):
+    """One full-page image of ruled lines, at the given pixel size."""
+    art = np.full((height, width, 3), 255, np.uint8)
+    for i in range(6):
+        y = int(height * (0.2 + i * 0.03))
+        art[y : y + max(1, height // 900), int(width * 0.1) : int(width * 0.9)] = 0
+    if colour:
+        art[: height // 3, :, 0] = 40  # a strong blue cast over the top third
+        art[: height // 3, :, 1] = 90
+    grey = art[:, :, 0] if not colour else None
+
+    doc = pymupdf.open()
+    page = doc.new_page(width=A4_PT[0], height=A4_PT[1])
+    if bilevel:
+        pix = pymupdf.Pixmap(pymupdf.csGRAY, width, height, bytearray(grey.tobytes()), False)
+        page.insert_image(page.rect, pixmap=pix)
+        doc.save(path, garbage=4, deflate=True)
+        # Re-save through a 1-bit PNG so the stored image really is bilevel.
+        import cv2
+
+        ok, buf = cv2.imencode(".png", (grey > 127).astype(np.uint8) * 255)
+        doc2 = pymupdf.open()
+        p2 = doc2.new_page(width=A4_PT[0], height=A4_PT[1])
+        p2.insert_image(p2.rect, stream=buf.tobytes())
+        doc2.save(path, garbage=4, deflate=True)
+        return
+    stream = art if colour else np.dstack([grey] * 3)
+    import cv2
+
+    ok, buf = cv2.imencode(".jpg", stream, [cv2.IMWRITE_JPEG_QUALITY, 92])
+    page.insert_image(page.rect, stream=buf.tobytes())
+    doc.save(path, garbage=4, deflate=True)
+
+
+def main() -> int:
+    tmp = Path(__file__).with_name("_tmp")
+    tmp.mkdir(exist_ok=True)
+
+    # A4 is 8.26in wide, so 2480px is ~300 DPI and 800px is ~97 DPI.
+    fine, coarse, colour = tmp / "fine.pdf", tmp / "coarse.pdf", tmp / "colour.pdf"
+    _pdf(fine, 2480, 3508)
+    _pdf(coarse, 800, 1130)
+    _pdf(colour, 2480, 3508, colour=True)
+
+    data, report = optimise(pymupdf.open(fine), fine.stat().st_size)
+    assert report.converted == 1, report.summary()
+    assert data, "a greyscale scan at 300 DPI should shrink"
+    assert report.ratio < 0.9, report.ratio
+    # The result must still be a readable PDF of the same page count.
+    assert len(pymupdf.open(stream=data, filetype="pdf")) == 1
+
+    # Too coarse: staff lines would break, so it is left alone.
+    _, report = optimise(pymupdf.open(coarse), coarse.stat().st_size)
+    assert report.converted == 0, report.summary()
+    assert any("DPI" in reason for reason in report.skipped), report.skipped
+
+    # Genuine colour: artwork is not thrown away.
+    _, report = optimise(pymupdf.open(colour), colour.stat().st_size)
+    assert report.converted == 0, report.summary()
+    assert any("colour" in reason for reason in report.skipped), report.skipped
+
+    # A no-op run reports honestly rather than returning something bigger.
+    empty = pymupdf.open()
+    empty.new_page()
+    data, report = optimise(empty, 1)
+    assert data == b"" and report.converted == 0
+    assert report.ratio == 1.0
+
+    assert MIN_DPI >= 150, "the floor exists to protect thin staff lines"
+
+    for f in (fine, coarse, colour):
+        f.unlink(missing_ok=True)
+    tmp.rmdir()
+    print("ok")
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())

tests/test_render.py

@@ -19,6 +19,7 @@ from noteman_slicer.pdf import open_source, page_raster  # noqa: E402
 from noteman_slicer.project import Cut, Project, default_path  # noqa: E402
 from noteman_slicer.render import (  # noqa: E402
     ALPHA_LEVELS,
+    _ink_bbox,
     apply_levels,
     encode,
     pad_right,
@@ -87,6 +88,19 @@ def main() -> int:
     assert rgba[:, :, 3].min() == 0, "paper must be fully transparent"
     assert len(np.unique(rgba[:, :, 3])) <= ALPHA_LEVELS
 
+    # Trim keeps a line of lyrics and drops a fleck. Each letter is its own
+    # small blob, so judging blobs by area threw the whole line away and the
+    # bottom voice lost its words; a fleck's row carries almost no ink at all.
+    art = np.full((300, 800), 255, np.uint8)
+    art[100:150, 50:750] = 0  # a staff
+    for x in range(60, 700, 30):  # lyrics: many small glyphs, one row
+        art[200:220, x : x + 14] = 0
+    art[5:9, 10:14] = 0  # a fleck in the far corner
+    x0, y0, x1, y1 = _ink_bbox(art)
+    assert (y0, y1) == (100, 220), f"lyrics kept, fleck dropped: {(y0, y1)}"
+    assert (x0, x1) == (50, 750), (x0, x1)
+    assert _ink_bbox(np.full((50, 50), 255, np.uint8)) is None, "blank slice has no box"
+
     # Levels: a white point below the paper value wipes the paper out entirely.
     faint = np.full((10, 10), 200, np.uint8)
     assert apply_levels(faint, 0, 180).max() == 255