Esa Kataja
19f28f4da8
Levels shipped at 0–255 unless someone moved the sliders, and Bicycle Race showed what that costs. Its ink is grey, not black — a scanned engraving, ink at 2–95, paper at 163–255 — and with alpha = 255 − luminance that greyness becomes transparency. No pixel in the exported bundle was even fully opaque, and the downscale to the song's width blended every stroke edge further. Nothing downstream can rescue it. So detection proposes levels too, like it proposes cuts and skew. Notation is two-tone, which makes Otsu's split the measurement wanted; the points sit halfway from it to each end of the range, so the ramp between them survives as antialiasing rather than going jagged. A page already scanned bilevel has no interior split — Otsu degenerates to 0 — and is left alone. Per page, with the median becoming the song's, so a near-blank page cannot set them.
6.2 KiB
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
- Straighten it. If the staff lines slope, turn the Skew dial until they are level. The preview updates live.
- 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.
- 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 D. Discarded slices show hatched. D again brings one back.
- 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.
- 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. 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 D | discard it (or bring it back) |
| Drag the blue edges | resize the content rectangle |
| Shift-double-click a slice | re-engrave it |
| Page Up / Page Down | previous / next page |
| Ctrl+S | 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.