add sheet music OCR CLI tool using Audiveris

Adds a Typer CLI (sheet-music-ocr) that converts scanned sheet music
(PDF, PNG, JPG, TIFF) to MusicXML via Audiveris, preserving lyrics and
text annotations. Includes Audiveris in the nix dev shell.

https://claude.ai/code/session_017GqUbuRDT58toRaxMtfRmf

pyproject.toml

@@ -27,6 +27,7 @@ dependencies = [
 [project.scripts]
 database = "python.database_cli:app"
 van-inventory = "python.van_inventory.main:serve"
+sheet-music-ocr = "python.sheet_music_ocr.main:app"
 
 [dependency-groups]
 dev = [

python/sheet_music_ocr/__init__.py

@@ -0,0 +1 @@
+"""Sheet music OCR tool using Audiveris."""

python/sheet_music_ocr/audiveris.py

@@ -0,0 +1,62 @@
+"""Audiveris subprocess wrapper for optical music recognition."""
+
+from __future__ import annotations
+
+import shutil
+import subprocess
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from pathlib import Path
+
+
+class AudiverisError(Exception):
+    """Raised when Audiveris processing fails."""
+
+
+def find_audiveris() -> str:
+    """Find the Audiveris executable on PATH.
+
+    Returns:
+        Path to the audiveris executable.
+
+    Raises:
+        AudiverisError: If Audiveris is not found.
+    """
+    path = shutil.which("audiveris")
+    if not path:
+        msg = "Audiveris not found on PATH. Install it via 'nix develop' or add it to your environment."
+        raise AudiverisError(msg)
+    return path
+
+
+def run_audiveris(input_path: Path, output_dir: Path) -> Path:
+    """Run Audiveris on an input file and return the path to the generated .mxl.
+
+    Args:
+        input_path: Path to the input sheet music file (PDF, PNG, JPG, TIFF).
+        output_dir: Directory where Audiveris will write its output.
+
+    Returns:
+        Path to the generated .mxl file.
+
+    Raises:
+        AudiverisError: If Audiveris fails or produces no output.
+    """
+    audiveris = find_audiveris()
+    result = subprocess.run(
+        [audiveris, "-batch", "-export", "-output", str(output_dir), str(input_path)],
+        capture_output=True,
+        text=True,
+        check=False,
+    )
+    if result.returncode != 0:
+        msg = f"Audiveris failed (exit {result.returncode}):\n{result.stderr}"
+        raise AudiverisError(msg)
+
+    mxl_files = list(output_dir.rglob("*.mxl"))
+    if not mxl_files:
+        msg = f"Audiveris produced no .mxl output in {output_dir}"
+        raise AudiverisError(msg)
+
+    return mxl_files[0]

python/sheet_music_ocr/main.py

@@ -0,0 +1,88 @@
+"""CLI tool for converting scanned sheet music to MusicXML.
+
+Usage:
+    sheet-music-ocr scan.pdf
+    sheet-music-ocr scan.png -o output.mxml
+"""
+
+from __future__ import annotations
+
+import tempfile
+import zipfile
+from pathlib import Path
+from typing import Annotated
+
+import typer
+
+from python.sheet_music_ocr.audiveris import AudiverisError, run_audiveris
+
+SUPPORTED_EXTENSIONS = {".pdf", ".png", ".jpg", ".jpeg", ".tiff", ".tif"}
+
+app = typer.Typer(help="Convert scanned sheet music to MusicXML using Audiveris.")
+
+
+def extract_mxml_from_mxl(mxl_path: Path, output_path: Path) -> Path:
+    """Extract the MusicXML file from an .mxl archive.
+
+    An .mxl file is a ZIP archive containing one or more .xml MusicXML files.
+
+    Args:
+        mxl_path: Path to the .mxl file.
+        output_path: Path where the extracted .mxml file should be written.
+
+    Returns:
+        The output path.
+
+    Raises:
+        FileNotFoundError: If no MusicXML file is found inside the archive.
+    """
+    with zipfile.ZipFile(mxl_path, "r") as zf:
+        xml_names = [n for n in zf.namelist() if n.endswith(".xml") and not n.startswith("META-INF")]
+        if not xml_names:
+            msg = f"No MusicXML (.xml) file found inside {mxl_path}"
+            raise FileNotFoundError(msg)
+        with zf.open(xml_names[0]) as src, output_path.open("wb") as dst:
+            dst.write(src.read())
+    return output_path
+
+
+@app.command()
+def convert(
+    input_file: Annotated[Path, typer.Argument(help="Path to sheet music scan (PDF, PNG, JPG, TIFF).")],
+    output: Annotated[
+        Path | None,
+        typer.Option("--output", "-o", help="Output .mxml file path. Defaults to <input_stem>.mxml."),
+    ] = None,
+) -> None:
+    """Convert a scanned sheet music file to MusicXML."""
+    if not input_file.exists():
+        typer.echo(f"Error: {input_file} does not exist.", err=True)
+        raise typer.Exit(code=1)
+
+    if input_file.suffix.lower() not in SUPPORTED_EXTENSIONS:
+        typer.echo(
+            f"Error: Unsupported format '{input_file.suffix}'. Supported: {', '.join(sorted(SUPPORTED_EXTENSIONS))}",
+            err=True,
+        )
+        raise typer.Exit(code=1)
+
+    output_path = output or input_file.with_suffix(".mxml")
+
+    with tempfile.TemporaryDirectory() as tmpdir:
+        try:
+            mxl_path = run_audiveris(input_file, Path(tmpdir))
+        except AudiverisError as e:
+            typer.echo(f"Error: {e}", err=True)
+            raise typer.Exit(code=1) from e
+
+        try:
+            extract_mxml_from_mxl(mxl_path, output_path)
+        except FileNotFoundError as e:
+            typer.echo(f"Error: {e}", err=True)
+            raise typer.Exit(code=1) from e
+
+    typer.echo(f"Written: {output_path}")
+
+
+if __name__ == "__main__":
+    app()

shell.nix

@@ -14,6 +14,8 @@
       ssh-to-age
       gnupg
       age
+
+      audiveris
     ];
   };
 }

tests/test_sheet_music_ocr.py

@@ -0,0 +1,154 @@
+import zipfile
+from unittest.mock import patch
+
+import pytest
+from typer.testing import CliRunner
+
+from python.sheet_music_ocr.audiveris import AudiverisError, find_audiveris, run_audiveris
+from python.sheet_music_ocr.main import SUPPORTED_EXTENSIONS, app, extract_mxml_from_mxl
+
+runner = CliRunner()
+
+
+def make_mxl(path, xml_content=b"<score-partwise/>"):
+    """Create a minimal .mxl (ZIP) file with a MusicXML inside."""
+    with zipfile.ZipFile(path, "w") as zf:
+        zf.writestr("score.xml", xml_content)
+
+
+class TestExtractMxmlFromMxl:
+    def test_extracts_xml(self, tmp_path):
+        mxl = tmp_path / "test.mxl"
+        output = tmp_path / "output.mxml"
+        content = b"<score-partwise>hello</score-partwise>"
+        make_mxl(mxl, content)
+
+        result = extract_mxml_from_mxl(mxl, output)
+
+        assert result == output
+        assert output.read_bytes() == content
+
+    def test_skips_meta_inf(self, tmp_path):
+        mxl = tmp_path / "test.mxl"
+        output = tmp_path / "output.mxml"
+        with zipfile.ZipFile(mxl, "w") as zf:
+            zf.writestr("META-INF/container.xml", "<container/>")
+            zf.writestr("score.xml", b"<score/>")
+
+        extract_mxml_from_mxl(mxl, output)
+
+        assert output.read_bytes() == b"<score/>"
+
+    def test_raises_when_no_xml(self, tmp_path):
+        mxl = tmp_path / "test.mxl"
+        output = tmp_path / "output.mxml"
+        with zipfile.ZipFile(mxl, "w") as zf:
+            zf.writestr("readme.txt", "no xml here")
+
+        with pytest.raises(FileNotFoundError, match="No MusicXML"):
+            extract_mxml_from_mxl(mxl, output)
+
+
+class TestFindAudiveris:
+    def test_raises_when_not_found(self):
+        with (
+            patch("python.sheet_music_ocr.audiveris.shutil.which", return_value=None),
+            pytest.raises(AudiverisError, match="not found"),
+        ):
+            find_audiveris()
+
+    def test_returns_path_when_found(self):
+        with patch("python.sheet_music_ocr.audiveris.shutil.which", return_value="/usr/bin/audiveris"):
+            assert find_audiveris() == "/usr/bin/audiveris"
+
+
+class TestRunAudiveris:
+    def test_raises_on_nonzero_exit(self, tmp_path):
+        with (
+            patch("python.sheet_music_ocr.audiveris.find_audiveris", return_value="audiveris"),
+            patch("python.sheet_music_ocr.audiveris.subprocess.run") as mock_run,
+        ):
+            mock_run.return_value.returncode = 1
+            mock_run.return_value.stderr = "something went wrong"
+
+            with pytest.raises(AudiverisError, match="failed"):
+                run_audiveris(tmp_path / "input.pdf", tmp_path / "output")
+
+    def test_raises_when_no_mxl_produced(self, tmp_path):
+        output_dir = tmp_path / "output"
+        output_dir.mkdir()
+
+        with (
+            patch("python.sheet_music_ocr.audiveris.find_audiveris", return_value="audiveris"),
+            patch("python.sheet_music_ocr.audiveris.subprocess.run") as mock_run,
+        ):
+            mock_run.return_value.returncode = 0
+
+            with pytest.raises(AudiverisError, match=r"no \.mxl output"):
+                run_audiveris(tmp_path / "input.pdf", output_dir)
+
+    def test_returns_mxl_path(self, tmp_path):
+        output_dir = tmp_path / "output"
+        output_dir.mkdir()
+        mxl = output_dir / "score.mxl"
+        make_mxl(mxl)
+
+        with (
+            patch("python.sheet_music_ocr.audiveris.find_audiveris", return_value="audiveris"),
+            patch("python.sheet_music_ocr.audiveris.subprocess.run") as mock_run,
+        ):
+            mock_run.return_value.returncode = 0
+
+            result = run_audiveris(tmp_path / "input.pdf", output_dir)
+            assert result == mxl
+
+
+class TestCli:
+    def test_missing_input_file(self, tmp_path):
+        result = runner.invoke(app, [str(tmp_path / "nonexistent.pdf")])
+        assert result.exit_code == 1
+        assert "does not exist" in result.output
+
+    def test_unsupported_format(self, tmp_path):
+        bad_file = tmp_path / "music.bmp"
+        bad_file.touch()
+        result = runner.invoke(app, [str(bad_file)])
+        assert result.exit_code == 1
+        assert "Unsupported format" in result.output
+
+    def test_supported_extensions_complete(self):
+        assert ".pdf" in SUPPORTED_EXTENSIONS
+        assert ".png" in SUPPORTED_EXTENSIONS
+        assert ".jpg" in SUPPORTED_EXTENSIONS
+        assert ".jpeg" in SUPPORTED_EXTENSIONS
+        assert ".tiff" in SUPPORTED_EXTENSIONS
+
+    def test_successful_conversion(self, tmp_path):
+        input_file = tmp_path / "score.pdf"
+        input_file.touch()
+        output_file = tmp_path / "score.mxml"
+
+        mxl_path = tmp_path / "tmp_mxl" / "score.mxl"
+        mxl_path.parent.mkdir()
+        make_mxl(mxl_path, b"<score-partwise/>")
+
+        with patch("python.sheet_music_ocr.main.run_audiveris", return_value=mxl_path):
+            result = runner.invoke(app, [str(input_file), "-o", str(output_file)])
+
+        assert result.exit_code == 0
+        assert output_file.exists()
+        assert "Written" in result.output
+
+    def test_default_output_path(self, tmp_path):
+        input_file = tmp_path / "score.png"
+        input_file.touch()
+
+        mxl_path = tmp_path / "tmp_mxl" / "score.mxl"
+        mxl_path.parent.mkdir()
+        make_mxl(mxl_path)
+
+        with patch("python.sheet_music_ocr.main.run_audiveris", return_value=mxl_path):
+            result = runner.invoke(app, [str(input_file)])
+
+        assert result.exit_code == 0
+        assert (tmp_path / "score.mxml").exists()