Rhythm Selection & Cleanup

generator/engraving/validation.py

@@ -0,0 +1,43 @@
+from __future__ import annotations
+
+import hashlib
+import io
+import pathlib
+import re
+
+import PIL.Image
+import PIL.ImageChops
+
+import generator.engraving.types
+
+ENGINE_NAME = 'Vamp Python'
+PAGE_WIDTH = 976
+PAGE_HEIGHT = 484
+
+def check_content(data: bytes, name: str) -> None:
+  with PIL.Image.open(io.BytesIO(data)) as image:
+    if image.format != 'PNG' or image.size != (PAGE_WIDTH, PAGE_HEIGHT):
+      raise generator.engraving.types.EngravingError(f'{name}: expected a {PAGE_WIDTH}x{PAGE_HEIGHT} PNG page')
+    image.load()
+    white = PIL.Image.new('RGBA', image.size, 'white')
+    white.alpha_composite(image.convert('RGBA'))
+    ink = PIL.ImageChops.difference(white.convert('RGB'), PIL.Image.new('RGB', image.size, 'white')).convert('L').point(lambda x: 255 if x > 32 else 0)
+    bounds = ink.getbbox()
+    if not bounds:
+      raise generator.engraving.types.EngravingError(f'{name}: engraver produced a blank page')
+    if bounds[0] < 4 or bounds[1] < 4 or bounds[2] > PAGE_WIDTH - 4 or bounds[3] > PAGE_HEIGHT - 4:
+      raise generator.engraving.types.EngravingError(f'{name}: notation reaches the page edge; refusing potentially clipped output')
+
+def check_page(path: pathlib.Path, validated_pages: set[str] | None = None, *, expected_sha256: str | None = None) -> str:
+  # Trust content, never a filename or a caller-supplied checksum alone.
+  if path.is_symlink() or not path.is_file():
+    raise generator.engraving.types.EngravingError(f'{path.name}: expected a regular PNG file')
+  data = path.read_bytes()
+  digest = hashlib.sha256(data).hexdigest()
+  if expected_sha256 is not None and (not isinstance(expected_sha256, str) or not re.fullmatch('[0-9a-f]{64}', expected_sha256) or digest != expected_sha256):
+    raise generator.engraving.types.EngravingError(f'{path.name}: score page checksum mismatch')
+  if validated_pages is None or digest not in validated_pages:
+    check_content(data, path.name)
+    if validated_pages is not None:
+      validated_pages.add(digest)
+  return digest