Initial commit

Covers.py

@@ -0,0 +1,58 @@
+"""Small versions of cover art. Embedded covers can be several megabytes,
+and everything shown goes through Flet's connection, so the album grid and
+play bar get thumbnails, cached in ~/.cache/SaraSuite/SaraTune/Covers/."""
+
+import hashlib
+import io
+from pathlib import Path
+from typing import Optional
+
+from PIL import Image, UnidentifiedImageError
+
+from Core import CacheDir
+from Metadata import ReadCover
+
+CoversDir = CacheDir / "Covers"
+_NoCover = b""  # remembered in the memory cache so a coverless album isn't read again
+
+
+def Thumbnail(Data: bytes, Size: int) -> Optional[bytes]:
+    try:
+        with Image.open(io.BytesIO(Data)) as Picture:
+            Picture = Picture.convert("RGB")
+            Picture.thumbnail((Size, Size), Image.LANCZOS)
+            Output = io.BytesIO()
+            Picture.save(Output, "JPEG", quality=88)
+            return Output.getvalue()
+    except (UnidentifiedImageError, OSError, ValueError, Image.DecompressionBombError):
+        return None
+
+
+_Memory: dict[tuple[str, int], bytes] = {}
+
+
+def CoverFor(FilePath: str, Size: int) -> Optional[bytes]:
+    """FilePath's cover at most Size pixels wide. Blocking (run it in a
+    thread). Cached on disk by path, size and the file's mtime."""
+    Key = (FilePath, Size)
+    if Key in _Memory:
+        return _Memory[Key] or None
+    try:
+        Stamp = Path(FilePath).stat().st_mtime_ns
+    except OSError:
+        return None
+    Name = hashlib.sha1(f"{FilePath}|{Size}|{Stamp}".encode("utf-8", "surrogateescape")).hexdigest()
+    CachePath = CoversDir / f"{Name}.jpg"
+    if CachePath.exists():
+        Data = CachePath.read_bytes()
+    else:
+        Original = ReadCover(FilePath)
+        Data = Thumbnail(Original, Size) if Original else None
+        if Data:
+            try:
+                CoversDir.mkdir(parents=True, exist_ok=True)
+                CachePath.write_bytes(Data)
+            except OSError:
+                pass
+    _Memory[Key] = Data or _NoCover
+    return Data