feat(view): serve downscaled image previews via the assets system

app/assets/services/preview.py

@@ -0,0 +1,90 @@
+import logging
+import os
+import uuid
+
+from PIL import Image, ImageOps
+
+import folder_paths
+from app.assets.database.queries.asset_reference import (
+    get_reference_by_file_path,
+    get_reference_by_id,
+    set_reference_preview,
+)
+from app.assets.services.ingest import register_file_in_place
+from app.database.db import create_session
+
+PREVIEW_TAG = "preview"
+
+
+def get_or_create_preview_file(
+    source_abs_path: str, max_size: int, quality: int
+) -> str:
+    source_hash, source_ref_id = _ensure_source_asset(source_abs_path)
+    hash_hex = source_hash.partition(":")[2]
+    preview_dir = folder_paths.get_system_user_directory("preview_cache")
+    preview_path = os.path.join(
+        preview_dir, f"{hash_hex}_{max_size}_q{quality}.webp"
+    )
+    if os.path.isfile(preview_path):
+        return preview_path
+
+    os.makedirs(preview_dir, exist_ok=True)
+    tmp_path = f"{preview_path}.{uuid.uuid4().hex}.tmp"
+    try:
+        with Image.open(source_abs_path) as img:
+            preview_img = img
+            if max(img.size) > max_size:
+                preview_img = ImageOps.contain(
+                    img, (max_size, max_size), Image.Resampling.LANCZOS
+                )
+            preview_img.save(tmp_path, format="webp", quality=quality)
+        os.replace(tmp_path, preview_path)
+    except Exception:
+        if os.path.exists(tmp_path):
+            try:
+                os.remove(tmp_path)
+            except OSError:
+                pass
+        raise
+
+    _register_preview_asset(preview_path, source_ref_id)
+    return preview_path
+
+
+def _ensure_source_asset(abs_path: str) -> tuple[str, str]:
+    abs_path = os.path.abspath(abs_path)
+    mtime_ns = os.stat(abs_path).st_mtime_ns
+
+    with create_session() as session:
+        ref = get_reference_by_file_path(session, abs_path)
+        if (
+            ref is not None
+            and ref.mtime_ns == mtime_ns
+            and ref.asset is not None
+            and ref.asset.hash
+        ):
+            return ref.asset.hash, ref.id
+
+    result = register_file_in_place(
+        abs_path=abs_path, name=os.path.basename(abs_path), tags=[]
+    )
+    if not result.asset.hash:
+        raise RuntimeError(f"asset registration produced no hash for {abs_path}")
+    return result.asset.hash, result.ref.id
+
+
+def _register_preview_asset(preview_path: str, source_ref_id: str) -> None:
+    try:
+        result = register_file_in_place(
+            abs_path=preview_path,
+            name=os.path.basename(preview_path),
+            tags=[PREVIEW_TAG],
+            mime_type="image/webp",
+        )
+        with create_session() as session:
+            source_ref = get_reference_by_id(session, source_ref_id)
+            if source_ref is not None and source_ref.preview_id is None:
+                set_reference_preview(session, source_ref_id, result.ref.id)
+            session.commit()
+    except Exception:
+        logging.warning("Failed to register preview image as asset", exc_info=True)