Implement media preview thumbnails for Gallery

cista/app.py

@@ -16,7 +16,7 @@ from sanic.exceptions import Forbidden, NotFound
 from sanic.log import logger
 from stream_zip import ZIP_AUTO, stream_zip
 
-from cista import auth, config, session, watching
+from cista import auth, config, preview, session, watching
 from cista.api import bp
 from cista.util.apphelpers import handle_sanic_exception
 
@@ -25,6 +25,7 @@ sanic.helpers._ENTITY_HEADERS = frozenset()
 
 app = Sanic("cista", strict_slashes=True)
 app.blueprint(auth.bp)
+app.blueprint(preview.bp)
 app.blueprint(bp)
 app.exception(Exception)(handle_sanic_exception)
 

cista/preview.py

@@ -0,0 +1,40 @@
+import asyncio
+import io
+from pathlib import PurePosixPath
+from urllib.parse import unquote
+
+from PIL import Image
+from sanic import Blueprint, raw
+from sanic.exceptions import Forbidden, NotFound
+
+from cista import config
+from cista.util.filename import sanitize
+
+bp = Blueprint("preview", url_prefix="/preview")
+
+
+@bp.get("/<path:path>")
+async def preview(req, path):
+    """Preview a file"""
+    width = int(req.query_string) if req.query_string else 768
+    rel = PurePosixPath(sanitize(unquote(path)))
+    path = config.config.path / rel
+    if not path.is_file():
+        raise NotFound("File not found")
+    size = path.lstat().st_size
+    if size > 20 * 10**6:
+        raise Forbidden("File too large")
+    img = await asyncio.get_event_loop().run_in_executor(
+        req.app.ctx.threadexec, process_image, path, width
+    )
+    return raw(img, content_type="image/webp")
+
+
+def process_image(path, maxsize):
+    img = Image.open(path)
+    w, h = img.size
+    img.thumbnail((min(w, maxsize), min(h, maxsize)))
+    # Save as webp
+    imgdata = io.BytesIO()
+    img.save(imgdata, format="webp", quality=70, method=6)
+    return imgdata.getvalue()