feat: relay inversé, LED idle solid, luminosité manuelle, auto-flash lux

backend/services/photobooth_service.py

@@ -162,5 +162,49 @@ class PhotoboothService:
         """Lit l'état actuel depuis le fichier private.css (ou depuis la config)."""
         return self._cfg.show_delete_button
 
+    async def get_liveview_snapshot(self) -> bytes | None:
+        """Tente de recuperer une frame JPEG du liveview de photobooth-app.
+
+        Essaie dans l'ordre :
+        1. /api/stream/snapshot — endpoint snapshot direct (si disponible)
+        2. /stream.mjpg — flux MJPEG classique, extrait la premiere frame
+        3. /api/stream — flux MJPEG alternatif
+
+        Retourne des bytes JPEG ou None si rien n'est disponible.
+        """
+        # 1. Snapshot direct
+        for path in ("/api/stream/snapshot",):
+            try:
+                async with httpx.AsyncClient(timeout=2.0) as client:
+                    r = await client.get(f"{self._base}{path}")
+                    if r.status_code == 200:
+                        ct = r.headers.get("content-type", "")
+                        if "jpeg" in ct or "image" in ct:
+                            return r.content
+            except Exception as e:
+                logger.debug("Snapshot %s: %s", path, e)
+
+        # 2. Premiere frame d'un flux MJPEG
+        for path in ("/stream.mjpg", "/api/stream"):
+            try:
+                async with httpx.AsyncClient(timeout=3.0) as client:
+                    async with client.stream("GET", f"{self._base}{path}") as resp:
+                        if resp.status_code != 200:
+                            continue
+                        buf = b""
+                        async for chunk in resp.aiter_bytes(4096):
+                            buf += chunk
+                            start = buf.find(b"\xff\xd8")
+                            if start >= 0:
+                                end = buf.find(b"\xff\xd9", start)
+                                if end >= 0:
+                                    return buf[start:end + 2]
+                            if len(buf) > 500_000:
+                                break
+            except Exception as e:
+                logger.debug("MJPEG %s: %s", path, e)
+
+        return None
+
     async def close(self):
         await self._client.aclose()