fix alpha matting

rembg/bg.py

@@ -90,7 +90,10 @@ def remove(
     if session is None:
         session = ort_session("u2net")
 
-    mask = predict(session, np.array(img.convert("RGB"))).convert("L")
+    img = img.convert("RGB")
+
+    mask = predict(session, np.array(img))
+    mask = mask.convert("L")
     mask = mask.resize(img.size, Image.LANCZOS)
 
     if only_mask: