diff --git a/ppcls/data/preprocess/ops/operators.py b/ppcls/data/preprocess/ops/operators.py
index b706dbd9a0ef87c29131b5c6f2dcb7c0a89d45d4..e617b8a71afffeb9e18e4be412f5a3374bd387ec 100644
--- a/ppcls/data/preprocess/ops/operators.py
+++ b/ppcls/data/preprocess/ops/operators.py
@@ -140,13 +140,12 @@ class DecodeImage(object):
     """ decode image """
 
     def __init__(self,
+                 to_np=True,
                  to_rgb=True,
-                 to_np=False,
                  channel_first=False,
-                 backend="cv2",
-                 return_numpy=True):
-        self.to_rgb = to_rgb
+                 backend="cv2"):
         self.to_np = to_np  # to numpy
+        self.to_rgb = to_rgb  # only enabled when to_np is True
         self.channel_first = channel_first  # only enabled when to_np is True
 
         if backend.lower() not in ["cv2", "pil"]:
@@ -156,38 +155,33 @@ class DecodeImage(object):
             backend = "cv2"
         self.backend = backend.lower()
 
-        if not return_numpy:
-            assert to_rgb, f"\"to_rgb\" must be True while \"return_numpy\" is False."
-            assert not channel_first, f"\"channel_first\" must be False while \"return_numpy\" is False."
-        self.return_numpy = return_numpy
+        if not to_np:
+            logger.warning(
+                f"\"to_rgb\" and \"channel_first\" are only enabled when to_np is True. \"to_np\" is now {to_np}."
+            )
 
     def __call__(self, img):
         if isinstance(img, Image.Image):
-            if self.return_numpy:
-                img = np.asarray(img)[:, :, ::-1]  # to bgr
+            assert self.backend == "pil", "invalid input 'img' in DecodeImage"
         elif isinstance(img, np.ndarray):
-            assert self.return_numpy, "invalid input 'img' in DecodeImage"
-        else:
-            if six.PY2:
-                assert type(img) is str and len(
-                    img) > 0, "invalid input 'img' in DecodeImage"
-            else:
-                assert type(img) is bytes and len(
-                    img) > 0, "invalid input 'img' in DecodeImage"
-
+            assert self.backend == "cv2", "invalid input 'img' in DecodeImage"
+        elif isinstance(img, bytes):
             if self.backend == "pil":
                 data = io.BytesIO(img)
-                img = Image.open(data).convert("RGB")
-                if self.return_numpy:
-                    img = np.asarray(img)[:, :, ::-1]  # to bgr
+                img = Image.open(data)
             else:
-                data = np.frombuffer(img, dtype='uint8')
+                data = np.frombuffer(img, dtype="uint8")
                 img = cv2.imdecode(data, 1)
+        else:
+            raise ValueError("invalid input 'img' in DecodeImage")
+
+        if self.to_np:
+            if self.backend == "pil":
+                assert img.mode == "RGB", f"invalid shape of image[{img.shape}]"
+                img = np.asarray(img)[:, :, ::-1]  # BRG
 
-        if self.return_numpy:
             if self.to_rgb:
-                assert img.shape[2] == 3, 'invalid shape of image[%s]' % (
-                    img.shape)
+                assert img.shape[2] == 3, f"invalid shape of image[{img.shape}]"
                 img = img[:, :, ::-1]
 
             if self.channel_first: