diff --git a/datumaro/datumaro/util/image.py b/datumaro/datumaro/util/image.py
index 784a1218772..02364de90ea 100644
--- a/datumaro/datumaro/util/image.py
+++ b/datumaro/datumaro/util/image.py
@@ -28,7 +28,7 @@ def load_image(path):
 
     if _IMAGE_BACKEND == _IMAGE_BACKENDS.cv2:
         import cv2
-        image = cv2.imread(path)
+        image = cv2.imread(path, cv2.IMREAD_UNCHANGED)
         image = image.astype(np.float32)
     elif _IMAGE_BACKEND == _IMAGE_BACKENDS.PIL:
         from PIL import Image
@@ -39,13 +39,15 @@ def load_image(path):
     else:
         raise NotImplementedError()
 
-    assert len(image.shape) == 3
-    assert image.shape[2] in [1, 3, 4]
+    assert len(image.shape) in [2, 3]
+    if len(image.shape) == 3:
+        assert image.shape[2] in [3, 4]
     return image
 
 def save_image(path, image, params=None):
     if _IMAGE_BACKEND == _IMAGE_BACKENDS.cv2:
         import cv2
+        image = image.astype(np.uint8)
         cv2.imwrite(path, image, params=params)
     elif _IMAGE_BACKEND == _IMAGE_BACKENDS.PIL:
         from PIL import Image
@@ -109,8 +111,9 @@ def decode_image(image_bytes):
     else:
         raise NotImplementedError()
 
-    assert len(image.shape) == 3
-    assert image.shape[2] in [1, 3, 4]
+    assert len(image.shape) in [2, 3]
+    if len(image.shape) == 3:
+        assert image.shape[2] in [3, 4]
     return image
 
 
diff --git a/datumaro/tests/test_image.py b/datumaro/tests/test_image.py
index 143d6c4e41e..424fd9c88dd 100644
--- a/datumaro/tests/test_image.py
+++ b/datumaro/tests/test_image.py
@@ -17,9 +17,12 @@ def tearDown(self):
 
     def test_save_and_load_backends(self):
         backends = image_module._IMAGE_BACKENDS
-        for save_backend, load_backend in product(backends, backends):
+        for save_backend, load_backend, c in product(backends, backends, [1, 3]):
             with TestDir() as test_dir:
-                src_image = np.random.randint(0, 255 + 1, (2, 4, 3))
+                if c == 1:
+                    src_image = np.random.randint(0, 255 + 1, (2, 4))
+                else:
+                    src_image = np.random.randint(0, 255 + 1, (2, 4, c))
                 path = osp.join(test_dir.path, 'img.png') # lossless
 
                 image_module._IMAGE_BACKEND = save_backend
@@ -33,8 +36,11 @@ def test_save_and_load_backends(self):
 
     def test_encode_and_decode_backends(self):
         backends = image_module._IMAGE_BACKENDS
-        for save_backend, load_backend in product(backends, backends):
-            src_image = np.random.randint(0, 255 + 1, (2, 4, 3))
+        for save_backend, load_backend, c in product(backends, backends, [1, 3]):
+            if c == 1:
+                src_image = np.random.randint(0, 255 + 1, (2, 4))
+            else:
+                src_image = np.random.randint(0, 255 + 1, (2, 4, c))
 
             image_module._IMAGE_BACKEND = save_backend
             buffer = image_module.encode_image(src_image, '.png') # lossless