Make normalization optional

Closes #216 (closed)

dan/ocr/predict/inference.py

@@ -109,8 +109,8 @@ class DAN:
             )
 
         self.mean, self.std = (
-            torch.tensor(parameters["mean"]) / 255,
-            torch.tensor(parameters["std"]) / 255,
+            torch.tensor(parameters["mean"]) / 255 if "mean" in parameters else None,
+            torch.tensor(parameters["std"]) / 255 if "std" in parameters else None,
         )
         self.preprocessing_transforms = get_preprocessing_transforms(
             parameters.get("preprocessings", [])
@@ -124,11 +124,21 @@ class DAN:
         """
         image = read_image(path)
         preprocessed_image = self.preprocessing_transforms(image)
-        normalized_image = torch.zeros(preprocessed_image.shape)
-        for ch in range(preprocessed_image.shape[0]):
+
+        if self.mean is None and self.std is None:
+            return preprocessed_image, preprocessed_image
+
+        size = preprocessed_image.shape
+        normalized_image = torch.zeros(size)
+
+        mean = self.mean if self.mean is not None else torch.zeros(size[0])
+        std = self.std if self.std is not None else torch.ones(size[0])
+
+        for ch in range(size[0]):
             normalized_image[ch, :, :] = (
-                preprocessed_image[ch, :, :] - self.mean[ch]
-            ) / self.std[ch]
+                preprocessed_image[ch, :, :] - mean[ch]
+            ) / std[ch]
+
         return preprocessed_image, normalized_image
 
     def predict(