Optimize README

Signed-off-by: Jael Gu <mengjia.gu@zilliz.com>

README.md

@@ -50,33 +50,34 @@ Create the operator via the following factory method
 
 **Parameters:**
 
-​	***model_name***: *str*
+​   ***model_name***: *str*
 
-​	The model name in string. The default value is "resnet34".
+​   The model name in string. The default value is "resnet34".
 Refer [Timm Docs](https://fastai.github.io/timmdocs/#List-Models-with-Pretrained-Weights) to get a full list of supported models.
 
 
-​	***num_classes***: *int*
+​   ***num_classes***: *int*
 
-​	The number of classes. The default value is 1000.
+​   The number of classes. The default value is 1000.
 It is related to model and dataset.
 
 ​   ***skip_preprocess***: *bool*
 
-​   Flag to control whether to skip image preprocess, defaults to False.
-If set to True, image preprocess steps such as transform, normalization will be skipped.
-In this case, the user should guarantee that all the input images are already reprocessed properly, and thus can be fed to model directly.
+​   The flag to control whether to skip image preprocess.
+The default value is False.
+If set to True, it will skip image preprocessing steps (transforms).
+In this case, input image data must be prepared in advance in order to properly fit the model.
 
 
 ## Interface
 
-An image embedding operator takes an image in ndarray as input.
+An image embedding operator takes a [towhee image](link/to/towhee/image/api/doc) as input.
 It uses the pre-trained model specified by model name to generate an image embedding in ndarray.
 
 
 **Parameters:**
 
-​	***img***: *[towhee.types.Image]()*
+​	***img***: *towhee.types.Image*
 
 ​	The decoded image data in towhee.types.Image (numpy.ndarray).