update the readme.

Signed-off-by: wxywb <xy.wang@zilliz.com>

README.md

@@ -1,2 +1,110 @@
-# slip
+# Image-Text Retrieval Embdding with SLIP
+
+*author: David Wang*
+
+
+<br />
+
+
+
+## Description
+
+This operator extracts features for image or text with [SLIP](https://arxiv.org/abs/2112.12750), a multi-task learning framework for combining self-supervised learning and CLIP pre-training. This is an adaptation from [facebookresearch/SLIP](https://github.com/facebookresearch/SLIP).
+
+
+<br />
+
+
+## Code Example
+
+Load an image from path './teddy.jpg' to generate an image embedding. 
+
+Read the text 'A teddybear on a skateboard in Times Square.' to generate an text embedding. 
+
+ *Write the pipeline in simplified style*:
+
+```python
+import towhee
+
+towhee.glob('./moon.jpeg') \
+      .image_decode() \
+      .image_text_embedding.slip(model_name='slip_vit_small', modality='image') \
+      .show()
+
+towhee.dc(['moon in the night.']) \
+      .image_text_embedding.slip(model_name='slip_vit_small', modality='text') \
+      .show()
+```
+<img src="./vec1.png" alt="result1" style="height:20px;"/>
+<img src="./vec2.png" alt="result2" style="height:20px;"/>
+
+*Write a same pipeline with explicit inputs/outputs name specifications:*
+
+```python
+import towhee
+
+towhee.glob['path']('./moon.jpeg') \
+      .image_decode['path', 'img']() \
+      .image_text_embedding.slip['img', 'vec'](model_name='slip_vit_small', modality='image') \
+      .select['img', 'vec']() \
+      .show()
+
+towhee.dc['text'](['moon in the night.']) \
+      .image_text_embedding.slip['text','vec'](model_name= 'slip_vit_small', modality='text') \
+      .select['text', 'vec']() \
+      .show()
+```
+<img src="./tabular1.png" alt="result1" style="height:60px;"/>
+<img src="./tabular2.png" alt="result2" style="height:60px;"/>
+
+
+<br />
+
+
+
+## Factory Constructor
+
+Create the operator via the following factory method
+
+***slip(model_name, modality)***
+
+**Parameters:**
+
+​   ***model_name:*** *str*
+
+​   The model name of SLIP. Supported model names: 
+- slip_vit_small
+- slip_vit_base
+- slip_vit_large
+
+
+​   ***modality:*** *str*
+
+​   Which modality(*image* or *text*) is used to generate the embedding. 
+
+<br />
+
+
+
+## Interface
+
+An image-text embedding operator takes a [towhee image](link/to/towhee/image/api/doc) or string as input and generate an embedding in ndarray.
+
+
+**Parameters:**
+
+​	***data:*** *towhee.types.Image (a sub-class of numpy.ndarray)*  or *str*
+
+​  The data (image or text based on specified modality) to generate embedding.	
+
+
+
+**Returns:** *numpy.ndarray*
+
+​   The data embedding extracted by model.
+
+
+
+
+