[Model] add style transfer model (#922)

* add style transfer model

* add examples for generation model

* add unit test

* add speed comparison

* add speed comparison

* add variable for constant

* add preprocessor and postprocessor

* add preprocessor and postprocessor

* fix

* fix according to review

Co-authored-by: DefTruth <31974251+DefTruth@users.noreply.github.com>

examples/vision/generation/anemigan/python/README.md

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+# AnimeGAN Python部署示例
+
+在部署前，需确认以下两个步骤
+
+- 1. 软硬件环境满足要求，参考[FastDeploy环境要求](../../../../../docs/cn/build_and_install/download_prebuilt_libraries.md)  
+- 2. FastDeploy Python whl包安装，参考[FastDeploy Python安装](../../../../../docs/cn/build_and_install/download_prebuilt_libraries.md)
+
+本目录下提供`infer.py`快速完成AnimeGAN在CPU/GPU，以及GPU上通过TensorRT加速部署的示例。执行如下脚本即可完成
+
+```bash
+# 下载部署示例代码
+git clone https://github.com/PaddlePaddle/FastDeploy.git
+cd FastDeploy/examples/vision/generation/anemigan/python
+# 下载准备好的测试图片
+wget https://bj.bcebos.com/paddlehub/fastdeploy/style_transfer_testimg.jpg
+
+# CPU推理
+python infer.py --model animegan_v1_hayao_60  --image style_transfer_testimg.jpg  --device cpu
+# GPU推理
+python infer.py --model animegan_v1_hayao_60 --image style_transfer_testimg.jpg  --device gpu
+```
+
+## AnimeGAN Python接口
+
+```python
+fd.vision.generation.AnimeGAN(model_file, params_file, runtime_option=None, model_format=ModelFormat.PADDLE)
+```
+
+AnimeGAN模型加载和初始化，其中model_file和params_file为用于Paddle inference的模型结构文件和参数文件。
+
+**参数**
+
+> * **model_file**(str): 模型文件路径
+> * **params_file**(str): 参数文件路径
+> * **runtime_option**(RuntimeOption): 后端推理配置，默认为None，即采用默认配置
+> * **model_format**(ModelFormat): 模型格式，默认为Paddle格式
+
+
+### predict函数
+
+> ```python
+> AnimeGAN.predict(input_image)
+> ```
+>
+> 模型预测入口，输入图像输出风格迁移后的结果。
+>
+> **参数**
+>
+> > * **input_image**(np.ndarray): 输入数据，注意需为HWC，BGR格式
+
+> **返回** np.ndarray, 风格转换后的图像，BGR格式
+
+### batch_predict函数
+> ```python
+> AnimeGAN.batch_predict函数(input_images)
+> ```
+>
+> 模型预测入口，输入一组图像并输出风格迁移后的结果。
+>
+> **参数**
+>
+> > * **input_images**(list(np.ndarray)): 输入数据，一组图像数据，注意需为HWC，BGR格式
+
+> **返回** list(np.ndarray), 风格转换后的一组图像，BGR格式
+
+## 其它文档
+
+- [风格迁移 模型介绍](..)
+- [C++部署](../cpp)
+- [如何切换模型推理后端引擎](../../../../../docs/cn/faq/how_to_change_backend.md)

examples/vision/generation/anemigan/python/infer.py

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+import cv2
+import os
+import fastdeploy as fd
+
+
+def parse_arguments():
+    import argparse
+    import ast
+    parser = argparse.ArgumentParser()
+    parser.add_argument("--model", required=True, help="Name of the model.")
+    parser.add_argument(
+        "--image", type=str, required=True, help="Path of test image file.")
+    parser.add_argument(
+        "--device",
+        type=str,
+        default='cpu',
+        help="Type of inference device, support 'cpu' or 'gpu'.")
+    return parser.parse_args()
+
+
+def build_option(args):
+    option = fd.RuntimeOption()
+    if args.device.lower() == "gpu":
+        option.use_gpu()
+    else:
+        option.set_paddle_mkldnn(False)
+    return option
+
+
+args = parse_arguments()
+
+# 配置runtime，加载模型
+runtime_option = build_option(args)
+fd.download_model(name=args.model, path='./', format='paddle')
+model_file = os.path.join(args.model, "model.pdmodel")
+params_file = os.path.join(args.model, "model.pdiparams")
+model = fd.vision.generation.AnimeGAN(
+    model_file, params_file, runtime_option=runtime_option)
+
+# 预测图片并保存结果
+im = cv2.imread(args.image)
+result = model.predict(im)
+cv2.imwrite('style_transfer_result.png', result)