add serving doc and demo

docs/zh_CN/extension/paddle_serving.md

 # 模型服务化部署
 
-[Paddle Serving](https://github.com/PaddlePaddle/Serving) 旨在帮助深度学习开发者轻易部署在线预测服务，支持一键部署工业级的服务能力、客户端和服务端之间高并发和高效通信、并支持多种编程语言开发客户端等特点，详细使用请参考 [Paddle Serving 相关文档](https://github.com/PaddlePaddle/Serving)。
+## 一、简介
+[Paddle Serving](https://github.com/PaddlePaddle/Serving) 旨在帮助深度学习开发者轻易部署在线预测服务，支持一键部署工业级的服务能力、客户端和服务端之间高并发和高效通信、并支持多种编程语言开发客户端。
 
+该部分以HTTP预测服务部署为例，介绍怎样在PaddleClas中使用PaddleServing部署模型服务。
+
+
+## 二、Serving安装
+
+Serving官网推荐使用docker安装并部署Serving环境。首先需要拉取docker环境并创建基于Serving的docker。
+
+```shell
+nvidia-docker pull hub.baidubce.com/paddlepaddle/serving:0.2.0-gpu
+nvidia-docker run -p 9292:9292 --name test -dit hub.baidubce.com/paddlepaddle/serving:0.2.0-gpu
+nvidia-docker exec -it test bash
+```
+
+进入docker后，需要安装Serving相关的python包。
+
+```shell
+pip install paddlepaddle-gpu
+pip install paddle-serving-client
+pip install paddle-serving-server-gpu
+```
+
+* 如果安装速度太慢，可以通过`-i https://pypi.tuna.tsinghua.edu.cn/simple`更换源，加速安装过程。
+
+* 如果希望部署CPU服务，可以安装serving-server的cpu版本，安装命令如下。
+
+```shell
+pip install paddle-serving-server
+```
+
+### 三、导出模型
+
+使用`tools/export_serving_model.py`脚本导出Serving模型，以`ResNet50_vd`为例，使用方法如下。
+
+```shell
+python tools/export_serving_model.py -m ResNet50_vd -p ./pretrained/ResNet50_vd_pretrained/ -o serving
+```
+
+最终在serving文件夹下会生成`ppcls_client_conf`与`ppcls_model`两个文件夹，分别存储了client配置、模型参数与结构文件。
+
+
+### 四、服务部署与请求
+
+* 使用下面的方式启动Serving服务。
+
+```shell
+python tools/serving/image_service_gpu.py serving/ppcls_model workdir 9292
+```
+
+其中`serving/ppcls_model`为刚才保存的Serving模型地址，`workdir`为为工作目录，`9292`为服务的端口号。
+
+
+* 使用下面的脚本向Serving服务发送识别请求，并返回结果。
+
+```
+python tools/serving/image_http_client.py  9292 ./docs/images/logo.png
+```
+
+`9292`为发送请求的端口号，需要与服务启动时的端口号保持一致，`./docs/images/logo.png`为待识别的图像文件。最终返回Top1识别结果的类别ID以及概率值。
+
+* 更多的服务部署类型，如`RPC预测服务`等，可以参考Serving的github官网：[https://github.com/PaddlePaddle/Serving/tree/develop/python/examples/imagenet](https://github.com/PaddlePaddle/Serving/tree/develop/python/examples/imagenet)

tools/export_serving_model.py

+# Copyright (c) 2020 PaddlePaddle Authors. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import argparse
+import os
+from ppcls.modeling import architectures
+
+import paddle.fluid as fluid
+import paddle_serving_client.io as serving_io
+
+
+def parse_args():
+    parser = argparse.ArgumentParser()
+    parser.add_argument("-m", "--model", type=str)
+    parser.add_argument("-p", "--pretrained_model", type=str)
+    parser.add_argument("-o", "--output_path", type=str, default="")
+    parser.add_argument("--class_dim", type=int, default=1000)
+    parser.add_argument("--img_size", type=int, default=224)
+
+    return parser.parse_args()
+
+
+def create_input(img_size=224):
+    image = fluid.data(
+        name='image', shape=[None, 3, img_size, img_size], dtype='float32')
+    return image
+
+
+def create_model(args, model, input, class_dim=1000):
+    if args.model == "GoogLeNet":
+        out, _, _ = model.net(input=input, class_dim=class_dim)
+    else:
+        out = model.net(input=input, class_dim=class_dim)
+        out = fluid.layers.softmax(out)
+    return out
+
+
+def main():
+    args = parse_args()
+
+    model = architectures.__dict__[args.model]()
+
+    place = fluid.CPUPlace()
+    exe = fluid.Executor(place)
+
+    startup_prog = fluid.Program()
+    infer_prog = fluid.Program()
+
+    with fluid.program_guard(infer_prog, startup_prog):
+        with fluid.unique_name.guard():
+            image = create_input(args.img_size)
+            out = create_model(args, model, image, class_dim=args.class_dim)
+
+    infer_prog = infer_prog.clone(for_test=True)
+    fluid.load(
+        program=infer_prog, model_path=args.pretrained_model, executor=exe)
+
+    model_path = os.path.join(args.output_path, "ppcls_model")
+    conf_path = os.path.join(args.output_path, "ppcls_client_conf")
+    serving_io.save_model(model_path, conf_path, {"image": image},
+                          {"prediction": out}, infer_prog)
+
+
+if __name__ == "__main__":
+    main()

tools/serving/image_http_client.py

+# Copyright (c) 2020 PaddlePaddle Authors. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import requests
+import base64
+import json
+import sys
+import numpy as np
+
+py_version = sys.version_info[0]
+
+
+def predict(image_path, server):
+    if py_version == 2:
+        image = base64.b64encode(open(image_path).read())
+    else:
+        image = base64.b64encode(open(image_path, "rb").read()).decode("utf-8")
+    req = json.dumps({"feed": [{"image": image}], "fetch": ["prediction"]})
+    r = requests.post(
+        server, data=req, headers={"Content-Type": "application/json"})
+    try:
+        pred = r.json()["result"]["prediction"][0]
+        cls_id = np.argmax(pred)
+        score = pred[cls_id]
+        pred = {"cls_id": cls_id, "score": score}
+        return pred
+    except ValueError:
+        print(r.text)
+    return r
+
+
+if __name__ == "__main__":
+    server = "http://127.0.0.1:{}/image/prediction".format(sys.argv[1])
+    image_file = sys.argv[2]
+    while True:
+        res = predict(image_file, server)
+        print("res:", res)

tools/serving/image_service_cpu.py

+# Copyright (c) 2020 PaddlePaddle Authors. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import sys
+import base64
+from paddle_serving_server.web_service import WebService
+import utils
+
+
+class ImageService(WebService):
+    def __init__(self, name):
+        super(ImageService, self).__init__(name=name)
+        self.operators = self.create_operators()
+
+    def create_operators(self):
+        size = 224
+        img_mean = [0.485, 0.456, 0.406]
+        img_std = [0.229, 0.224, 0.225]
+        img_scale = 1.0 / 255.0
+        decode_op = utils.DecodeImage()
+        resize_op = utils.ResizeImage(resize_short=256)
+        crop_op = utils.CropImage(size=(size, size))
+        normalize_op = utils.NormalizeImage(
+            scale=img_scale, mean=img_mean, std=img_std)
+        totensor_op = utils.ToTensor()
+        return [decode_op, resize_op, crop_op, normalize_op, totensor_op]
+
+    def _process_image(self, data, ops):
+        for op in ops:
+            data = op(data)
+        return data
+
+    def preprocess(self, feed={}, fetch=[]):
+        feed_batch = []
+        for ins in feed:
+            if "image" not in ins:
+                raise ("feed data error!")
+            sample = base64.b64decode(ins["image"])
+            img = self._process_image(sample, self.operators)
+            feed_batch.append({"image": img})
+        return feed_batch, fetch
+
+
+image_service = ImageService(name="image")
+image_service.load_model_config(sys.argv[1])
+image_service.prepare_server(
+    workdir=sys.argv[2], port=int(sys.argv[3]), device="cpu")
+image_service.run_server()
+image_service.run_flask()

tools/serving/image_service_gpu.py

+# Copyright (c) 2020 PaddlePaddle Authors. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import sys
+import base64
+from paddle_serving_server_gpu.web_service import WebService
+
+import utils
+
+
+class ImageService(WebService):
+    def __init__(self, name):
+        super(ImageService, self).__init__(name=name)
+        self.operators = self.create_operators()
+
+    def create_operators(self):
+        size = 224
+        img_mean = [0.485, 0.456, 0.406]
+        img_std = [0.229, 0.224, 0.225]
+        img_scale = 1.0 / 255.0
+        decode_op = utils.DecodeImage()
+        resize_op = utils.ResizeImage(resize_short=256)
+        crop_op = utils.CropImage(size=(size, size))
+        normalize_op = utils.NormalizeImage(
+            scale=img_scale, mean=img_mean, std=img_std)
+        totensor_op = utils.ToTensor()
+        return [decode_op, resize_op, crop_op, normalize_op, totensor_op]
+
+    def _process_image(self, data, ops):
+        for op in ops:
+            data = op(data)
+        return data
+
+    def preprocess(self, feed={}, fetch=[]):
+        feed_batch = []
+        for ins in feed:
+            if "image" not in ins:
+                raise ("feed data error!")
+            sample = base64.b64decode(ins["image"])
+            img = self._process_image(sample, self.operators)
+            feed_batch.append({"image": img})
+        return feed_batch, fetch
+
+
+image_service = ImageService(name="image")
+image_service.load_model_config(sys.argv[1])
+image_service.set_gpus("0")
+image_service.prepare_server(
+    workdir=sys.argv[2], port=int(sys.argv[3]), device="gpu")
+image_service.run_server()
+image_service.run_flask()

tools/serving/utils.py

+# Copyright (c) 2020 PaddlePaddle Authors. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import cv2
+import numpy as np
+
+
+class DecodeImage(object):
+    def __init__(self, to_rgb=True):
+        self.to_rgb = to_rgb
+
+    def __call__(self, img):
+        data = np.frombuffer(img, dtype='uint8')
+        img = cv2.imdecode(data, 1)
+        if self.to_rgb:
+            assert img.shape[2] == 3, 'invalid shape of image[%s]' % (
+                img.shape)
+            img = img[:, :, ::-1]
+
+        return img
+
+
+class ResizeImage(object):
+    def __init__(self, resize_short=None):
+        self.resize_short = resize_short
+
+    def __call__(self, img):
+        img_h, img_w = img.shape[:2]
+        percent = float(self.resize_short) / min(img_w, img_h)
+        w = int(round(img_w * percent))
+        h = int(round(img_h * percent))
+        return cv2.resize(img, (w, h))
+
+
+class CropImage(object):
+    def __init__(self, size):
+        if type(size) is int:
+            self.size = (size, size)
+        else:
+            self.size = size
+
+    def __call__(self, img):
+        w, h = self.size
+        img_h, img_w = img.shape[:2]
+        w_start = (img_w - w) // 2
+        h_start = (img_h - h) // 2
+
+        w_end = w_start + w
+        h_end = h_start + h
+        return img[h_start:h_end, w_start:w_end, :]
+
+
+class NormalizeImage(object):
+    def __init__(self, scale=None, mean=None, std=None):
+        self.scale = np.float32(scale if scale is not None else 1.0 / 255.0)
+        mean = mean if mean is not None else [0.485, 0.456, 0.406]
+        std = std if std is not None else [0.229, 0.224, 0.225]
+
+        shape = (1, 1, 3)
+        self.mean = np.array(mean).reshape(shape).astype('float32')
+        self.std = np.array(std).reshape(shape).astype('float32')
+
+    def __call__(self, img):
+        return (img.astype('float32') * self.scale - self.mean) / self.std
+
+
+class ToTensor(object):
+    def __init__(self):
+        pass
+
+    def __call__(self, img):
+        img = img.transpose((2, 0, 1))
+        return img