text: # 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 paddle
  import paddle.fluid as fluid
  
  
  class DetectionOutput(object):
      def __init__(self, nms_threshold, nms_top_k, keep_top_k, nms_eta,
                   score_threshold, background_label):
          self.detection_output_layer_attrs = {
              "background_label": background_label,
              "nms_threshold": nms_threshold,
              "nms_top_k": nms_top_k,
              "keep_top_k": keep_top_k,
              "score_threshold": score_threshold,
              "nms_eta": nms_eta
          }
  
      def __call__(self, x0, x1, x2):
          priorbox_list = paddle.split(x2, num_or_sections=2, axis=1)
          pb = priorbox_list[0]
          pbv = priorbox_list[1]
          pb = paddle.reshape(x=pb, shape=[-1, 4])
          pbv = paddle.reshape(x=pbv, shape=[-1, 4])
          pb_dim = fluid.layers.shape(pb)[0]
          loc = paddle.reshape(x0, shape=[-1, pb_dim, 4])
          conf_flatten = paddle.reshape(x1, shape=[0, pb_dim, -1])
          out = fluid.layers.detection_output(
              loc=loc,
              scores=conf_flatten,
              prior_box=pb,
              prior_box_var=pbv,
              **self.detection_output_layer_attrs)
          return out
  