[Model] Support PP-StructureV2-Layout model (#1867)

* [Model] init pp-structurev2-layout code

* [Model] init pp-structurev2-layout code

* [Model] init pp-structurev2-layout code

* [Model] add structurev2_layout_preprocessor

* [PP-StructureV2] add postprocessor and layout detector class

* [PP-StructureV2] add postprocessor and layout detector class

* [PP-StructureV2] add postprocessor and layout detector class

* [PP-StructureV2] add postprocessor and layout detector class

* [PP-StructureV2] add postprocessor and layout detector class

* [pybind] add pp-structurev2-layout model pybind

* [pybind] add pp-structurev2-layout model pybind

* [Bug Fix] fixed code style

* [examples] add pp-structurev2-layout c++ examples

* [PP-StructureV2] add python example and docs

* [benchmark] add pp-structurev2-layout benchmark support

fastdeploy/vision/ocr/ppocr/utils/softmax.cc

@@ -0,0 +1,48 @@
+// Copyright (c) 2022 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.
+
+#include "fastdeploy/vision/ocr/ppocr/utils/ocr_utils.h"
+
+namespace fastdeploy {
+namespace vision {
+namespace ocr {
+
+static inline float FastExp(float x) {
+  union { uint32_t i; float f; } v{}; 
+  v.i = (1 << 23) * (1.4426950409 * x + 126.93490512f);
+  return v.f;
+}
+
+std::vector<float> Softmax(std::vector<float> &src) {
+  int length = src.size();
+  std::vector<float> dst;
+  dst.resize(length);
+  const float alpha = static_cast<float>(
+    *std::max_element(&src[0], &src[0 + length]));
+  float denominator{0};
+
+  for (int i = 0; i < length; ++i) {
+    dst[i] = FastExp(src[i] - alpha);
+    denominator += dst[i];
+  }
+
+  for (int i = 0; i < length; ++i) {
+    dst[i] /= denominator;
+  }
+  return dst;
+}
+
+}  // namespace ocr
+}  // namespace vision
+}  // namespace fastdeploy