Merge pull request #15919 from heavengate/yolo_box

add yolo_box for detection box calc in YOLOv3

paddle/fluid/API.spec

@@ -331,6 +331,7 @@ paddle.fluid.layers.iou_similarity (ArgSpec(args=['x', 'y', 'name'], varargs=Non
 paddle.fluid.layers.box_coder (ArgSpec(args=['prior_box', 'prior_box_var', 'target_box', 'code_type', 'box_normalized', 'name', 'axis'], varargs=None, keywords=None, defaults=('encode_center_size', True, None, 0)), ('document', '032d0f4b7d8f6235ee5d91e473344f0e'))
 paddle.fluid.layers.polygon_box_transform (ArgSpec(args=['input', 'name'], varargs=None, keywords=None, defaults=(None,)), ('document', '0e5ac2507723a0b5adec473f9556799b'))
 paddle.fluid.layers.yolov3_loss (ArgSpec(args=['x', 'gtbox', 'gtlabel', 'anchors', 'anchor_mask', 'class_num', 'ignore_thresh', 'downsample_ratio', 'gtscore', 'use_label_smooth', 'name'], varargs=None, keywords=None, defaults=(None, True, None)), ('document', '57fa96922e42db8f064c3fb77f2255e8'))
+paddle.fluid.layers.yolo_box (ArgSpec(args=['x', 'img_size', 'anchors', 'class_num', 'conf_thresh', 'downsample_ratio', 'name'], varargs=None, keywords=None, defaults=(None,)), ('document', '5566169a5ab993d177792c023c7fb340'))
 paddle.fluid.layers.box_clip (ArgSpec(args=['input', 'im_info', 'name'], varargs=None, keywords=None, defaults=(None,)), ('document', '397e9e02b451d99c56e20f268fa03f2e'))
 paddle.fluid.layers.multiclass_nms (ArgSpec(args=['bboxes', 'scores', 'score_threshold', 'nms_top_k', 'keep_top_k', 'nms_threshold', 'normalized', 'nms_eta', 'background_label', 'name'], varargs=None, keywords=None, defaults=(0.3, True, 1.0, 0, None)), ('document', 'ca7d1107b6c5d2d6d8221039a220fde0'))
 paddle.fluid.layers.distribute_fpn_proposals (ArgSpec(args=['fpn_rois', 'min_level', 'max_level', 'refer_level', 'refer_scale', 'name'], varargs=None, keywords=None, defaults=(None,)), ('document', '7bb011ec26bace2bc23235aa4a17647d'))

paddle/fluid/operators/detection/CMakeLists.txt

@@ -33,6 +33,7 @@ detection_library(rpn_target_assign_op SRCS rpn_target_assign_op.cc)
 detection_library(generate_proposal_labels_op SRCS generate_proposal_labels_op.cc)
 detection_library(box_clip_op SRCS box_clip_op.cc box_clip_op.cu)
 detection_library(yolov3_loss_op SRCS yolov3_loss_op.cc)
+detection_library(yolo_box_op SRCS yolo_box_op.cc yolo_box_op.cu)
 detection_library(box_decoder_and_assign_op SRCS box_decoder_and_assign_op.cc box_decoder_and_assign_op.cu)
 
 if(WITH_GPU)

paddle/fluid/operators/detection/yolo_box_op.cc

+/* Copyright (c) 2019 PaddlePaddle Authors. All Rights Reserve.
+   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 "paddle/fluid/operators/detection/yolo_box_op.h"
+#include "paddle/fluid/framework/op_registry.h"
+
+namespace paddle {
+namespace operators {
+
+using framework::Tensor;
+
+class YoloBoxOp : public framework::OperatorWithKernel {
+ public:
+  using framework::OperatorWithKernel::OperatorWithKernel;
+  void InferShape(framework::InferShapeContext* ctx) const override {
+    PADDLE_ENFORCE(ctx->HasInput("X"),
+                   "Input(X) of YoloBoxOp should not be null.");
+    PADDLE_ENFORCE(ctx->HasInput("ImgSize"),
+                   "Input(ImgSize) of YoloBoxOp should not be null.");
+    PADDLE_ENFORCE(ctx->HasOutput("Boxes"),
+                   "Output(Boxes) of YoloBoxOp should not be null.");
+    PADDLE_ENFORCE(ctx->HasOutput("Scores"),
+                   "Output(Scores) of YoloBoxOp should not be null.");
+
+    auto dim_x = ctx->GetInputDim("X");
+    auto dim_imgsize = ctx->GetInputDim("ImgSize");
+    auto anchors = ctx->Attrs().Get<std::vector<int>>("anchors");
+    int anchor_num = anchors.size() / 2;
+    auto class_num = ctx->Attrs().Get<int>("class_num");
+
+    PADDLE_ENFORCE_EQ(dim_x.size(), 4, "Input(X) should be a 4-D tensor.");
+    PADDLE_ENFORCE_EQ(
+        dim_x[1], anchor_num * (5 + class_num),
+        "Input(X) dim[1] should be equal to (anchor_mask_number * (5 "
+        "+ class_num)).");
+    PADDLE_ENFORCE_EQ(dim_imgsize.size(), 2,
+                      "Input(ImgSize) should be a 2-D tensor.");
+    PADDLE_ENFORCE_EQ(
+        dim_imgsize[0], dim_x[0],
+        "Input(ImgSize) dim[0] and Input(X) dim[0] should be same.");
+    PADDLE_ENFORCE_EQ(dim_imgsize[1], 2, "Input(ImgSize) dim[1] should be 2.");
+    PADDLE_ENFORCE_GT(anchors.size(), 0,
+                      "Attr(anchors) length should be greater than 0.");
+    PADDLE_ENFORCE_EQ(anchors.size() % 2, 0,
+                      "Attr(anchors) length should be even integer.");
+    PADDLE_ENFORCE_GT(class_num, 0,
+                      "Attr(class_num) should be an integer greater than 0.");
+
+    int box_num = dim_x[2] * dim_x[3] * anchor_num;
+    std::vector<int64_t> dim_boxes({dim_x[0], box_num, 4});
+    ctx->SetOutputDim("Boxes", framework::make_ddim(dim_boxes));
+
+    std::vector<int64_t> dim_scores({dim_x[0], box_num, class_num});
+    ctx->SetOutputDim("Scores", framework::make_ddim(dim_scores));
+  }
+
+ protected:
+  framework::OpKernelType GetExpectedKernelType(
+      const framework::ExecutionContext& ctx) const override {
+    return framework::OpKernelType(ctx.Input<Tensor>("X")->type(),
+                                   ctx.GetPlace());
+  }
+};
+
+class YoloBoxOpMaker : public framework::OpProtoAndCheckerMaker {
+ public:
+  void Make() override {
+    AddInput("X",
+             "The input tensor of YoloBox operator is a 4-D tensor with "
+             "shape of [N, C, H, W]. The second dimension(C) stores "
+             "box locations, confidence score and classification one-hot "
+             "keys of each anchor box. Generally, X should be the output "
+             "of YOLOv3 network.");
+    AddInput("ImgSize",
+             "The image size tensor of YoloBox operator, "
+             "This is a 2-D tensor with shape of [N, 2]. This tensor holds "
+             "height and width of each input image used for resizing output "
+             "box in input image scale.");
+    AddOutput("Boxes",
+              "The output tensor of detection boxes of YoloBox operator, "
+              "This is a 3-D tensor with shape of [N, M, 4], N is the "
+              "batch num, M is output box number, and the 3rd dimension "
+              "stores [xmin, ymin, xmax, ymax] coordinates of boxes.");
+    AddOutput("Scores",
+              "The output tensor of detection boxes scores of YoloBox "
+              "operator, This is a 3-D tensor with shape of "
+              "[N, M, :attr:`class_num`], N is the batch num, M is "
+              "output box number.");
+
+    AddAttr<int>("class_num", "The number of classes to predict.");
+    AddAttr<std::vector<int>>("anchors",
+                              "The anchor width and height, "
+                              "it will be parsed pair by pair.")
+        .SetDefault(std::vector<int>{});
+    AddAttr<int>("downsample_ratio",
+                 "The downsample ratio from network input to YoloBox operator "
+                 "input, so 32, 16, 8 should be set for the first, second, "
+                 "and thrid YoloBox operators.")
+        .SetDefault(32);
+    AddAttr<float>("conf_thresh",
+                   "The confidence scores threshold of detection boxes. "
+                   "Boxes with confidence scores under threshold should "
+                   "be ignored.")
+        .SetDefault(0.01);
+    AddComment(R"DOC(
+         This operator generates YOLO detection boxes from output of YOLOv3 network.
+         
+         The output of previous network is in shape [N, C, H, W], while H and W
+         should be the same, H and W specify the grid size, each grid point predict 
+         given number boxes, this given number, which following will be represented as S,
+         is specified by the number of anchors. In the second dimension(the channel
+         dimension), C should be equal to S * (5 + class_num), class_num is the object 
+         category number of source dataset(such as 80 in coco dataset), so the 
+         second(channel) dimension, apart from 4 box location coordinates x, y, w, h, 
+         also includes confidence score of the box and class one-hot key of each anchor 
+         box.
+
+         Assume the 4 location coordinates are :math:`t_x, t_y, t_w, t_h`, the box 
+         predictions should be as follows:
+
+         $$
+         b_x = \\sigma(t_x) + c_x
+         $$
+         $$
+         b_y = \\sigma(t_y) + c_y
+         $$
+         $$
+         b_w = p_w e^{t_w}
+         $$
+         $$
+         b_h = p_h e^{t_h}
+         $$
+
+         in the equation above, :math:`c_x, c_y` is the left top corner of current grid
+         and :math:`p_w, p_h` is specified by anchors.
+
+         The logistic regression value of the 5th channel of each anchor prediction boxes
+         represents the confidence score of each prediction box, and the logistic
+         regression value of the last :attr:`class_num` channels of each anchor prediction 
+         boxes represents the classifcation scores. Boxes with confidence scores less than
+         :attr:`conf_thresh` should be ignored, and box final scores is the product of 
+         confidence scores and classification scores.
+
+         $$
+         score_{pred} = score_{conf} * score_{class}
+         $$
+
+         )DOC");
+  }
+};
+
+}  // namespace operators
+}  // namespace paddle
+
+namespace ops = paddle::operators;
+REGISTER_OPERATOR(yolo_box, ops::YoloBoxOp, ops::YoloBoxOpMaker,
+                  paddle::framework::EmptyGradOpMaker);
+REGISTER_OP_CPU_KERNEL(yolo_box, ops::YoloBoxKernel<float>,
+                       ops::YoloBoxKernel<double>);

paddle/fluid/operators/detection/yolo_box_op.cu

+/* Copyright (c) 2019 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 "paddle/fluid/operators/detection/yolo_box_op.h"
+#include "paddle/fluid/operators/math/math_function.h"
+
+namespace paddle {
+namespace operators {
+
+using Tensor = framework::Tensor;
+
+template <typename T>
+__global__ void KeYoloBoxFw(const T* input, const int* imgsize, T* boxes,
+                            T* scores, const float conf_thresh,
+                            const int* anchors, const int n, const int h,
+                            const int w, const int an_num, const int class_num,
+                            const int box_num, int input_size) {
+  int tid = blockIdx.x * blockDim.x + threadIdx.x;
+  int stride = blockDim.x * gridDim.x;
+  T box[4];
+  for (; tid < n * box_num; tid += stride) {
+    int grid_num = h * w;
+    int i = tid / box_num;
+    int j = (tid % box_num) / grid_num;
+    int k = (tid % grid_num) / w;
+    int l = tid % w;
+
+    int an_stride = (5 + class_num) * grid_num;
+    int img_height = imgsize[2 * i];
+    int img_width = imgsize[2 * i + 1];
+
+    int obj_idx =
+        GetEntryIndex(i, j, k * w + l, an_num, an_stride, grid_num, 4);
+    T conf = sigmoid<T>(input[obj_idx]);
+    if (conf < conf_thresh) {
+      continue;
+    }
+
+    int box_idx =
+        GetEntryIndex(i, j, k * w + l, an_num, an_stride, grid_num, 0);
+    GetYoloBox<T>(box, input, anchors, l, k, j, h, input_size, box_idx,
+                  grid_num, img_height, img_width);
+    box_idx = (i * box_num + j * grid_num + k * w + l) * 4;
+    CalcDetectionBox<T>(boxes, box, box_idx, img_height, img_width);
+
+    int label_idx =
+        GetEntryIndex(i, j, k * w + l, an_num, an_stride, grid_num, 5);
+    int score_idx = (i * box_num + j * grid_num + k * w + l) * class_num;
+    CalcLabelScore<T>(scores, input, label_idx, score_idx, class_num, conf,
+                      grid_num);
+  }
+}
+
+template <typename T>
+class YoloBoxOpCUDAKernel : public framework::OpKernel<T> {
+ public:
+  void Compute(const framework::ExecutionContext& ctx) const override {
+    auto* input = ctx.Input<Tensor>("X");
+    auto* img_size = ctx.Input<Tensor>("ImgSize");
+    auto* boxes = ctx.Output<Tensor>("Boxes");
+    auto* scores = ctx.Output<Tensor>("Scores");
+
+    auto anchors = ctx.Attr<std::vector<int>>("anchors");
+    int class_num = ctx.Attr<int>("class_num");
+    float conf_thresh = ctx.Attr<float>("conf_thresh");
+    int downsample_ratio = ctx.Attr<int>("downsample_ratio");
+
+    const int n = input->dims()[0];
+    const int h = input->dims()[2];
+    const int w = input->dims()[3];
+    const int box_num = boxes->dims()[1];
+    const int an_num = anchors.size() / 2;
+    int input_size = downsample_ratio * h;
+
+    auto& dev_ctx = ctx.cuda_device_context();
+    auto& allocator =
+        platform::DeviceTemporaryAllocator::Instance().Get(dev_ctx);
+    int bytes = sizeof(int) * anchors.size();
+    auto anchors_ptr = allocator.Allocate(sizeof(int) * anchors.size());
+    int* anchors_data = reinterpret_cast<int*>(anchors_ptr->ptr());
+    const auto gplace = boost::get<platform::CUDAPlace>(ctx.GetPlace());
+    const auto cplace = platform::CPUPlace();
+    memory::Copy(gplace, anchors_data, cplace, anchors.data(), bytes,
+                 dev_ctx.stream());
+
+    const T* input_data = input->data<T>();
+    const int* imgsize_data = img_size->data<int>();
+    T* boxes_data = boxes->mutable_data<T>({n, box_num, 4}, ctx.GetPlace());
+    T* scores_data =
+        scores->mutable_data<T>({n, box_num, class_num}, ctx.GetPlace());
+    math::SetConstant<platform::CUDADeviceContext, T> set_zero;
+    set_zero(dev_ctx, boxes, static_cast<T>(0));
+    set_zero(dev_ctx, scores, static_cast<T>(0));
+
+    int grid_dim = (n * box_num + 512 - 1) / 512;
+    grid_dim = grid_dim > 8 ? 8 : grid_dim;
+
+    KeYoloBoxFw<T><<<grid_dim, 512, 0, ctx.cuda_device_context().stream()>>>(
+        input_data, imgsize_data, boxes_data, scores_data, conf_thresh,
+        anchors_data, n, h, w, an_num, class_num, box_num, input_size);
+  }
+};
+
+}  // namespace operators
+}  // namespace paddle
+
+namespace ops = paddle::operators;
+REGISTER_OP_CUDA_KERNEL(yolo_box, ops::YoloBoxOpCUDAKernel<float>,
+                        ops::YoloBoxOpCUDAKernel<double>);

paddle/fluid/operators/detection/yolo_box_op.h

+/* Copyright (c) 2019 PaddlePaddle Authors. All Rights Reserve.
+   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. */
+
+#pragma once
+#include <algorithm>
+#include <vector>
+#include "paddle/fluid/framework/op_registry.h"
+#include "paddle/fluid/platform/hostdevice.h"
+
+namespace paddle {
+namespace operators {
+
+using Tensor = framework::Tensor;
+
+template <typename T>
+HOSTDEVICE inline T sigmoid(T x) {
+  return 1.0 / (1.0 + std::exp(-x));
+}
+
+template <typename T>
+HOSTDEVICE inline void GetYoloBox(T* box, const T* x, const int* anchors, int i,
+                                  int j, int an_idx, int grid_size,
+                                  int input_size, int index, int stride,
+                                  int img_height, int img_width) {
+  box[0] = (i + sigmoid<T>(x[index])) * img_width / grid_size;
+  box[1] = (j + sigmoid<T>(x[index + stride])) * img_height / grid_size;
+  box[2] = std::exp(x[index + 2 * stride]) * anchors[2 * an_idx] * img_width /
+           input_size;
+  box[3] = std::exp(x[index + 3 * stride]) * anchors[2 * an_idx + 1] *
+           img_height / input_size;
+}
+
+HOSTDEVICE inline int GetEntryIndex(int batch, int an_idx, int hw_idx,
+                                    int an_num, int an_stride, int stride,
+                                    int entry) {
+  return (batch * an_num + an_idx) * an_stride + entry * stride + hw_idx;
+}
+
+template <typename T>
+HOSTDEVICE inline void CalcDetectionBox(T* boxes, T* box, const int box_idx,
+                                        const int img_height,
+                                        const int img_width) {
+  boxes[box_idx] = box[0] - box[2] / 2;
+  boxes[box_idx + 1] = box[1] - box[3] / 2;
+  boxes[box_idx + 2] = box[0] + box[2] / 2;
+  boxes[box_idx + 3] = box[1] + box[3] / 2;
+
+  boxes[box_idx] = boxes[box_idx] > 0 ? boxes[box_idx] : static_cast<T>(0);
+  boxes[box_idx + 1] =
+      boxes[box_idx + 1] > 0 ? boxes[box_idx + 1] : static_cast<T>(0);
+  boxes[box_idx + 2] = boxes[box_idx + 2] < img_width - 1
+                           ? boxes[box_idx + 2]
+                           : static_cast<T>(img_width - 1);
+  boxes[box_idx + 3] = boxes[box_idx + 3] < img_height - 1
+                           ? boxes[box_idx + 3]
+                           : static_cast<T>(img_height - 1);
+}
+
+template <typename T>
+HOSTDEVICE inline void CalcLabelScore(T* scores, const T* input,
+                                      const int label_idx, const int score_idx,
+                                      const int class_num, const T conf,
+                                      const int stride) {
+  for (int i = 0; i < class_num; i++) {
+    scores[score_idx + i] = conf * sigmoid<T>(input[label_idx + i * stride]);
+  }
+}
+
+template <typename T>
+class YoloBoxKernel : public framework::OpKernel<T> {
+ public:
+  void Compute(const framework::ExecutionContext& ctx) const override {
+    auto* input = ctx.Input<Tensor>("X");
+    auto* imgsize = ctx.Input<Tensor>("ImgSize");
+    auto* boxes = ctx.Output<Tensor>("Boxes");
+    auto* scores = ctx.Output<Tensor>("Scores");
+    auto anchors = ctx.Attr<std::vector<int>>("anchors");
+    int class_num = ctx.Attr<int>("class_num");
+    float conf_thresh = ctx.Attr<float>("conf_thresh");
+    int downsample_ratio = ctx.Attr<int>("downsample_ratio");
+
+    const int n = input->dims()[0];
+    const int h = input->dims()[2];
+    const int w = input->dims()[3];
+    const int box_num = boxes->dims()[1];
+    const int an_num = anchors.size() / 2;
+    int input_size = downsample_ratio * h;
+
+    const int stride = h * w;
+    const int an_stride = (class_num + 5) * stride;
+
+    Tensor anchors_;
+    auto anchors_data =
+        anchors_.mutable_data<int>({an_num * 2}, ctx.GetPlace());
+    std::copy(anchors.begin(), anchors.end(), anchors_data);
+
+    const T* input_data = input->data<T>();
+    const int* imgsize_data = imgsize->data<int>();
+    T* boxes_data = boxes->mutable_data<T>({n, box_num, 4}, ctx.GetPlace());
+    memset(boxes_data, 0, boxes->numel() * sizeof(T));
+    T* scores_data =
+        scores->mutable_data<T>({n, box_num, class_num}, ctx.GetPlace());
+    memset(scores_data, 0, scores->numel() * sizeof(T));
+
+    T box[4];
+    for (int i = 0; i < n; i++) {
+      int img_height = imgsize_data[2 * i];
+      int img_width = imgsize_data[2 * i + 1];
+
+      for (int j = 0; j < an_num; j++) {
+        for (int k = 0; k < h; k++) {
+          for (int l = 0; l < w; l++) {
+            int obj_idx =
+                GetEntryIndex(i, j, k * w + l, an_num, an_stride, stride, 4);
+            T conf = sigmoid<T>(input_data[obj_idx]);
+            if (conf < conf_thresh) {
+              continue;
+            }
+
+            int box_idx =
+                GetEntryIndex(i, j, k * w + l, an_num, an_stride, stride, 0);
+            GetYoloBox<T>(box, input_data, anchors_data, l, k, j, h, input_size,
+                          box_idx, stride, img_height, img_width);
+            box_idx = (i * box_num + j * stride + k * w + l) * 4;
+            CalcDetectionBox<T>(boxes_data, box, box_idx, img_height,
+                                img_width);
+
+            int label_idx =
+                GetEntryIndex(i, j, k * w + l, an_num, an_stride, stride, 5);
+            int score_idx = (i * box_num + j * stride + k * w + l) * class_num;
+            CalcLabelScore<T>(scores_data, input_data, label_idx, score_idx,
+                              class_num, conf, stride);
+          }
+        }
+      }
+    }
+  }
+};
+
+}  // namespace operators
+}  // namespace paddle

python/paddle/fluid/layers/detection.py

@@ -49,6 +49,7 @@ __all__ = [
     'box_coder',
     'polygon_box_transform',
     'yolov3_loss',
+    'yolo_box',
     'box_clip',
     'multiclass_nms',
     'distribute_fpn_proposals',
@@ -628,6 +629,83 @@ def yolov3_loss(x,
     return loss
 
 
+@templatedoc(op_type="yolo_box")
+def yolo_box(x,
+             img_size,
+             anchors,
+             class_num,
+             conf_thresh,
+             downsample_ratio,
+             name=None):
+    """
+    ${comment}
+
+    Args:
+        x (Variable): ${x_comment}
+        img_size (Variable): ${img_size_comment}
+        anchors (list|tuple): ${anchors_comment}
+        class_num (int): ${class_num_comment}
+        conf_thresh (float): ${conf_thresh_comment}
+        downsample_ratio (int): ${downsample_ratio_comment}
+        name (string): the name of yolo box layer. Default None.
+
+    Returns:
+        Variable: A 3-D tensor with shape [N, M, 4], the coordinates of boxes,
+        and a 3-D tensor with shape [N, M, :attr:`class_num`], the classification 
+        scores of boxes.
+
+    Raises:
+        TypeError: Input x of yolov_box must be Variable
+        TypeError: Attr anchors of yolo box must be list or tuple
+        TypeError: Attr class_num of yolo box must be an integer
+        TypeError: Attr conf_thresh of yolo box must be a float number
+
+    Examples:
+
+    .. code-block:: python
+
+        x = fluid.layers.data(name='x', shape=[255, 13, 13], dtype='float32')
+        anchors = [10, 13, 16, 30, 33, 23]
+        loss = fluid.layers.yolo_box(x=x, class_num=80, anchors=anchors, 
+                                        conf_thresh=0.01, downsample_ratio=32)
+    """
+    helper = LayerHelper('yolo_box', **locals())
+
+    if not isinstance(x, Variable):
+        raise TypeError("Input x of yolo_box must be Variable")
+    if not isinstance(img_size, Variable):
+        raise TypeError("Input img_size of yolo_box must be Variable")
+    if not isinstance(anchors, list) and not isinstance(anchors, tuple):
+        raise TypeError("Attr anchors of yolo_box must be list or tuple")
+    if not isinstance(class_num, int):
+        raise TypeError("Attr class_num of yolo_box must be an integer")
+    if not isinstance(conf_thresh, float):
+        raise TypeError("Attr ignore_thresh of yolo_box must be a float number")
+
+    boxes = helper.create_variable_for_type_inference(dtype=x.dtype)
+    scores = helper.create_variable_for_type_inference(dtype=x.dtype)
+
+    attrs = {
+        "anchors": anchors,
+        "class_num": class_num,
+        "conf_thresh": conf_thresh,
+        "downsample_ratio": downsample_ratio,
+    }
+
+    helper.append_op(
+        type='yolo_box',
+        inputs={
+            "X": x,
+            "ImgSize": img_size,
+        },
+        outputs={
+            'Boxes': boxes,
+            'Scores': scores,
+        },
+        attrs=attrs)
+    return boxes, scores
+
+
 @templatedoc()
 def detection_map(detect_res,
                   label,

python/paddle/fluid/tests/test_detection.py

@@ -489,6 +489,16 @@ class TestYoloDetection(unittest.TestCase):
 
             self.assertIsNotNone(loss)
 
+    def test_yolo_box(self):
+        program = Program()
+        with program_guard(program):
+            x = layers.data(name='x', shape=[30, 7, 7], dtype='float32')
+            img_size = layers.data(name='img_size', shape=[2], dtype='int32')
+            boxes, scores = layers.yolo_box(x, img_size, [10, 13, 30, 13], 10,
+                                            0.01, 32)
+            self.assertIsNotNone(boxes)
+            self.assertIsNotNone(scores)
+
 
 class TestBoxClip(unittest.TestCase):
     def test_box_clip(self):

python/paddle/fluid/tests/unittests/test_yolo_box_op.py

+#   Copyright (c) 2019 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.
+
+from __future__ import division
+
+import unittest
+import numpy as np
+from op_test import OpTest
+
+from paddle.fluid import core
+
+
+def sigmoid(x):
+    return 1.0 / (1.0 + np.exp(-1.0 * x))
+
+
+def YoloBox(x, img_size, attrs):
+    n, c, h, w = x.shape
+    anchors = attrs['anchors']
+    an_num = int(len(anchors) // 2)
+    class_num = attrs['class_num']
+    conf_thresh = attrs['conf_thresh']
+    downsample = attrs['downsample']
+    input_size = downsample * h
+
+    x = x.reshape((n, an_num, 5 + class_num, h, w)).transpose((0, 1, 3, 4, 2))
+
+    pred_box = x[:, :, :, :, :4].copy()
+    grid_x = np.tile(np.arange(w).reshape((1, w)), (h, 1))
+    grid_y = np.tile(np.arange(h).reshape((h, 1)), (1, w))
+    pred_box[:, :, :, :, 0] = (grid_x + sigmoid(pred_box[:, :, :, :, 0])) / w
+    pred_box[:, :, :, :, 1] = (grid_y + sigmoid(pred_box[:, :, :, :, 1])) / h
+
+    anchors = [(anchors[i], anchors[i + 1]) for i in range(0, len(anchors), 2)]
+    anchors_s = np.array(
+        [(an_w / input_size, an_h / input_size) for an_w, an_h in anchors])
+    anchor_w = anchors_s[:, 0:1].reshape((1, an_num, 1, 1))
+    anchor_h = anchors_s[:, 1:2].reshape((1, an_num, 1, 1))
+    pred_box[:, :, :, :, 2] = np.exp(pred_box[:, :, :, :, 2]) * anchor_w
+    pred_box[:, :, :, :, 3] = np.exp(pred_box[:, :, :, :, 3]) * anchor_h
+
+    pred_conf = sigmoid(x[:, :, :, :, 4:5])
+    pred_conf[pred_conf < conf_thresh] = 0.
+    pred_score = sigmoid(x[:, :, :, :, 5:]) * pred_conf
+    pred_box = pred_box * (pred_conf > 0.).astype('float32')
+
+    pred_box = pred_box.reshape((n, -1, 4))
+    pred_box[:, :, :2], pred_box[:, :, 2:4] = \
+        pred_box[:, :, :2] - pred_box[:, :, 2:4] / 2., \
+        pred_box[:, :, :2] + pred_box[:, :, 2:4] / 2.0
+    pred_box[:, :, 0] = pred_box[:, :, 0] * img_size[:, 1][:, np.newaxis]
+    pred_box[:, :, 1] = pred_box[:, :, 1] * img_size[:, 0][:, np.newaxis]
+    pred_box[:, :, 2] = pred_box[:, :, 2] * img_size[:, 1][:, np.newaxis]
+    pred_box[:, :, 3] = pred_box[:, :, 3] * img_size[:, 0][:, np.newaxis]
+
+    for i in range(len(pred_box)):
+        pred_box[i, :, 0] = np.clip(pred_box[i, :, 0], 0, np.inf)
+        pred_box[i, :, 1] = np.clip(pred_box[i, :, 1], 0, np.inf)
+        pred_box[i, :, 2] = np.clip(pred_box[i, :, 2], -np.inf,
+                                    img_size[i, 1] - 1)
+        pred_box[i, :, 3] = np.clip(pred_box[i, :, 3], -np.inf,
+                                    img_size[i, 0] - 1)
+
+    return pred_box, pred_score.reshape((n, -1, class_num))
+
+
+class TestYoloBoxOp(OpTest):
+    def setUp(self):
+        self.initTestCase()
+        self.op_type = 'yolo_box'
+        x = np.random.random(self.x_shape).astype('float32')
+        img_size = np.random.randint(10, 20, self.imgsize_shape).astype('int32')
+
+        self.attrs = {
+            "anchors": self.anchors,
+            "class_num": self.class_num,
+            "conf_thresh": self.conf_thresh,
+            "downsample": self.downsample,
+        }
+
+        self.inputs = {
+            'X': x,
+            'ImgSize': img_size,
+        }
+        boxes, scores = YoloBox(x, img_size, self.attrs)
+        self.outputs = {
+            "Boxes": boxes,
+            "Scores": scores,
+        }
+
+    def test_check_output(self):
+        self.check_output()
+
+    def initTestCase(self):
+        self.anchors = [10, 13, 16, 30, 33, 23]
+        an_num = int(len(self.anchors) // 2)
+        self.batch_size = 32
+        self.class_num = 2
+        self.conf_thresh = 0.5
+        self.downsample = 32
+        self.x_shape = (self.batch_size, an_num * (5 + self.class_num), 13, 13)
+        self.imgsize_shape = (self.batch_size, 2)
+
+
+if __name__ == "__main__":
+    unittest.main()