Faster-RCNN models support

modules/dnn/include/opencv2/dnn/all_layers.hpp

@@ -74,7 +74,7 @@ CV__DNN_EXPERIMENTAL_NS_BEGIN
     class CV_EXPORTS BlankLayer : public Layer
     {
     public:
-        static Ptr<BlankLayer> create(const LayerParams &params);
+        static Ptr<Layer> create(const LayerParams &params);
     };
 
     //! LSTM recurrent layer
@@ -567,6 +567,12 @@ CV__DNN_EXPERIMENTAL_NS_BEGIN
         static Ptr<ResizeNearestNeighborLayer> create(const LayerParams& params);
     };
 
+    class CV_EXPORTS ProposalLayer : public Layer
+    {
+    public:
+        static Ptr<ProposalLayer> create(const LayerParams& params);
+    };
+
 //! @}
 //! @}
 CV__DNN_EXPERIMENTAL_NS_END

modules/dnn/src/caffe/opencv-caffe.proto

@@ -547,6 +547,7 @@ message LayerParameter {
   optional PowerParameter power_param = 122;
   optional PReLUParameter prelu_param = 131;
   optional PriorBoxParameter prior_box_param = 150;
+  optional ProposalParameter proposal_param = 201;
   optional PythonParameter python_param = 130;
   optional RecurrentParameter recurrent_param = 146;
   optional ReductionParameter reduction_param = 136;
@@ -854,6 +855,9 @@ message SaveOutputParameter {
 
 message DropoutParameter {
   optional float dropout_ratio = 1 [default = 0.5]; // dropout ratio
+  // Faster-RCNN framework's parameter.
+  // source: https://github.com/rbgirshick/caffe-fast-rcnn/tree/faster-rcnn
+  optional bool scale_train = 2 [default = true];  // scale train or test phase
 }
 
 // DummyDataLayer fills any number of arbitrarily shaped blobs with random
@@ -1618,3 +1622,14 @@ message ROIPoolingParameter {
   // input scale to the scale used when pooling
   optional float spatial_scale = 3 [default = 1];
 }
+
+message ProposalParameter {
+  optional uint32 feat_stride = 1 [default = 16];
+  optional uint32 base_size = 2 [default = 16];
+  optional uint32 min_size = 3 [default = 16];
+  repeated float ratio = 4;
+  repeated float scale = 5;
+  optional uint32 pre_nms_topn = 6 [default = 6000];
+  optional uint32 post_nms_topn = 7 [default = 300];
+  optional float nms_thresh = 8 [default = 0.7];
+}

modules/dnn/src/init.cpp

@@ -122,6 +122,7 @@ void initializeLayerFactory()
     CV_DNN_REGISTER_LAYER_CLASS(Normalize,      NormalizeBBoxLayer);
     CV_DNN_REGISTER_LAYER_CLASS(Shift,          ShiftLayer);
     CV_DNN_REGISTER_LAYER_CLASS(Padding,        PaddingLayer);
+    CV_DNN_REGISTER_LAYER_CLASS(Proposal,       ProposalLayer);
     CV_DNN_REGISTER_LAYER_CLASS(Scale,          ScaleLayer);
 
     CV_DNN_REGISTER_LAYER_CLASS(LSTM,           LSTMLayer);

modules/dnn/src/layers/blank_layer.cpp

@@ -92,9 +92,25 @@ public:
     }
 };
 
-Ptr<BlankLayer> BlankLayer::create(const LayerParams& params)
+Ptr<Layer> BlankLayer::create(const LayerParams& params)
 {
-    return Ptr<BlankLayer>(new BlankLayerImpl(params));
+    // In case of Caffe's Dropout layer from Faster-RCNN framework,
+    // https://github.com/rbgirshick/caffe-fast-rcnn/tree/faster-rcnn
+    // return Power layer.
+    if (!params.get<bool>("scale_train", true))
+    {
+        float scale = 1 - params.get<float>("dropout_ratio", 0.5f);
+        CV_Assert(scale > 0);
+
+        LayerParams powerParams;
+        powerParams.name = params.name;
+        powerParams.type = "Power";
+        powerParams.set("scale", scale);
+
+        return PowerLayer::create(powerParams);
+    }
+    else
+        return Ptr<BlankLayer>(new BlankLayerImpl(params));
 }
 
 }

modules/dnn/src/layers/pooling_layer.cpp

@@ -88,6 +88,7 @@ public:
         else if (params.has("pooled_w") || params.has("pooled_h") || params.has("spatial_scale"))
         {
             type = ROI;
+            computeMaxIdx = false;
         }
         setParamsFrom(params);
         ceilMode = params.get<bool>("ceil_mode", true);
@@ -294,24 +295,17 @@ public:
                 int ystart, yend;
 
                 const float *srcData;
-                int xstartROI = 0;
-                float roiRatio = 0;
                 if (poolingType == ROI)
                 {
                     const float *roisData = rois->ptr<float>(n);
                     int ystartROI = scaleAndRoundRoi(roisData[2], spatialScale);
                     int yendROI = scaleAndRoundRoi(roisData[4], spatialScale);
                     int roiHeight = std::max(yendROI - ystartROI + 1, 1);
-                    roiRatio = (float)roiHeight / height;
+                    float roiRatio = (float)roiHeight / height;
 
                     ystart = ystartROI + y0 * roiRatio;
                     yend = ystartROI + std::ceil((y0 + 1) * roiRatio);
 
-                    xstartROI = scaleAndRoundRoi(roisData[1], spatialScale);
-                    int xendROI = scaleAndRoundRoi(roisData[3], spatialScale);
-                    int roiWidth = std::max(xendROI - xstartROI + 1, 1);
-                    roiRatio = (float)roiWidth / width;
-
                     CV_Assert(roisData[0] < src->size[0]);
                     srcData = src->ptr<float>(roisData[0], c);
                 }
@@ -331,22 +325,12 @@ public:
                 ofs0 += delta;
                 int x1 = x0 + delta;
 
-                if( poolingType == MAX || poolingType == ROI)
+                if( poolingType == MAX)
                     for( ; x0 < x1; x0++ )
                     {
-                        int xstart, xend;
-                        if (poolingType == ROI)
-                        {
-                            xstart = xstartROI + x0 * roiRatio;
-                            xend = xstartROI + std::ceil((x0 + 1) * roiRatio);
-                        }
-                        else
-                        {
-                            xstart = x0 * stride_w - pad_w;
-                            xend = xstart + kernel_w;
-                        }
+                        int xstart = x0 * stride_w - pad_w;
+                        int xend = min(xstart + kernel_w, inp_width);
                         xstart = max(xstart, 0);
-                        xend = min(xend, inp_width);
                         if (xstart >= xend || ystart >= yend)
                         {
                             dstData[x0] = 0;
@@ -493,7 +477,7 @@ public:
                             }
                         }
                     }
-                else
+                else if (poolingType == AVE)
                 {
                     for( ; x0 < x1; x0++ )
                     {
@@ -543,6 +527,37 @@ public:
                         }
                     }
                 }
+                else  // ROI
+                {
+                    const float *roisData = rois->ptr<float>(n);
+                    int xstartROI = scaleAndRoundRoi(roisData[1], spatialScale);
+                    int xendROI = scaleAndRoundRoi(roisData[3], spatialScale);
+                    int roiWidth = std::max(xendROI - xstartROI + 1, 1);
+                    float roiRatio = (float)roiWidth / width;
+                    for( ; x0 < x1; x0++ )
+                    {
+                        int xstart = xstartROI + x0 * roiRatio;
+                        int xend = xstartROI + std::ceil((x0 + 1) * roiRatio);
+                        xstart = max(xstart, 0);
+                        xend = min(xend, inp_width);
+                        if (xstart >= xend || ystart >= yend)
+                        {
+                            dstData[x0] = 0;
+                            if (compMaxIdx && dstMaskData)
+                                dstMaskData[x0] = -1;
+                            continue;
+                        }
+                        float max_val = -FLT_MAX;
+                        for (int y = ystart; y < yend; ++y)
+                            for (int x = xstart; x < xend; ++x)
+                            {
+                                const int index = y * inp_width + x;
+                                float val = srcData[index];
+                                max_val = std::max(max_val, val);
+                            }
+                        dstData[x0] = max_val;
+                    }
+                }
             }
         }
     };

modules/dnn/src/layers/prior_box_layer.cpp

@@ -183,6 +183,7 @@ public:
         _minSize = getParameter<float>(params, "min_size", 0, false, 0);
         _flip = getParameter<bool>(params, "flip", 0, false, true);
         _clip = getParameter<bool>(params, "clip", 0, false, true);
+        _bboxesNormalized = getParameter<bool>(params, "normalized_bbox", 0, false, true);
 
         _scales.clear();
         _aspectRatios.clear();
@@ -251,7 +252,7 @@ public:
                          std::vector<MatShape> &outputs,
                          std::vector<MatShape> &internals) const
     {
-        CV_Assert(inputs.size() == 2);
+        CV_Assert(!inputs.empty());
 
         int layerHeight = inputs[0][2];
         int layerWidth = inputs[0][3];
@@ -282,6 +283,8 @@ public:
         CV_TRACE_FUNCTION();
         CV_TRACE_ARG_VALUE(name, "name", name.c_str());
 
+        CV_Assert(inputs.size() == 2);
+
         size_t real_numPriors = _numPriors / pow(2, _offsetsX.size() - 1);
         if (_scales.empty())
             _scales.resize(real_numPriors, 1.0f);
@@ -323,7 +326,8 @@ public:
                 {
                     float center_x = (w + _offsetsX[i]) * stepX;
                     float center_y = (h + _offsetsY[i]) * stepY;
-                    outputPtr = addPrior(center_x, center_y, _boxWidth, _boxHeight, _imageWidth, _imageHeight, outputPtr);
+                    outputPtr = addPrior(center_x, center_y, _boxWidth, _boxHeight, _imageWidth,
+                                         _imageHeight, _bboxesNormalized, outputPtr);
                 }
                 if (_maxSize > 0)
                 {
@@ -333,7 +337,8 @@ public:
                     {
                         float center_x = (w + _offsetsX[i]) * stepX;
                         float center_y = (h + _offsetsY[i]) * stepY;
-                        outputPtr = addPrior(center_x, center_y, _boxWidth, _boxHeight, _imageWidth, _imageHeight, outputPtr);
+                        outputPtr = addPrior(center_x, center_y, _boxWidth, _boxHeight, _imageWidth,
+                                             _imageHeight, _bboxesNormalized, outputPtr);
                     }
                 }
 
@@ -349,7 +354,8 @@ public:
                     {
                         float center_x = (w + _offsetsX[i]) * stepX;
                         float center_y = (h + _offsetsY[i]) * stepY;
-                        outputPtr = addPrior(center_x, center_y, _boxWidth, _boxHeight, _imageWidth, _imageHeight, outputPtr);
+                        outputPtr = addPrior(center_x, center_y, _boxWidth, _boxHeight, _imageWidth,
+                                             _imageHeight, _bboxesNormalized, outputPtr);
                     }
                 }
 
@@ -363,7 +369,8 @@ public:
                     {
                         float center_x = (w + _offsetsX[j]) * stepX;
                         float center_y = (h + _offsetsY[j]) * stepY;
-                        outputPtr = addPrior(center_x, center_y, _boxWidth, _boxHeight, _imageWidth, _imageHeight, outputPtr);
+                        outputPtr = addPrior(center_x, center_y, _boxWidth, _boxHeight, _imageWidth,
+                                             _imageHeight, _bboxesNormalized, outputPtr);
                     }
                 }
             }
@@ -437,6 +444,7 @@ private:
     bool _flip;
     bool _clip;
     bool _explicitSizes;
+    bool _bboxesNormalized;
 
     size_t _numPriors;
 
@@ -444,12 +452,22 @@ private:
     static const std::string _layerName;
 
     static float* addPrior(float center_x, float center_y, float width, float height,
-                           float imgWidth, float imgHeight, float* dst)
+                           float imgWidth, float imgHeight, bool normalized, float* dst)
     {
-        dst[0] = (center_x - width * 0.5f) / imgWidth;    // xmin
-        dst[1] = (center_y - height * 0.5f) / imgHeight;  // ymin
-        dst[2] = (center_x + width * 0.5f) / imgWidth;    // xmax
-        dst[3] = (center_y + height * 0.5f) / imgHeight;  // ymax
+        if (normalized)
+        {
+            dst[0] = (center_x - width * 0.5f) / imgWidth;    // xmin
+            dst[1] = (center_y - height * 0.5f) / imgHeight;  // ymin
+            dst[2] = (center_x + width * 0.5f) / imgWidth;    // xmax
+            dst[3] = (center_y + height * 0.5f) / imgHeight;  // ymax
+        }
+        else
+        {
+            dst[0] = center_x - width * 0.5f;          // xmin
+            dst[1] = center_y - height * 0.5f;         // ymin
+            dst[2] = center_x + width * 0.5f - 1.0f;   // xmax
+            dst[3] = center_y + height * 0.5f - 1.0f;  // ymax
+        }
         return dst + 4;
     }
 };

modules/dnn/src/layers/proposal_layer.cpp

+// This file is part of OpenCV project.
+// It is subject to the license terms in the LICENSE file found in the top-level directory
+// of this distribution and at http://opencv.org/license.html.
+
+// Copyright (C) 2017, Intel Corporation, all rights reserved.
+// Third party copyrights are property of their respective owners.
+#include "../precomp.hpp"
+#include "layers_common.hpp"
+
+namespace cv { namespace dnn {
+
+class ProposalLayerImpl : public ProposalLayer
+{
+public:
+    ProposalLayerImpl(const LayerParams& params)
+    {
+        setParamsFrom(params);
+
+        uint32_t featStride = params.get<uint32_t>("feat_stride", 16);
+        uint32_t baseSize = params.get<uint32_t>("base_size", 16);
+        // uint32_t minSize = params.get<uint32_t>("min_size", 16);
+        uint32_t keepTopBeforeNMS = params.get<uint32_t>("pre_nms_topn", 6000);
+        keepTopAfterNMS = params.get<uint32_t>("post_nms_topn", 300);
+        float nmsThreshold = params.get<float>("nms_thresh", 0.7);
+        DictValue ratios = params.get("ratio");
+        DictValue scales = params.get("scale");
+
+        {
+            LayerParams lp;
+            lp.set("step", featStride);
+            lp.set("flip", false);
+            lp.set("clip", false);
+            lp.set("normalized_bbox", false);
+
+            // Unused values.
+            float variance[] = {0.1f, 0.1f, 0.2f, 0.2f};
+            lp.set("variance", DictValue::arrayReal<float*>(&variance[0], 4));
+
+            // Compute widths and heights explicitly.
+            std::vector<float> widths, heights;
+            widths.reserve(ratios.size() * scales.size());
+            heights.reserve(ratios.size() * scales.size());
+            for (int i = 0; i < ratios.size(); ++i)
+            {
+                float ratio = ratios.get<float>(i);
+                for (int j = 0; j < scales.size(); ++j)
+                {
+                    float scale = scales.get<float>(j);
+                    float width = std::floor(baseSize / sqrt(ratio) + 0.5f);
+                    float height = std::floor(width * ratio + 0.5f);
+                    widths.push_back(scale * width);
+                    heights.push_back(scale * height);
+                }
+            }
+            lp.set("width", DictValue::arrayReal<float*>(&widths[0], widths.size()));
+            lp.set("height", DictValue::arrayReal<float*>(&heights[0], heights.size()));
+
+            priorBoxLayer = PriorBoxLayer::create(lp);
+        }
+        {
+            int order[] = {0, 2, 3, 1};
+            LayerParams lp;
+            lp.set("order", DictValue::arrayInt<int*>(&order[0], 4));
+
+            deltasPermute = PermuteLayer::create(lp);
+            scoresPermute = PermuteLayer::create(lp);
+        }
+        {
+            LayerParams lp;
+            lp.set("code_type", "CENTER_SIZE");
+            lp.set("num_classes", 1);
+            lp.set("share_location", true);
+            lp.set("background_label_id", 1);  // We won't pass background scores so set it out of range [0, num_classes)
+            lp.set("variance_encoded_in_target", true);
+            lp.set("keep_top_k", keepTopAfterNMS);
+            lp.set("top_k", keepTopBeforeNMS);
+            lp.set("nms_threshold", nmsThreshold);
+            lp.set("normalized_bbox", false);
+            lp.set("clip", true);
+
+            detectionOutputLayer = DetectionOutputLayer::create(lp);
+        }
+    }
+
+    bool getMemoryShapes(const std::vector<MatShape> &inputs,
+                         const int requiredOutputs,
+                         std::vector<MatShape> &outputs,
+                         std::vector<MatShape> &internals) const
+    {
+        // We need to allocate the following blobs:
+        // - output priors from PriorBoxLayer
+        // - permuted priors
+        // - permuted scores
+        CV_Assert(inputs.size() == 3);
+
+        const MatShape& scores = inputs[0];
+        const MatShape& bboxDeltas = inputs[1];
+
+        std::vector<MatShape> layerInputs, layerOutputs, layerInternals;
+
+        // Prior boxes layer.
+        layerInputs.assign(1, scores);
+        priorBoxLayer->getMemoryShapes(layerInputs, 1, layerOutputs, layerInternals);
+        CV_Assert(layerOutputs.size() == 1);
+        CV_Assert(layerInternals.empty());
+        internals.push_back(layerOutputs[0]);
+
+        // Scores permute layer.
+        CV_Assert(scores.size() == 4);
+        MatShape objectScores = scores;
+        CV_Assert((scores[1] & 1) == 0);  // Number of channels is even.
+        objectScores[1] /= 2;
+        layerInputs.assign(1, objectScores);
+        scoresPermute->getMemoryShapes(layerInputs, 1, layerOutputs, layerInternals);
+        CV_Assert(layerOutputs.size() == 1);
+        CV_Assert(layerInternals.empty());
+        internals.push_back(layerOutputs[0]);
+
+        // BBox predictions permute layer.
+        layerInputs.assign(1, bboxDeltas);
+        deltasPermute->getMemoryShapes(layerInputs, 1, layerOutputs, layerInternals);
+        CV_Assert(layerOutputs.size() == 1);
+        CV_Assert(layerInternals.empty());
+        internals.push_back(layerOutputs[0]);
+
+        outputs.resize(1, shape(keepTopAfterNMS, 5));
+        return false;
+    }
+
+    void finalize(const std::vector<Mat*> &inputs, std::vector<Mat> &outputs)
+    {
+        std::vector<Mat*> layerInputs;
+        std::vector<Mat> layerOutputs;
+
+        // Scores permute layer.
+        Mat scores = getObjectScores(*inputs[0]);
+        layerInputs.assign(1, &scores);
+        layerOutputs.assign(1, Mat(shape(scores.size[0], scores.size[2],
+                                         scores.size[3], scores.size[1]), CV_32FC1));
+        scoresPermute->finalize(layerInputs, layerOutputs);
+
+        // BBox predictions permute layer.
+        Mat* bboxDeltas = inputs[1];
+        CV_Assert(bboxDeltas->dims == 4);
+        layerInputs.assign(1, bboxDeltas);
+        layerOutputs.assign(1, Mat(shape(bboxDeltas->size[0], bboxDeltas->size[2],
+                                         bboxDeltas->size[3], bboxDeltas->size[1]), CV_32FC1));
+        deltasPermute->finalize(layerInputs, layerOutputs);
+    }
+
+    void forward(InputArrayOfArrays inputs_arr, OutputArrayOfArrays outputs_arr, OutputArrayOfArrays internals_arr)
+    {
+        CV_TRACE_FUNCTION();
+        CV_TRACE_ARG_VALUE(name, "name", name.c_str());
+
+        Layer::forward_fallback(inputs_arr, outputs_arr, internals_arr);
+    }
+
+    void forward(std::vector<Mat*> &inputs, std::vector<Mat> &outputs, std::vector<Mat> &internals)
+    {
+        CV_TRACE_FUNCTION();
+        CV_TRACE_ARG_VALUE(name, "name", name.c_str());
+
+        CV_Assert(inputs.size() == 3);
+        CV_Assert(internals.size() == 3);
+        const Mat& scores = *inputs[0];
+        const Mat& bboxDeltas = *inputs[1];
+        const Mat& imInfo = *inputs[2];
+        Mat& priorBoxes = internals[0];
+        Mat& permuttedScores = internals[1];
+        Mat& permuttedDeltas = internals[2];
+
+        CV_Assert(imInfo.total() >= 2);
+        // We've chosen the smallest data type because we need just a shape from it.
+        fakeImageBlob.create(shape(1, 1, imInfo.at<float>(0), imInfo.at<float>(1)), CV_8UC1);
+
+        // Generate prior boxes.
+        std::vector<Mat> layerInputs(2), layerOutputs(1, priorBoxes);
+        layerInputs[0] = scores;
+        layerInputs[1] = fakeImageBlob;
+        priorBoxLayer->forward(layerInputs, layerOutputs, internals);
+
+        // Permute scores.
+        layerInputs.assign(1, getObjectScores(scores));
+        layerOutputs.assign(1, permuttedScores);
+        scoresPermute->forward(layerInputs, layerOutputs, internals);
+
+        // Permute deltas.
+        layerInputs.assign(1, bboxDeltas);
+        layerOutputs.assign(1, permuttedDeltas);
+        deltasPermute->forward(layerInputs, layerOutputs, internals);
+
+        // Sort predictions by scores and apply NMS. DetectionOutputLayer allocates
+        // output internally because of different number of objects after NMS.
+        layerInputs.resize(4);
+        layerInputs[0] = permuttedDeltas;
+        layerInputs[1] = permuttedScores;
+        layerInputs[2] = priorBoxes;
+        layerInputs[3] = fakeImageBlob;
+
+        layerOutputs[0] = Mat();
+        detectionOutputLayer->forward(layerInputs, layerOutputs, internals);
+
+        // DetectionOutputLayer produces 1x1xNx7 output where N might be less or
+        // equal to keepTopAfterNMS. We fill the rest by zeros.
+        const int numDets = layerOutputs[0].total() / 7;
+        CV_Assert(numDets <= keepTopAfterNMS);
+
+        Mat src = layerOutputs[0].reshape(1, numDets).colRange(3, 7);
+        Mat dst = outputs[0].rowRange(0, numDets);
+        src.copyTo(dst.colRange(1, 5));
+        dst.col(0).setTo(0);  // First column are batch ids. Keep it zeros too.
+
+        if (numDets < keepTopAfterNMS)
+            outputs[0].rowRange(numDets, keepTopAfterNMS).setTo(0);
+    }
+
+private:
+    // A first half of channels are background scores. We need only a second one.
+    static Mat getObjectScores(const Mat& m)
+    {
+        CV_Assert(m.dims == 4);
+        CV_Assert(m.size[0] == 1);
+        int channels = m.size[1];
+        CV_Assert((channels & 1) == 0);
+        return slice(m, Range::all(), Range(channels / 2, channels));
+    }
+
+    Ptr<PriorBoxLayer> priorBoxLayer;
+    Ptr<DetectionOutputLayer> detectionOutputLayer;
+
+    Ptr<PermuteLayer> deltasPermute;
+    Ptr<PermuteLayer> scoresPermute;
+    uint32_t keepTopAfterNMS;
+    Mat fakeImageBlob;
+};
+
+
+Ptr<ProposalLayer> ProposalLayer::create(const LayerParams& params)
+{
+    return Ptr<ProposalLayer>(new ProposalLayerImpl(params));
+}
+
+}  // namespace dnn
+}  // namespace cv

modules/dnn/test/test_layers.cpp

@@ -576,4 +576,27 @@ TEST(Layer_Test_ROIPooling, Accuracy)
     normAssert(out, ref);
 }
 
+TEST(Layer_Test_FasterRCNN_Proposal, Accuracy)
+{
+    Net net = readNetFromCaffe(_tf("net_faster_rcnn_proposal.prototxt"));
+
+    Mat scores = blobFromNPY(_tf("net_faster_rcnn_proposal.scores.npy"));
+    Mat deltas = blobFromNPY(_tf("net_faster_rcnn_proposal.deltas.npy"));
+    Mat imInfo = (Mat_<float>(1, 3) << 600, 800, 1.6f);
+    Mat ref = blobFromNPY(_tf("net_faster_rcnn_proposal.npy"));
+
+    net.setInput(scores, "rpn_cls_prob_reshape");
+    net.setInput(deltas, "rpn_bbox_pred");
+    net.setInput(imInfo, "im_info");
+
+    Mat out = net.forward();
+
+    const int numDets = ref.size[0];
+    EXPECT_LE(numDets, out.size[0]);
+    normAssert(out.rowRange(0, numDets), ref);
+
+    if (numDets < out.size[0])
+        EXPECT_EQ(countNonZero(out.rowRange(numDets, out.size[0])), 0);
+}
+
 }

samples/dnn/faster_rcnn.cpp

+// Faster-RCNN models use custom layer called 'Proposal' written in Python. To
+// map it into OpenCV's layer replace a layer node with [type: 'Python'] to the
+// following definition:
+// layer {
+//   name: 'proposal'
+//   type: 'Proposal'
+//   bottom: 'rpn_cls_prob_reshape'
+//   bottom: 'rpn_bbox_pred'
+//   bottom: 'im_info'
+//   top: 'rois'
+//   proposal_param {
+//     ratio: 0.5
+//     ratio: 1.0
+//     ratio: 2.0
+//     scale: 8
+//     scale: 16
+//     scale: 32
+//   }
+// }
+#include <iostream>
+
+#include <opencv2/dnn.hpp>
+#include <opencv2/dnn/all_layers.hpp>
+#include <opencv2/imgproc.hpp>
+#include <opencv2/highgui.hpp>
+
+using namespace cv;
+using namespace dnn;
+
+const char* about = "This sample is used to run Faster-RCNN object detection "
+                    "models from https://github.com/rbgirshick/py-faster-rcnn with OpenCV.";
+
+const char* keys =
+    "{ help  h |     | print help message  }"
+    "{ proto p |     | path to .prototxt   }"
+    "{ model m |     | path to .caffemodel }"
+    "{ image i |     | path to input image }"
+    "{ conf  c | 0.8 | minimal confidence  }";
+
+const char* classNames[] = {
+    "__background__",
+    "aeroplane", "bicycle", "bird", "boat",
+    "bottle", "bus", "car", "cat", "chair",
+    "cow", "diningtable", "dog", "horse",
+    "motorbike", "person", "pottedplant",
+    "sheep", "sofa", "train", "tvmonitor"
+};
+
+static const int kInpWidth = 800;
+static const int kInpHeight = 600;
+
+int main(int argc, char** argv)
+{
+    // Parse command line arguments.
+    CommandLineParser parser(argc, argv, keys);
+    if (argc == 1 || parser.has("help"))
+    {
+        std::cout << about << std::endl;
+        return 0;
+    }
+
+    String protoPath = parser.get<String>("proto");
+    String modelPath = parser.get<String>("model");
+    String imagePath = parser.get<String>("image");
+    float confThreshold = parser.get<float>("conf");
+    CV_Assert(!protoPath.empty(), !modelPath.empty(), !imagePath.empty());
+
+    // Load a model.
+    Net net = readNetFromCaffe(protoPath, modelPath);
+
+    // Create a preprocessing layer that does final bounding boxes applying predicted
+    // deltas to objects locations proposals and doing non-maximum suppression over it.
+    LayerParams lp;
+    lp.set("code_type", "CENTER_SIZE");               // An every bounding box is [xmin, ymin, xmax, ymax]
+    lp.set("num_classes", 21);
+    lp.set("share_location", (int)false);             // Separate predictions for different classes.
+    lp.set("background_label_id", 0);
+    lp.set("variance_encoded_in_target", (int)true);
+    lp.set("keep_top_k", 100);
+    lp.set("nms_threshold", 0.3);
+    lp.set("normalized_bbox", (int)false);
+    Ptr<Layer> detectionOutputLayer = DetectionOutputLayer::create(lp);
+
+    Mat img = imread(imagePath);
+    resize(img, img, Size(kInpWidth, kInpHeight));
+    Mat blob = blobFromImage(img, 1.0, Size(), Scalar(102.9801, 115.9465, 122.7717), false, false);
+    Mat imInfo = (Mat_<float>(1, 3) << img.rows, img.cols, 1.6f);
+
+    net.setInput(blob, "data");
+    net.setInput(imInfo, "im_info");
+
+    std::vector<Mat> outs;
+    std::vector<String> outNames(3);
+    outNames[0] = "proposal";
+    outNames[1] = "bbox_pred";
+    outNames[2] = "cls_prob";
+    net.forward(outs, outNames);
+
+    Mat proposals = outs[0].colRange(1, 5).clone();  // Only last 4 columns.
+    Mat& deltas = outs[1];
+    Mat& scores = outs[2];
+
+    // Reshape proposals from Nx4 to 1x1xN*4
+    std::vector<int> shape(3, 1);
+    shape[2] = (int)proposals.total();
+    proposals = proposals.reshape(1, shape);
+
+    // Run postprocessing layer.
+    std::vector<Mat> layerInputs(3), layerOutputs(1), layerInternals;
+    layerInputs[0] = deltas.reshape(1, 1);
+    layerInputs[1] = scores.reshape(1, 1);
+    layerInputs[2] = proposals;
+    detectionOutputLayer->forward(layerInputs, layerOutputs, layerInternals);
+
+    // Draw detections.
+    Mat detections = layerOutputs[0];
+    const float* data = (float*)detections.data;
+    for (size_t i = 0; i < detections.total(); i += 7)
+    {
+        // An every detection is a vector [id, classId, confidence, left, top, right, bottom]
+        float confidence = data[i + 2];
+        if (confidence > confThreshold)
+        {
+            int classId = (int)data[i + 1];
+            int left = max(0, min((int)data[i + 3], img.cols - 1));
+            int top = max(0, min((int)data[i + 4], img.rows - 1));
+            int right = max(0, min((int)data[i + 5], img.cols - 1));
+            int bottom = max(0, min((int)data[i + 6], img.rows - 1));
+
+            // Draw a bounding box.
+            rectangle(img, Point(left, top), Point(right, bottom), Scalar(0, 255, 0));
+
+            // Put a label with a class name and confidence.
+            String label = cv::format("%s, %.3f", classNames[classId], confidence);
+            int baseLine;
+            Size labelSize = cv::getTextSize(label, FONT_HERSHEY_SIMPLEX, 0.5, 1, &baseLine);
+
+            top = max(top, labelSize.height);
+            rectangle(img, Point(left, top - labelSize.height),
+                      Point(left + labelSize.width, top + baseLine),
+                      Scalar(255, 255, 255), FILLED);
+            putText(img, label, Point(left, top), FONT_HERSHEY_SIMPLEX, 0.5, Scalar(0, 0, 0));
+        }
+    }
+    imshow("frame", img);
+    waitKey();
+    return 0;
+}