Partial DIS implementation and OF benchmark

Basic interfaces and a partial implementation of the Dense Inverse
Search (DIS) optical flow algorithm without variational refinement. Also
added a python benchmarking script that can evaluate different optical
flow algorithms on the MPI Sintel and Middlebury datasets and build
overall comparative charts.

modules/optflow/doc/optflow.bib

@@ -37,3 +37,10 @@
   year={2013},
   organization={IEEE}
 }
+
+@article{Kroeger2016,
+  title={Fast Optical Flow using Dense Inverse Search},
+  author={Kroeger, Till and Timofte, Radu and Dai, Dengxin and Van Gool, Luc},
+  journal={arXiv preprint arXiv:1603.03590},
+  year={2016}
+}

modules/optflow/include/opencv2/optflow.hpp

@@ -191,6 +191,44 @@ CV_EXPORTS_W Ptr<DenseOpticalFlow> createOptFlow_Farneback();
 //! Additional interface to the SparseToDenseFlow algorithm - calcOpticalFlowSparseToDense()
 CV_EXPORTS_W Ptr<DenseOpticalFlow> createOptFlow_SparseToDense();
 
+/** @brief DIS optical flow algorithm.
+
+This class implements the Dense Inverse Search (DIS) optical flow algorithm. More
+details about the algorithm can be found at @cite Kroeger2016 .
+*/
+class CV_EXPORTS_W DISOpticalFlow : public DenseOpticalFlow
+{
+public:
+    /** @brief Finest level of the gaussian pyramid on which the flow is computed (zero level
+        corresponds to the original image resolution).The final flow is obtained by bilinear upscaling.
+        @see setFinestScale */
+    virtual int getFinestScale() const = 0;
+    /** @copybrief getFinestScale @see getFinestScale */
+    virtual void setFinestScale(int val) = 0;
+
+    /** @brief Size of an image patch for matching (in pixels)
+        @see setPatchSize */
+    virtual int getPatchSize() const = 0;
+    /** @copybrief getPatchSize @see getPatchSize */
+    virtual void setPatchSize(int val) = 0;
+
+    /** @brief Stride between neighbor patches. Must be less than patch size.
+        @see setPatchStride */
+    virtual int getPatchStride() const = 0;
+    /** @copybrief getPatchStride @see getPatchStride */
+    virtual void setPatchStride(int val) = 0;
+
+    /** @brief number of gradient descent iterations in the patch inverse search stage
+        @see setGradientDescentIterations */
+    virtual int getGradientDescentIterations() const = 0;
+    /** @copybrief getGradientDescentIterations @see getGradientDescentIterations */
+    virtual void setGradientDescentIterations(int val) = 0;
+};
+
+/** @brief Creates an instance of DISOpticalFlow
+*/
+CV_EXPORTS_W Ptr<DISOpticalFlow> createOptFlow_DIS();
+
 //! @}
 
 } //optflow

modules/optflow/samples/optical_flow_evaluation.cpp

@@ -11,7 +11,7 @@ using namespace optflow;
 const String keys = "{help h usage ? |      | print this message   }"
         "{@image1        |      | image1               }"
         "{@image2        |      | image2               }"
-        "{@algorithm     |      | [farneback, simpleflow, tvl1, deepflow or sparsetodenseflow] }"
+        "{@algorithm     |      | [farneback, simpleflow, tvl1, deepflow, sparsetodenseflow or DISflow] }"
         "{@groundtruth   |      | path to the .flo file  (optional), Middlebury format }"
         "{m measure      |endpoint| error measure - [endpoint or angular] }"
         "{r region       |all   | region to compute stats about [all, discontinuities, untextured] }"
@@ -229,7 +229,7 @@ int main( int argc, char** argv )
     if ( i2.depth() != CV_8U )
         i2.convertTo(i2, CV_8U);
 
-    if ( (method == "farneback" || method == "tvl1" || method == "deepflow") && i1.channels() == 3 )
+    if ( (method == "farneback" || method == "tvl1" || method == "deepflow" || method == "DISflow") && i1.channels() == 3 )
     {   // 1-channel images are expected
         cvtColor(i1, i1, COLOR_BGR2GRAY);
         cvtColor(i2, i2, COLOR_BGR2GRAY);
@@ -252,6 +252,8 @@ int main( int argc, char** argv )
         algorithm = createOptFlow_DeepFlow();
     else if ( method == "sparsetodenseflow" )
         algorithm = createOptFlow_SparseToDense();
+    else if ( method == "DISflow" )
+        algorithm = createOptFlow_DIS();
     else
     {
         printf("Wrong method!\n");