adds MSERsToERStats function and its documentation; adds webcam_demo sample code…

adds MSERsToERStats function and its documentation; adds webcam_demo sample code and modifies cmakelists to link with features2d module

modules/text/CMakeLists.txt

@@ -18,7 +18,7 @@ include_directories(${Tesseract_INCLUDE_DIR})
 endif()
 
 set(the_description "Text Detection and Recognition")
-ocv_define_module(text opencv_ml opencv_highgui opencv_imgproc opencv_core)
+ocv_define_module(text opencv_ml opencv_highgui opencv_imgproc opencv_core opencv_features2d)
 
 if(${Tesseract_FOUND})
   target_link_libraries(opencv_text ${Tesseract_LIBS})

modules/text/doc/erfilter.rst

@@ -81,6 +81,20 @@ An ER is a 4-connected set of pixels with all its grey-level values smaller than
         ERStat* prev;
     };
 
+MSERsToERStats
+--------------
+Converts MSER contours (vector<Point>) to ERStat regions.
+
+.. ocv:function:: void MSERsToERStats(InputArray image, vector< vector<Point> > &contours, vector< vector<ERStat> > &regions)
+
+    :param image: Source image ``CV_8UC1`` from which the MSERs where extracted.
+    :param contours: Intput vector with all the contours (vector<Point>).
+    :param regions: Output where the ERStat regions are stored.
+
+It takes as input the contours provided by the OpenCV MSER feature detector and returns as output two vectors of ERStats. This is because MSER() output contains both MSER+ and MSER- regions in a single vector<Point>, the function separates them in two different vectors (this is as if the ERStats where extracted from two different channels).
+
+An example of MSERsToERStats in use can be found in the text detection webcam_demo: https://github.com/Itseez/opencv_contrib/blob/master/modules/text/samples/webcam_demo.cpp
+
 computeNMChannels
 -----------------
 Compute the different channels to be processed independently in the N&M algorithm [Neumann12].

modules/text/include/opencv2/text/erfilter.hpp

@@ -274,6 +274,15 @@ CV_EXPORTS void erGrouping(InputArray img, InputArrayOfArrays channels,
                                            const std::string& filename = std::string(),
                                            float minProbablity = 0.5);
 
+/*!
+ * MSERsToERStats function converts MSER contours (vector<Point>) to ERStat regions.
+ * It takes as input the contours provided by the OpenCV MSER feature detector and returns as output two vectors
+ * of ERStats. MSER output contains both MSER+ and MSER- regions in a single vector<Point>, the function separates
+ * them in two different vectors (this is the ERStats where extracted from two different channels).
+ * */
+CV_EXPORTS void MSERsToERStats(InputArray image, std::vector<std::vector<Point> > &contours,
+                               std::vector<std::vector<ERStat> > &regions);
+
 }
 }
 #endif // _OPENCV_TEXT_ERFILTER_HPP_

modules/text/src/erfilter.cpp

@@ -4069,5 +4069,78 @@ void erGrouping(InputArray image, InputArrayOfArrays channels, vector<vector<ERS
 
 }
 
+/*!
+ * MSERsToERStats function converts MSER contours (vector<Point>) to ERStat regions.
+ * It takes as input the contours provided by the OpenCV MSER feature detector and returns as output two vectors
+ * of ERStats. MSER output contains both MSER+ and MSER- regions in a single vector<Point>, the function separates
+ * them in two different vectors (this is the ERStats where extracted from two different channels).
+ * */
+void MSERsToERStats(InputArray image, vector<vector<Point> > &contours, vector<vector<ERStat> > &mser_regions)
+{
+
+  CV_Assert(!contours.empty());
+  Mat grey = image.getMat();
+  // assert correct image type
+  CV_Assert( grey.type() == CV_8UC1 );
+  if (!mser_regions.empty())
+    mser_regions.clear();
+
+  //MSER output contains both MSER+ and MSER- regions in a single vector but we want them separated
+  mser_regions.resize(2);
+
+  //Append "fake" root region to simulate a tree structure (needed for grouping)
+  ERStat fake_root;
+  mser_regions[0].push_back(fake_root);
+  mser_regions[1].push_back(fake_root);
+
+  Mat mask = Mat::zeros(grey.rows, grey.cols, CV_8UC1);
+  Mat mtmp = Mat::zeros(grey.rows, grey.cols, CV_8UC1);
+  for (int i=0; i<(int)contours.size(); i++)
+  {
+
+    ERStat cser;
+    cser.area = contours[i].size();
+    cser.rect = boundingRect(contours[i]);
+
+    float avg_intensity = 0;
+    const vector<Point>& r = contours[i];
+    for ( int j = 0; j < (int)r.size(); j++ )
+    {
+      Point pt = r[j];
+      mask.at<unsigned char>(pt) = 255;
+      avg_intensity += (float)grey.at<unsigned char>(pt)/(int)r.size();
+    }
+
+    double min, max;
+    Point min_loc, max_loc;
+    minMaxLoc(grey(cser.rect), &min, &max, &min_loc, &max_loc, mask(cser.rect));
+
+    Mat element = getStructuringElement( MORPH_RECT, Size(5,5), Point(2,2) );
+    dilate( mask(cser.rect), mtmp(cser.rect), element );
+    absdiff( mtmp(cser.rect), mask(cser.rect), mtmp(cser.rect) );
+
+    Scalar mean,std;
+    meanStdDev(grey(cser.rect), mean, std, mtmp(cser.rect) );
+
+    if (avg_intensity < mean[0])
+    {
+      cser.level  = (int)max;
+      cser.pixel  = (max_loc.y+cser.rect.y)*grey.cols+max_loc.x+cser.rect.x;
+      cser.parent = &(mser_regions[0][0]);
+      mser_regions[0].push_back(cser);
+    }
+    else
+    {
+      cser.level  = 255-(int)min;
+      cser.pixel  = (min_loc.y+cser.rect.y)*grey.cols+min_loc.x+cser.rect.x;
+      cser.parent = &(mser_regions[1][0]);
+      mser_regions[1].push_back(cser);
+    }
+
+    mask(cser.rect) = 0;
+    mtmp(cser.rect) = 0;
+  }
+}
+
 }
 }