Added one sample in tutorial_code to use Stereo Block matching

samples/cpp/tutorial_code/calib3d/stereoBM/SBM_Sample.cpp

+/**
+ * @file SBM_Sample
+ * @brief Get a disparity map of two images
+ * @author A. Huaman
+ */
+
+#include <stdio.h>
+#include <iostream>
+#include "opencv2/calib3d/calib3d.hpp"
+#include "opencv2/core/core.hpp"
+#include "opencv2/highgui/highgui.hpp"
+
+using namespace cv;
+
+char *windowDisparity = "Disparity";
+
+void readme();
+
+/**
+ * @function main
+ * @brief Main function
+ */
+int main( int argc, char** argv )
+{
+  if( argc != 3 )
+  { readme(); return -1; }
+
+  //-- 1. Read the images
+  Mat imgLeft = imread( argv[1], CV_LOAD_IMAGE_GRAYSCALE );
+  Mat imgRight = imread( argv[2], CV_LOAD_IMAGE_GRAYSCALE );
+  //-- And create the image in which we will save our disparities
+  Mat imgDisparity16S = Mat( imgLeft.rows, imgLeft.cols, CV_16S );
+  Mat imgDisparity8U = Mat( imgLeft.rows, imgLeft.cols, CV_8UC1 );
+  
+  if( !imgLeft.data || !imgRight.data )
+  { std::cout<< " --(!) Error reading images " << std::endl; return -1; }
+
+  //-- 2. Call the constructor for StereoBM
+  int ndisparities = 16*5;   /**< Range of disparity */
+  int SADWindowSize = 21; /**< Size of the block window. Must be odd */
+
+  StereoBM sbm( StereoBM::BASIC_PRESET,
+								ndisparities, 
+                SADWindowSize );
+
+  //-- 3. Calculate the disparity image
+  sbm( imgLeft, imgRight, imgDisparity16S, CV_16S );
+
+  //-- Check its extreme values
+  double minVal; double maxVal;
+
+  minMaxLoc( imgDisparity16S, &minVal, &maxVal );
+
+  printf("Min disp: %f Max value: %f \n", minVal, maxVal);
+
+  //-- 4. Display it as a CV_8UC1 image
+  imgDisparity16S.convertTo( imgDisparity8U, CV_8UC1, 255/(maxVal - minVal));
+
+  namedWindow( windowDisparity, CV_WINDOW_NORMAL );
+  imshow( windowDisparity, imgDisparity8U );
+
+  //-- 5. Save the image
+  imwrite("SBM_sample.png", imgDisparity16S);
+
+  waitKey(0);
+
+  return 0;
+}
+
+/**
+ * @function readme
+ */
+void readme()
+{ std::cout << " Usage: ./SBMSample <imgLeft> <imgRight>" << std::endl; }