add part of opencv

Lib/opencv/sources/modules/gapi/samples/slides_sobel_gapi.cpp

@@ -0,0 +1,28 @@
+#include <opencv2/videoio.hpp>
+#include <opencv2/highgui.hpp>
+#include <opencv2/gapi.hpp>
+#include <opencv2/gapi/core.hpp>
+#include <opencv2/gapi/imgproc.hpp>
+
+int main(int argc, char *argv[])
+{
+    (void) argc;
+    (void) argv;
+
+    using namespace cv;
+    Mat in_mat = imread("lena.png");
+    Mat out_mat;
+
+    GMat in;
+    GMat gx  = gapi::Sobel(in, CV_32F, 1, 0);
+    GMat gy  = gapi::Sobel(in, CV_32F, 0, 1);
+    GMat mag = gapi::sqrt(  gapi::mul(gx, gx)
+                          + gapi::mul(gy, gy));
+    GMat out = gapi::convertTo(mag, CV_8U);
+
+    GComputation sobel(GIn(in), GOut(out));
+    sobel.apply(in_mat, out_mat);
+
+    imwrite("lena-out.png", out_mat);
+    return 0;
+}