Merge pull request #15942 from OrestChura:fb_tutorial

G-API: Tutorial: Face beautification algorithm implementation

* Introduce a tutorial on face beautification algorithm

- small typo issue in render_ocv.cpp

* Addressing comments rgarnov smirnov-alexey

doc/tutorials/gapi/table_of_content_gapi.markdown

@@ -29,3 +29,14 @@ how G-API module can be used for that.
     is ported on G-API, covering the basic intuition behind this
     transition process, and examining benefits which a graph model
     brings there.
+
+- @subpage tutorial_gapi_face_beautification
+
+    *Languages:* C++
+
+    *Compatibility:* \> OpenCV 4.2
+
+    *Author:* Orest Chura
+
+    In this tutorial we build a complex hybrid Computer Vision/Deep
+    Learning video processing pipeline with G-API.

modules/gapi/src/api/render_ocv.cpp

@@ -197,7 +197,7 @@ void drawPrimitivesOCV(cv::Mat& in,
                 const auto& ftp  = cv::util::get<FText>(p);
                 const auto color = converter.cvtColor(ftp.color);
 
-                GAPI_Assert(ftpr && "I must pass cv::gapi::wip::draw::freetype_font"
+                GAPI_Assert(ftpr && "You must pass cv::gapi::wip::draw::freetype_font"
                                     " to the graph compile arguments");
                 int baseline = 0;
                 auto size    = ftpr->getTextSize(ftp.text, ftp.fh, &baseline);