Merge pull request #16066 from dmatveev:dm/gapi_slides

* G-API: Added G-API Overview slides & its source code

- Sample code snippets are moved to separate files;
- Introduced a separate benchmark to measure Fluid/OpenCV
  performance;
- Added notes on API changes (it is still a 4.0, not a 4.2 talk!)
- Added a "Metropolis" beamer download-n-build script.

* G-API: Addressed review issues on G-API overview slides

modules/gapi/doc/slides/.gitignore

+*.bbl
+*.blg
+*.sty
+*.tex
+*-converted-to.pdf
+mtheme.sty/

modules/gapi/doc/slides/README.md

+# G-API Overview
+
+This is the latest overview slide deck on G-API.
+
+## Prerequisites
+
+- [Emacs] v24 or higher;
+- [Org]-mode 8.2.10;
+- `pdflatex`;
+- `texlive-latex-recommended` ([Beamer] package);
+- `texlive-font-utils` (`epstopdf`);
+- `wget` (for `get_sty.sh`).
+
+## Building
+
+1. Download and build the [Metropolis] theme with the script:
+
+```
+$ ./get_sty.sh
+```
+
+2. Now open `gapi_overview.org` with Emacs and press `C-c C-e l P`.
+
+[Emacs]:      https://www.gnu.org/software/emacs/
+[Org]:        https://orgmode.org/
+[Beamer]:     https://ctan.org/pkg/beamer
+[Metropolis]: https://github.com/matze/mtheme

modules/gapi/doc/slides/get_sty.sh

+#!/usr/bin/env bash
+
+set -e
+
+MTHEME_VER=2fa6084b9d34fec9d2d5470eb9a17d0bf712b6c8
+MTHEME_DIR=mtheme.sty
+
+function make_sty {
+    if [ -d "$MTHEME_DIR" ]; then rm -rf "$MTHEME_DIR"; fi
+    mkdir "$MTHEME_DIR"
+
+    # Download template from Github
+    tmp_dir=$(mktemp -d)
+    wget -P "$tmp_dir" -c https://github.com/matze/mtheme/archive/${MTHEME_VER}.tar.gz
+    pushd "$tmp_dir"
+    tar -xzvf "$MTHEME_VER.tar.gz"
+    popd
+    make -C "$tmp_dir"/mtheme-"$MTHEME_VER"
+    cp   -v "$tmp_dir"/mtheme-"$MTHEME_VER"/*.sty "$MTHEME_DIR"
+    rm -r "$tmp_dir"
+    # Put our own .gitignore to ignore this directory completely
+    echo "*" > "$MTHEME_DIR/.gitignore"
+}
+
+make_sty

modules/gapi/doc/slides/ocv_logo.eps

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modules/gapi/perf/cpu/gapi_core_perf_tests_cpu.cpp

@@ -288,4 +288,4 @@ INSTANTIATE_TEST_CASE_P(ResizeFxFyPerfTestCPU, ResizeFxFyPerfTest,
         Values(0.5, 0.1),
         Values(0.5, 0.1),
         Values(cv::compile_args(CORE_CPU))));
-}
+} // opencv_test

modules/gapi/perf/perf_bench.cpp

+#include "perf_precomp.hpp"
+#include "../test/common/gapi_tests_common.hpp"
+
+namespace opencv_test
+{
+
+struct SobelEdgeDetector:  public TestPerfParams<cv::Size> {};
+PERF_TEST_P_(SobelEdgeDetector, Fluid)
+{
+    Size sz = GetParam();
+    initMatsRandU(CV_8UC3, sz, CV_8UC3, false);
+
+    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(in, out);
+    auto pkg = gapi::combine(gapi::core::fluid::kernels(),
+                             gapi::imgproc::fluid::kernels());
+    auto cc = sobel.compile(cv::descr_of(in_mat1),
+                            cv::compile_args(cv::gapi::use_only{pkg}));
+    cc(in_mat1, out_mat_gapi);
+
+    TEST_CYCLE()
+    {
+        cc(in_mat1, out_mat_gapi);
+    }
+    SANITY_CHECK_NOTHING();
+}
+PERF_TEST_P_(SobelEdgeDetector, OpenCV)
+{
+    Size sz = GetParam();
+    initMatsRandU(CV_8UC3, sz, CV_8UC3, false);
+
+    Mat gx, gy;
+    Mat mag;
+    auto cc = [&](const cv::Mat &in_mat, cv::Mat &out_mat) {
+        using namespace cv;
+
+        Sobel(in_mat, gx, CV_32F, 1, 0);
+        Sobel(in_mat, gy, CV_32F, 0, 1);
+        sqrt(gx.mul(gx) + gy.mul(gy), mag);
+        mag.convertTo(out_mat, CV_8U);
+    };
+    cc(in_mat1, out_mat_gapi);
+
+    TEST_CYCLE()
+    {
+        cc(in_mat1, out_mat_gapi);
+    }
+    SANITY_CHECK_NOTHING();
+}
+PERF_TEST_P_(SobelEdgeDetector, OpenCV_Smarter)
+{
+    Size sz = GetParam();
+    initMatsRandU(CV_8UC3, sz, CV_8UC3, false);
+
+    Mat gx, gy;
+    Mat ggx, ggy;
+    Mat sum;
+    Mat mag;
+
+    auto cc = [&](const cv::Mat &in_mat, cv::Mat &out_mat) {
+        cv::Sobel(in_mat, gx, CV_32F, 1, 0);
+        cv::Sobel(in_mat, gy, CV_32F, 0, 1);
+        cv::multiply(gx, gx, ggx);
+        cv::multiply(gy, gy, ggy);
+        cv::add(ggx, ggy, sum);
+        cv::sqrt(sum, mag);
+        mag.convertTo(out_mat, CV_8U);
+    };
+    cc(in_mat1, out_mat_gapi);
+
+    TEST_CYCLE()
+    {
+        cc(in_mat1, out_mat_gapi);
+    }
+    SANITY_CHECK_NOTHING();
+}
+INSTANTIATE_TEST_CASE_P(Benchmark, SobelEdgeDetector,
+                        Values(cv::Size(320, 240),
+                               cv::Size(640, 480),
+                               cv::Size(1280, 720),
+                               cv::Size(1920, 1080),
+                               cv::Size(3840, 2170)));
+
+} // opencv_test

modules/gapi/samples/slides_sobel_cv.cpp

+#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 gx, gy;
+
+    Sobel(in_mat, gx, CV_32F, 1, 0);
+    Sobel(in_mat, gy, CV_32F, 0, 1);
+
+    Mat mag;
+    sqrt(gx.mul(gx) + gy.mul(gy), mag);
+
+    Mat out_mat;
+    mag.convertTo(out_mat, CV_8U);
+
+    imwrite("lena-out.png", out_mat);
+    return 0;
+}

modules/gapi/samples/slides_sobel_gapi.cpp

+#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;
+}