G-API fluid kernel sample

fluid_kernel_sample.cpp

#include <opencv2/core.hpp>
#include <opencv2/imgcodecs.hpp>
#include <opencv2/highgui.hpp>
#include <opencv2/gapi.hpp>
#include <opencv2/gapi/core.hpp>
#include <opencv2/gapi/imgproc.hpp>
#include <opencv2/gapi/fluid/gfluidkernel.hpp>

G_TYPED_KERNEL(TBitwiseNot, <cv::GMat(cv::GMat)>, "sample.fluid.bitwise_not")
{
    static cv::GMatDesc outMeta(cv::GMatDesc in)
    {
        return in;
    }
};

GAPI_FLUID_KERNEL(FBitwiseNot, TBitwiseNot, false)
{
    static const int Window = 1;
    static void run(const cv::gapi::fluid::View &src, cv::gapi::fluid::Buffer &dst)
    {
        const uint8_t* in = src.InLine<uint8_t>(0);
        uint8_t* out = dst.OutLine<uint8_t>();
        for (int i = 0, w = src.length(); i < w; i++)
        {
            out[i] = UINT8_MAX - in[i];
        }
    }
};

int main(int argc, const char* argv[])
{
    cv::Mat src = cv::imread("graf1.png", cv::IMREAD_COLOR);
    if (src.empty())
    {
        std::cerr << "could not load image." << std::endl;
        return -1;
    }

    cv::GMat in;
    cv::GMat gray = cv::gapi::BGR2Gray(in);
    cv::GMat out = TBitwiseNot::on(gray);
    cv::GComputation ac(in, out);

    cv::gapi::GKernelPackage fluid_kernel = cv::gapi::kernels<FBitwiseNot>();
    cv::Mat dst;
    ac.apply(src, dst, cv::compile_args(fluid_kernel));
    cv::imshow("dst", dst);
    cv::waitKey(0);

    return 0;
}