// This file is part of OpenCV project.
// It is subject to the license terms in the LICENSE file found in the top-level directory
// of this distribution and at http://opencv.org/license.html.
//
// Copyright (C) 2018 Intel Corporation

#if !defined(GAPI_STANDALONE)

#include "precomp.hpp"

#include <opencv2/gapi/own/assert.hpp>
#include <opencv2/core/traits.hpp>
#include <opencv2/imgproc/types_c.h>

#include <opencv2/gapi/core.hpp>
#include <opencv2/gapi/imgproc.hpp>

#include <opencv2/gapi/fluid/gfluidbuffer.hpp>
#include <opencv2/gapi/fluid/gfluidkernel.hpp>
#include <opencv2/gapi/fluid/imgproc.hpp>

#include "gfluidbuffer_priv.hpp"
#include "gfluidbackend.hpp"
#include "gfluidutils.hpp"

#include "gfluidimgproc_func.hpp"

#if CV_SSE4_1
#include "gfluidcore_simd_sse41.hpp"
#endif

#include <opencv2/imgproc/hal/hal.hpp>
#include <opencv2/core/hal/intrin.hpp>

#include <cmath>
#include <algorithm>

namespace cv {
namespace gapi {
namespace fluid {

//----------------------------------
//
// Fluid kernels: RGB2Gray, BGR2Gray
//
//----------------------------------

// Y' = 0.299*R' + 0.587*G' + 0.114*B'
// U' = (B' - Y')*0.492
// V' = (R' - Y')*0.877
static const float coef_rgb2yuv_bt601[5] = {0.299f, 0.587f, 0.114f, 0.492f, 0.877f};

// R' = Y' + 1.140*V'
// G' = Y' - 0.394*U' - 0.581*V'
// B' = Y' + 2.032*U'
static const float coef_yuv2rgb_bt601[4] = {1.140f, -0.394f, -0.581f, 2.032f};

static void run_rgb2gray(Buffer &dst, const View &src, float coef_r, float coef_g, float coef_b)
{
    GAPI_Assert(src.meta().depth == CV_8U);
    GAPI_Assert(dst.meta().depth == CV_8U);
    GAPI_Assert(src.meta().chan == 3);
    GAPI_Assert(dst.meta().chan == 1);
    GAPI_Assert(src.length() == dst.length());

    GAPI_Assert(coef_r < 1 && coef_g < 1 && coef_b < 1);
    GAPI_Assert(std::abs(coef_r + coef_g + coef_b - 1) < 0.001);

    const auto *in  = src.InLine<uchar>(0);
          auto *out = dst.OutLine<uchar>();

    int width = dst.length();

    run_rgb2gray_impl(out, in, width, coef_r, coef_g, coef_b);
}

GAPI_FLUID_KERNEL(GFluidRGB2GrayCustom, cv::gapi::imgproc::GRGB2GrayCustom, false)
{
    static const int Window = 1;

    static void run(const View &src, float coef_r, float coef_g, float coef_b, Buffer &dst)
    {
        run_rgb2gray(dst, src, coef_r, coef_g, coef_b);
    }
};

GAPI_FLUID_KERNEL(GFluidRGB2Gray, cv::gapi::imgproc::GRGB2Gray, false)
{
    static const int Window = 1;

    static void run(const View &src, Buffer &dst)
    {
        float coef_r = coef_rgb2yuv_bt601[0];
        float coef_g = coef_rgb2yuv_bt601[1];
        float coef_b = coef_rgb2yuv_bt601[2];
        run_rgb2gray(dst, src, coef_r, coef_g, coef_b);
    }
};

GAPI_FLUID_KERNEL(GFluidBGR2Gray, cv::gapi::imgproc::GBGR2Gray, false)
{
    static const int Window = 1;

    static void run(const View &src, Buffer &dst)
    {
        float coef_r = coef_rgb2yuv_bt601[0];
        float coef_g = coef_rgb2yuv_bt601[1];
        float coef_b = coef_rgb2yuv_bt601[2];
        run_rgb2gray(dst, src, coef_b, coef_g, coef_r);
    }
};

//--------------------------------------
//
// Fluid kernels: RGB-to-YUV, YUV-to-RGB
//
//--------------------------------------

static void run_rgb2yuv(Buffer &dst, const View &src, const float coef[5])
{
    GAPI_Assert(src.meta().depth == CV_8U);
    GAPI_Assert(dst.meta().depth == CV_8U);
    GAPI_Assert(src.meta().chan == 3);
    GAPI_Assert(dst.meta().chan == 3);
    GAPI_Assert(src.length() == dst.length());

    const auto *in  = src.InLine<uchar>(0);
          auto *out = dst.OutLine<uchar>();

    int width = dst.length();

    run_rgb2yuv_impl(out, in, width, coef);
}

static void run_yuv2rgb(Buffer &dst, const View &src, const float coef[4])
{
    GAPI_Assert(src.meta().depth == CV_8U);
    GAPI_Assert(dst.meta().depth == CV_8U);
    GAPI_Assert(src.meta().chan == 3);
    GAPI_Assert(dst.meta().chan == 3);
    GAPI_Assert(src.length() == dst.length());

    const auto *in  = src.InLine<uchar>(0);
          auto *out = dst.OutLine<uchar>();

    int width = dst.length();

    run_yuv2rgb_impl(out, in, width, coef);
}

GAPI_FLUID_KERNEL(GFluidRGB2YUV, cv::gapi::imgproc::GRGB2YUV, false)
{
    static const int Window = 1;

    static void run(const View &src, Buffer &dst)
    {
        run_rgb2yuv(dst, src, coef_rgb2yuv_bt601);
    }
};

GAPI_FLUID_KERNEL(GFluidYUV2RGB, cv::gapi::imgproc::GYUV2RGB, false)
{
    static const int Window = 1;

    static void run(const View &src, Buffer &dst)
    {
        run_yuv2rgb(dst, src, coef_yuv2rgb_bt601);
    }
};

//--------------------------------------
//
// Fluid kernels: RGB-to-Lab, BGR-to-LUV
//
//--------------------------------------

enum LabLUV { LL_Lab, LL_LUV };

#define LabLuv_reference 0  // 1=use reference code of RGB/BGR to LUV/Lab, 0=don't

#if LabLuv_reference

// gamma-correction (inverse) for sRGB, 1/gamma=2.4 for inverse, like for Mac OS (?)
static inline float f_gamma(float x)
{
    return x <= 0.04045f ? x*(1.f/12.92f) : std::pow((x + 0.055f)*(1/1.055f), 2.4f);
}

// saturate into interval [0, 1]
static inline float clip01(float value)
{
    return value < 0? 0:
           value > 1? 1:
           value;
}

static inline void f_rgb2xyz(float  R, float  G, float  B,
                             float& X, float& Y, float& Z)
{
    X = clip01(0.412453f*R + 0.357580f*G + 0.180423f*B);
    Y = clip01(0.212671f*R + 0.715160f*G + 0.072169f*B);
    Z = clip01(0.019334f*R + 0.119193f*G + 0.950227f*B);
}

static inline void f_xyz2lab(float  X, float  Y, float  Z,
                             float& L, float& a, float& b)
{
    // CIE XYZ values of reference white point for D65 illuminant
    static const float Xn = 0.950456f, Yn = 1.f, Zn = 1.088754f;

    // Other coefficients below:
    // 7.787f    = (29/3)^3/(29*4)
    // 0.008856f = (6/29)^3
    // 903.3     = (29/3)^3

    float x = X/Xn, y = Y/Yn, z = Z/Zn;

    auto f = [](float t){ return t>0.008856f? std::cbrt(t): (7.787f*t + 16.f/116.f); };

    float fx = f(x), fy = f(y), fz = f(z);

    L = y > 0.008856f ? (116.f*std::cbrt(y) - 16.f) : (903.3f * y);
    a = 500.f * (fx - fy);
    b = 200.f * (fy - fz);
}

static inline void f_xyz2luv(float  X, float  Y, float  Z,
                             float& L, float& u, float& v)
{
    static const float un = 0.19793943f, vn = 0.46831096f;

    float u1 = 4*X / (X + 15*Y + 3*Z);
    float v1 = 9*Y / (X + 15*Y + 3*Z);

    L = Y > 0.008856f ? (116.f*std::cbrt(Y) - 16.f) : (903.3f * Y);
    u = 13*L * (u1 - un);
    v = 13*L * (v1 - vn);
}

template<LabLUV labluv, int blue=0>
static void run_rgb2labluv_reference(uchar out[], const uchar in[], int width)
{
    for (int w=0; w < width; w++)
    {
        float R, G, B;
        B = in[3*w +    blue ] / 255.f;
        G = in[3*w +    1    ] / 255.f;
        R = in[3*w + (2^blue)] / 255.f;

        B = f_gamma( B );
        G = f_gamma( G );
        R = f_gamma( R );

        float X, Y, Z;
        f_rgb2xyz(R, G, B, X, Y, Z);

        // compile-time `if`
        if (LL_Lab == labluv)
        {
            float L, a, b;
            f_xyz2lab(X, Y, Z, L, a, b);

            out[3*w    ] = saturate<uchar>(L * 255.f/100, roundf);
            out[3*w + 1] = saturate<uchar>(a + 128, roundf);
            out[3*w + 2] = saturate<uchar>(b + 128, roundf);
        }
        else if (LL_LUV == labluv)
        {
            float L, u, v;
            f_xyz2luv(X, Y, Z, L, u, v);

            out[3*w    ] = saturate<uchar>( L        * 255.f/100, roundf);
            out[3*w + 1] = saturate<uchar>((u + 134) * 255.f/354, roundf);
            out[3*w + 2] = saturate<uchar>((v + 140) * 255.f/262, roundf);
        }
        else
            CV_Error(cv::Error::StsBadArg, "unsupported color conversion");;
    }
}

#endif  // LabLuv_reference

// compile-time parameters: output format (Lab/LUV),
// and position of blue channel in BGR/RGB (0 or 2)
template<LabLUV labluv, int blue=0>
static void run_rgb2labluv(Buffer &dst, const View &src)
{
    GAPI_Assert(src.meta().depth == CV_8U);
    GAPI_Assert(dst.meta().depth == CV_8U);
    GAPI_Assert(src.meta().chan == 3);
    GAPI_Assert(dst.meta().chan == 3);
    GAPI_Assert(src.length() == dst.length());

    const auto *in  = src.InLine<uchar>(0);
          auto *out = dst.OutLine<uchar>();

    int width = dst.length();

#if LabLuv_reference
    run_rgb2labluv_reference<labluv, blue>(out, in, width);
#else
    uchar *dst_data = out;
    const uchar *src_data = in;
    size_t src_step = width;
    size_t dst_step = width;
    int height = 1;
    int depth = CV_8U;
    int scn = 3;
    bool swapBlue = (blue == 2);
    bool isLab = (LL_Lab == labluv);
    bool srgb = true;
    cv::hal::cvtBGRtoLab(src_data, src_step, dst_data, dst_step,
               width, height, depth, scn, swapBlue, isLab, srgb);
#endif
}

GAPI_FLUID_KERNEL(GFluidRGB2Lab, cv::gapi::imgproc::GRGB2Lab, false)
{
    static const int Window = 1;

    static void run(const View &src, Buffer &dst)
    {
        static const int blue = 2; // RGB: 0=red, 1=green, 2=blue
        run_rgb2labluv<LL_Lab, blue>(dst, src);
    }
};

GAPI_FLUID_KERNEL(GFluidBGR2LUV, cv::gapi::imgproc::GBGR2LUV, false)
{
    static const int Window = 1;

    static void run(const View &src, Buffer &dst)
    {
        static const int blue = 0; // BGR: 0=blue, 1=green, 2=red
        run_rgb2labluv<LL_LUV, blue>(dst, src);
    }
};

//-------------------------------
//
// Fluid kernels: blur, boxFilter
//
//-------------------------------

static const int maxKernelSize = 9;

template<typename DST, typename SRC>
static void run_boxfilter(Buffer &dst, const View &src, const cv::Size &kernelSize,
                          const cv::Point& /* anchor */, bool normalize, float *buf[])
{
    GAPI_Assert(kernelSize.width <= maxKernelSize);
    GAPI_Assert(kernelSize.width == kernelSize.height);

    int kernel = kernelSize.width;
    int border = (kernel - 1) / 2;

    const SRC *in[ maxKernelSize ];
          DST *out;

    for (int i=0; i < kernel; i++)
    {
        in[i] = src.InLine<SRC>(i - border);
    }

    out = dst.OutLine<DST>();

    int width = dst.length();
    int chan  = dst.meta().chan;

    if (kernelSize.width == 3 && kernelSize.height == 3)
    {
        int y  = dst.y();
        int y0 = dst.priv().writeStart();

        float  kx[3] = {1, 1, 1};
        float *ky = kx;

        float scale=1, delta=0;
        if (normalize)
            scale = 1/9.f;

        run_sepfilter3x3_impl(out, in, width, chan, kx, ky, border, scale, delta, buf, y, y0);
    } else
    {
        GAPI_DbgAssert(chan <= 4);

        for (int w=0; w < width; w++)
        {
            float sum[4] = {0, 0, 0, 0};

            for (int i=0; i < kernel; i++)
            {
                for (int j=0; j < kernel; j++)
                {
                    for (int c=0; c < chan; c++)
                        sum[c] += in[i][(w + j - border)*chan + c];
                }
            }

            for (int c=0; c < chan; c++)
            {
                float result = normalize? sum[c]/(kernel * kernel) : sum[c];

                out[w*chan + c] = saturate<DST>(result, rintf);
            }
        }
    }
}

GAPI_FLUID_KERNEL(GFluidBlur, cv::gapi::imgproc::GBlur, true)
{
    static const int Window = 3;

    static void run(const View &src, const cv::Size& kernelSize, const cv::Point& anchor,
                    int /* borderType */, const cv::Scalar& /* borderValue */, Buffer &dst,
                    Buffer& scratch)
    {
        // TODO: support sizes 3, 5, 7, 9, ...
        GAPI_Assert(kernelSize.width  == 3 && kernelSize.height == 3);

        // TODO: support non-trivial anchor
        GAPI_Assert(anchor.x == -1 && anchor.y == -1);

        static const bool normalize = true;

        int width = src.length();
        int chan  = src.meta().chan;
        int length = width * chan;

        float *buf[3];
        buf[0] = scratch.OutLine<float>();
        buf[1] = buf[0] + length;
        buf[2] = buf[1] + length;

        //     DST     SRC     OP             __VA_ARGS__
        UNARY_(uchar , uchar , run_boxfilter, dst, src, kernelSize, anchor, normalize, buf);
        UNARY_(ushort, ushort, run_boxfilter, dst, src, kernelSize, anchor, normalize, buf);
        UNARY_( short,  short, run_boxfilter, dst, src, kernelSize, anchor, normalize, buf);
        UNARY_( float,  float, run_boxfilter, dst, src, kernelSize, anchor, normalize, buf);

        CV_Error(cv::Error::StsBadArg, "unsupported combination of types");
    }

    static void initScratch(const GMatDesc   & in,
                            const cv::Size   & /* ksize */,
                            const cv::Point  & /* anchor */,
                                  int          /* borderType */,
                            const cv::Scalar & /* borderValue */,
                                  Buffer     & scratch)
    {
        int width = in.size.width;
        int chan  = in.chan;

        int buflen = width * chan * Window;  // work buffers

        cv::Size bufsize(buflen, 1);
        GMatDesc bufdesc = {CV_32F, 1, bufsize};
        Buffer buffer(bufdesc);
        scratch = std::move(buffer);
    }

    static void resetScratch(Buffer& /* scratch */)
    {
    }

    static Border getBorder(const cv::GMatDesc& /* src */,
                            const cv::Size    & /* kernelSize */,
                            const cv::Point   & /* anchor */,
                                      int          borderType,
                            const cv::Scalar  &    borderValue)
    {
        return { borderType, borderValue};
    }
};

GAPI_FLUID_KERNEL(GFluidBoxFilter, cv::gapi::imgproc::GBoxFilter, true)
{
    static const int Window = 3;

    static void run(const     View  &    src,
                              int     /* ddepth */,
                    const cv::Size  &    kernelSize,
                    const cv::Point &    anchor,
                              bool       normalize,
                              int     /* borderType */,
                    const cv::Scalar& /* borderValue */,
                              Buffer&    dst,
                              Buffer&    scratch)
    {
        // TODO: support sizes 3, 5, 7, 9, ...
        GAPI_Assert(kernelSize.width  == 3 && kernelSize.height == 3);

        // TODO: support non-trivial anchor
        GAPI_Assert(anchor.x == -1 && anchor.y == -1);

        int width = src.length();
        int chan  = src.meta().chan;
        int length = width * chan;

        float *buf[3];
        buf[0] = scratch.OutLine<float>();
        buf[1] = buf[0] + length;
        buf[2] = buf[1] + length;

        //     DST     SRC     OP             __VA_ARGS__
        UNARY_(uchar , uchar , run_boxfilter, dst, src, kernelSize, anchor, normalize, buf);
        UNARY_( float, uchar , run_boxfilter, dst, src, kernelSize, anchor, normalize, buf);
        UNARY_(ushort, ushort, run_boxfilter, dst, src, kernelSize, anchor, normalize, buf);
        UNARY_( float, ushort, run_boxfilter, dst, src, kernelSize, anchor, normalize, buf);
        UNARY_( short,  short, run_boxfilter, dst, src, kernelSize, anchor, normalize, buf);
        UNARY_( float,  short, run_boxfilter, dst, src, kernelSize, anchor, normalize, buf);
        UNARY_( float,  float, run_boxfilter, dst, src, kernelSize, anchor, normalize, buf);

        CV_Error(cv::Error::StsBadArg, "unsupported combination of types");
    }

    static void initScratch(const GMatDesc  & in,
                                      int     /* ddepth */,
                            const cv::Size  & /* kernelSize */,
                            const cv::Point & /* anchor */,
                                      bool    /*  normalize */,
                                      int     /* borderType */,
                            const cv::Scalar& /* borderValue */,
                                  Buffer    &  scratch)
    {
        int width = in.size.width;
        int chan  = in.chan;

        int buflen = width * chan * Window;  // work buffers

        cv::Size bufsize(buflen, 1);
        GMatDesc bufdesc = {CV_32F, 1, bufsize};
        Buffer buffer(bufdesc);
        scratch = std::move(buffer);
    }

    static void resetScratch(Buffer& /* scratch */)
    {
    }

    static Border getBorder(const cv::GMatDesc& /* src */,
                                      int       /* ddepth */,
                            const cv::Size    & /* kernelSize */,
                            const cv::Point   & /* anchor */,
                                      bool      /* normalize */,
                                      int          borderType,
                            const cv::Scalar  &    borderValue)
    {
        return { borderType, borderValue};
    }
};

//-------------------------
//
// Fluid kernels: sepFilter
//
//-------------------------

template<typename T>
static void getKernel(T k[], const cv::Mat& kernel)
{
    GAPI_Assert(kernel.channels() == 1);

    int depth = CV_MAT_DEPTH(kernel.type());
    int cols = kernel.cols;
    int rows = kernel.rows;

    switch ( depth )
    {
    case CV_8U:
        for (int h=0; h < rows; h++)
        for (int w=0; w < cols; w++)
            k[h*cols + w] = static_cast<T>( kernel.at<uchar>(h, w) );
        break;
    case CV_16U:
        for (int h=0; h < rows; h++)
        for (int w=0; w < cols; w++)
            k[h*cols + w] = static_cast<T>( kernel.at<ushort>(h, w) );
        break;
    case CV_16S:
        for (int h=0; h < rows; h++)
        for (int w=0; w < cols; w++)
            k[h*cols + w] = static_cast<T>( kernel.at<short>(h, w) );
        break;
    case CV_32F:
        for (int h=0; h < rows; h++)
        for (int w=0; w < cols; w++)
            k[h*cols + w] = static_cast<T>( kernel.at<float>(h, w) );
        break;
    default: CV_Error(cv::Error::StsBadArg, "unsupported kernel type");
    }
}

template<typename DST, typename SRC>
static void run_sepfilter(Buffer& dst, const View& src,
                          const float kx[], int kxLen,
                          const float ky[], int kyLen,
                          const cv::Point& /* anchor */,
                          float scale, float delta,
                          float *buf[])
{
    constexpr int kMax = 11;
    GAPI_Assert(kxLen <= kMax && kyLen <= kMax);
    GAPI_Assert(kxLen == kyLen);

    const SRC *in[kMax];
          DST *out;

    int xborder = (kxLen - 1) / 2;
    int yborder = (kyLen - 1) / 2;

    for (int i=0; i < kyLen; i++)
    {
        in[i] = src.InLine<SRC>(i - yborder);
    }

    out = dst.OutLine<DST>();

    int width = dst.length();
    int chan  = dst.meta().chan;

    // optimized 3x3 vs reference
    if (kxLen == 3 && kyLen == 3)
    {
        int y  = dst.y();
        int y0 = dst.priv().writeStart();

        int border = xborder;
        run_sepfilter3x3_impl(out, in, width, chan, kx, ky, border, scale, delta, buf, y, y0);
    }
    else if (kxLen == 5 && kyLen == 5)
    {
        int y = dst.y();
        int y0 = dst.priv().writeStart();

        run_sepfilter5x5_impl(out, in, width, chan, kx, ky, xborder, scale, delta, buf, y, y0);
    }
    else
    {
        int length = chan * width;
        int xshift = chan;

        // horizontal pass

        for (int k=0; k < kyLen; k++)
        {
            const SRC *inp[kMax] = {nullptr};

            for (int j=0; j < kxLen; j++)
            {
                inp[j] = in[k] + (j - xborder)*xshift;
            }

            for (int l=0; l < length; l++)
            {
                float sum = 0;
                for (int j=0; j < kxLen; j++)
                {
                    sum += inp[j][l] * kx[j];
                }
                buf[k][l] = sum;
            }
        }

        // vertical pass

        for (int l=0; l < length; l++)
        {
            float sum = 0;
            for (int k=0; k < kyLen; k++)
            {
                sum += buf[k][l] * ky[k];
            }
            out[l] = saturate<DST>(sum*scale + delta, rintf);
        }
    }
}

GAPI_FLUID_KERNEL(GFluidSepFilter, cv::gapi::imgproc::GSepFilter, true)
{
    static const int Window = 3;

    static void run(const     View&      src,
                              int     /* ddepth */,
                    const cv::Mat&       kernX,
                    const cv::Mat&       kernY,
                    const cv::Point&     anchor,
                    const cv::Scalar&    delta_,
                              int     /* borderType */,
                    const cv::Scalar& /* borderValue */,
                              Buffer&    dst,
                              Buffer&    scratch)
    {
        // TODO: support non-trivial anchors
        GAPI_Assert(anchor.x == -1 && anchor.y == -1);

        // TODO: support kernel heights 3, 5, 7, 9, ...
        GAPI_Assert((kernY.rows == 1 || kernY.cols == 1)  && (kernY.cols * kernY.rows == 3));
        GAPI_Assert((kernX.rows == 1 || kernX.cols == 1));

        int kxLen = kernX.rows * kernX.cols;
        int kyLen = kernY.rows * kernY.cols;

        GAPI_Assert(kyLen == 3);

        float *kx = scratch.OutLine<float>();
        float *ky = kx + kxLen;

        int width = src.meta().size.width;
        int chan  = src.meta().chan;
        int length = width * chan;

        float *buf[3];
        buf[0] = ky + kyLen;
        buf[1] = buf[0] + length;
        buf[2] = buf[1] + length;

        float scale = 1;
        float delta = static_cast<float>(delta_[0]);

        //     DST     SRC     OP             __VA_ARGS__
        UNARY_(uchar , uchar , run_sepfilter, dst, src, kx, kxLen, ky, kyLen, anchor, scale, delta, buf);
        UNARY_( short, uchar , run_sepfilter, dst, src, kx, kxLen, ky, kyLen, anchor, scale, delta, buf);
        UNARY_( float, uchar , run_sepfilter, dst, src, kx, kxLen, ky, kyLen, anchor, scale, delta, buf);
        UNARY_(ushort, ushort, run_sepfilter, dst, src, kx, kxLen, ky, kyLen, anchor, scale, delta, buf);
        UNARY_( float, ushort, run_sepfilter, dst, src, kx, kxLen, ky, kyLen, anchor, scale, delta, buf);
        UNARY_( short,  short, run_sepfilter, dst, src, kx, kxLen, ky, kyLen, anchor, scale, delta, buf);
        UNARY_( float,  short, run_sepfilter, dst, src, kx, kxLen, ky, kyLen, anchor, scale, delta, buf);
        UNARY_( float,  float, run_sepfilter, dst, src, kx, kxLen, ky, kyLen, anchor, scale, delta, buf);

        CV_Error(cv::Error::StsBadArg, "unsupported combination of types");
    }

    static void initScratch(const GMatDesc&    in,
                                  int       /* ddepth */,
                            const Mat     &    kernX,
                            const Mat     &    kernY,
                            const Point   & /* anchor */,
                            const Scalar  & /* delta */,
                                  int       /* borderType */,
                            const Scalar  & /* borderValue */,
                                  Buffer  &    scratch)
    {
        int kxLen = kernX.rows * kernX.cols;
        int kyLen = kernY.rows * kernY.cols;

        int width = in.size.width;
        int chan  = in.chan;

        int buflen = kxLen + kyLen +         // x, y kernels
                     width * chan * Window;  // work buffers

        cv::Size bufsize(buflen, 1);
        GMatDesc bufdesc = {CV_32F, 1, bufsize};
        Buffer buffer(bufdesc);
        scratch = std::move(buffer);

        // FIXME: move to resetScratch stage ?
        float *kx = scratch.OutLine<float>();
        float *ky = kx + kxLen;
        getKernel(kx, kernX);
        getKernel(ky, kernY);
    }

    static void resetScratch(Buffer& /* scratch */)
    {
    }

    static Border getBorder(const cv::GMatDesc& /* src */,
                                      int       /* ddepth */,
                            const cv::Mat&      /* kernX */,
                            const cv::Mat&      /* kernY */,
                            const cv::Point&    /* anchor */,
                            const cv::Scalar&   /* delta */,
                                      int          borderType,
                            const cv::Scalar&      borderValue)
    {
        return { borderType, borderValue};
    }
};

//----------------------------
//
// Fluid kernels: gaussianBlur
//
//----------------------------

GAPI_FLUID_KERNEL(GFluidGaussBlur, cv::gapi::imgproc::GGaussBlur, true)
{
    // TODO: support kernel height 3, 5, 7, 9, ...

    static void run(const     View  &    src,
                    const cv::Size  &    ksize,
                              double  /* sigmaX */,
                              double  /* sigmaY */,
                              int     /* borderType */,
                    const cv::Scalar& /* borderValue */,
                              Buffer&    dst,
                              Buffer&    scratch)
    {
        GAPI_Assert(ksize.height == ksize.width);
        GAPI_Assert((ksize.height == 3) || (ksize.height == 5));
        const int kxsize = ksize.width;
        int kysize = ksize.height;

        auto *kx = scratch.OutLine<float>(); // cached kernX data
        auto *ky = kx + kxsize;              // cached kernY data

        int width = src.meta().size.width;
        int chan  = src.meta().chan;
        int length = width * chan;

        constexpr int buffSize = 5;
        GAPI_Assert(ksize.height <= buffSize);

        float *buf[buffSize] = { nullptr };

        buf[0] = ky + kysize;
        for (int i = 1; i < ksize.height; ++i)
        {
            buf[i] = buf[i - 1] + length;
        }

        auto  anchor = cv::Point(-1, -1);

        float scale = 1;
        float delta = 0;

        //     DST     SRC     OP             __VA_ARGS__
        UNARY_(uchar , uchar , run_sepfilter, dst, src, kx, kxsize, ky, kysize, anchor, scale, delta, buf);
        UNARY_(ushort, ushort, run_sepfilter, dst, src, kx, kxsize, ky, kysize, anchor, scale, delta, buf);
        UNARY_( short,  short, run_sepfilter, dst, src, kx, kxsize, ky, kysize, anchor, scale, delta, buf);
        UNARY_( float,  float, run_sepfilter, dst, src, kx, kxsize, ky, kysize, anchor, scale, delta, buf);

        CV_Error(cv::Error::StsBadArg, "unsupported combination of types");
    }

    static void initScratch(const GMatDesc&    in,
                            const cv::Size &   ksize,
                                  double       sigmaX,
                                  double       sigmaY,
                                  int          /* borderType */,
                            const cv::Scalar & /* borderValue */,
                                  Buffer  &    scratch)
    {
        GAPI_Assert(ksize.height == ksize.width);
        int kxsize = ksize.width;
        int kysize = ksize.height;

        int width = in.size.width;
        int chan  = in.chan;

        int buflen = kxsize + kysize +       // x, y kernels
                     width * chan * ksize.height;  // work buffers

        cv::Size bufsize(buflen, 1);
        GMatDesc bufdesc = {CV_32F, 1, bufsize};
        Buffer buffer(bufdesc);
        scratch = std::move(buffer);

        // FIXME: fill buffer at resetScratch stage?

        if (sigmaX == 0)
            sigmaX = 0.3 * ((kxsize - 1)/2. - 1) + 0.8;

        if (sigmaY == 0)
            sigmaY = sigmaX;

        Mat kernX = getGaussianKernel(kxsize, sigmaX, CV_32F);

        Mat kernY = kernX;
        if (sigmaY != sigmaX)
            kernY = getGaussianKernel(kysize, sigmaY, CV_32F);

        auto *kx = scratch.OutLine<float>();
        auto *ky = kx + kxsize;

        getKernel(kx, kernX);
        getKernel(ky, kernY);
    }

    static void resetScratch(Buffer& /* scratch */)
    {
    }

    static Border getBorder(const cv::GMatDesc& /* src */,
                            const cv::Size    & /* ksize */,
                                      double    /* sigmaX */,
                                      double    /* sigmaY */,
                                      int          borderType,
                            const cv::Scalar  &    borderValue)
    {
        return { borderType, borderValue};
    }

    static int getWindow(const cv::GMatDesc& /* src */,
                         const cv::Size&        ksize,
                         double              /* sigmaX */,
                         double              /* sigmaY */,
                         int                 /* borderType */,
                         const cv::Scalar&   /* borderValue */)
    {
        GAPI_Assert(ksize.height == ksize.width);
        return ksize.height;
    }
};

//---------------------
//
// Fluid kernels: Sobel
//
//---------------------

template<typename DST, typename SRC>
static void run_sobel(Buffer& dst,
                const View  & src,
                const float   kx[],
                const float   ky[],
                      int     ksize,
                      float   scale,  // default: 1
                      float   delta,  // default: 0
                      float  *buf[])
{
    static const int kmax = 11;
    GAPI_Assert(ksize <= kmax);

    const SRC *in[ kmax ];
          DST *out;

    int border = (ksize - 1) / 2;
    for (int i=0; i < ksize; i++)
    {
        in[i] = src.InLine<SRC>(i - border);
    }

    out = dst.OutLine<DST>();

    int width = dst.length();
    int chan  = dst.meta().chan;

    GAPI_DbgAssert(ksize == 3);
//  float buf[3][width * chan];

    int y  = dst.y();
    int y0 = dst.priv().writeStart();
//  int y1 = dst.priv().writeEnd();

    run_sepfilter3x3_impl(out, in, width, chan, kx, ky, border, scale, delta, buf, y, y0);
}

GAPI_FLUID_KERNEL(GFluidSobel, cv::gapi::imgproc::GSobel, true)
{
    static const int Window = 3;

    static void run(const     View  &    src,
                              int     /* ddepth */,
                              int     /* dx */,
                              int     /* dy */,
                              int        ksize,
                              double    _scale,
                              double    _delta,
                              int     /* borderType */,
                    const cv::Scalar& /* borderValue */,
                              Buffer&    dst,
                              Buffer&    scratch)
    {
        // TODO: support kernel height 3, 5, 7, 9, ...
        GAPI_Assert(ksize == 3 || ksize == FILTER_SCHARR);

        int ksz = (ksize == FILTER_SCHARR)? 3: ksize;

        auto *kx = scratch.OutLine<float>();
        auto *ky = kx + ksz;

        int width = dst.meta().size.width;
        int chan  = dst.meta().chan;

        float *buf[3];
        buf[0] = ky + ksz;
        buf[1] = buf[0] + width*chan;
        buf[2] = buf[1] + width*chan;

        auto scale = static_cast<float>(_scale);
        auto delta = static_cast<float>(_delta);

        //     DST     SRC     OP         __VA_ARGS__
        UNARY_(uchar , uchar , run_sobel, dst, src, kx, ky, ksz, scale, delta, buf);
        UNARY_(ushort, ushort, run_sobel, dst, src, kx, ky, ksz, scale, delta, buf);
        UNARY_( short, uchar , run_sobel, dst, src, kx, ky, ksz, scale, delta, buf);
        UNARY_( short, ushort, run_sobel, dst, src, kx, ky, ksz, scale, delta, buf);
        UNARY_( short,  short, run_sobel, dst, src, kx, ky, ksz, scale, delta, buf);
        UNARY_( float, uchar , run_sobel, dst, src, kx, ky, ksz, scale, delta, buf);
        UNARY_( float, ushort, run_sobel, dst, src, kx, ky, ksz, scale, delta, buf);
        UNARY_( float,  short, run_sobel, dst, src, kx, ky, ksz, scale, delta, buf);
        UNARY_( float,  float, run_sobel, dst, src, kx, ky, ksz, scale, delta, buf);

        CV_Error(cv::Error::StsBadArg, "unsupported combination of types");
    }

    static void initScratch(const GMatDesc&    in,
                                  int       /* ddepth */,
                                  int          dx,
                                  int          dy,
                                  int          ksize,
                                  double    /* scale */,
                                  double    /* delta */,
                                  int       /* borderType */,
                            const Scalar  & /* borderValue */,
                                  Buffer  &    scratch)
    {
        // TODO: support kernel height 3, 5, 7, 9, ...
        GAPI_Assert(ksize == 3 || ksize == FILTER_SCHARR);
        int ksz = (ksize == FILTER_SCHARR) ? 3 : ksize;

        int width = in.size.width;
        int chan  = in.chan;

        int buflen = ksz + ksz            // kernels: kx, ky
                   + ksz * width * chan;  // working buffers

        cv::Size bufsize(buflen, 1);
        GMatDesc bufdesc = {CV_32F, 1, bufsize};
        Buffer buffer(bufdesc);
        scratch = std::move(buffer);

        auto *kx = scratch.OutLine<float>();
        auto *ky = kx + ksz;

        Mat kxmat(1, ksize, CV_32FC1, kx);
        Mat kymat(ksize, 1, CV_32FC1, ky);
        getDerivKernels(kxmat, kymat, dx, dy, ksize);
    }

    static void resetScratch(Buffer& /* scratch */)
    {
    }

    static Border getBorder(const cv::GMatDesc& /* src */,
                                      int       /* ddepth */,
                                      int       /* dx */,
                                      int       /* dy */,
                                      int       /* ksize */,
                                      double    /* scale */,
                                      double    /* delta */,
                                      int          borderType,
                            const cv::Scalar  &    borderValue)
    {
        return {borderType, borderValue};
    }
};

//---------------------
//
// Fluid kernels: SobelXY
//
//---------------------

GAPI_FLUID_KERNEL(GFluidSobelXY, cv::gapi::imgproc::GSobelXY, true)
{
    static const int Window = 3;

    struct BufHelper
    {
        float *kx_dx, *ky_dx,
              *kx_dy, *ky_dy;
        float *buf_start;
        int buf_width, buf_chan;

        static int length(int ksz, int width, int chan)
        {
            return ksz + ksz + ksz + ksz    // kernels: kx_dx, ky_dx, kx_dy, ky_dy
                   + 2 * ksz * width * chan;
        }

        BufHelper(int ksz, int width, int chan, Buffer& scratch)
        {
            kx_dx = scratch.OutLine<float>();
            ky_dx = kx_dx + ksz;
            kx_dy = ky_dx + ksz;
            ky_dy = kx_dy + ksz;
            buf_start = ky_dy + ksz;
            buf_width = width;
            buf_chan = chan;
        }

        float* operator [](int i) {
            return buf_start + i *  buf_width * buf_chan;
        }
    };

    static void run(const     View  &    in,
                              int     /* ddepth */,
                              int     /* order */,
                              int        ksize,
                              double    _scale,
                              double    _delta,
                              int     /* borderType */,
                    const cv::Scalar& /* borderValue */,
                              Buffer&    out_x,
                              Buffer&    out_y,
                              Buffer&    scratch)
    {
        // TODO: support kernel height 3, 5, 7, 9, ...
        GAPI_Assert(ksize == 3 || ksize == FILTER_SCHARR);

        int ksz = (ksize == FILTER_SCHARR)? 3: ksize;

        GAPI_Assert(out_x.meta().size.width == out_y.meta().size.width);
        GAPI_Assert(out_x.meta().chan == out_y.meta().chan);

        int width = out_x.meta().size.width;
        int chan  = out_x.meta().chan;

        BufHelper buf_helper(ksz, width, chan, scratch);

        auto *kx_dx = buf_helper.kx_dx;
        auto *ky_dx = buf_helper.ky_dx;
        auto *kx_dy = buf_helper.kx_dy;
        auto *ky_dy = buf_helper.ky_dy;

        // Scratch buffer layout:
        // |kx_dx|ky_dx|kx_dy|ky_dy|3 lines for horizontal kernel|3 lines for vertical kernel|
        float *buf[3];
        buf[0] = buf_helper[0];
        buf[1] = buf_helper[1];
        buf[2] = buf_helper[2];

        auto scale = static_cast<float>(_scale);
        auto delta = static_cast<float>(_delta);

        auto calc = [&](const View& src, Buffer& dst, float* kx, float* ky) {
            //     DST     SRC     OP         __VA_ARGS__
            UNARY_(uchar , uchar , run_sobel, dst, src, kx, ky, ksz, scale, delta, buf);
            UNARY_(ushort, ushort, run_sobel, dst, src, kx, ky, ksz, scale, delta, buf);
            UNARY_( short, uchar , run_sobel, dst, src, kx, ky, ksz, scale, delta, buf);
            UNARY_( short, ushort, run_sobel, dst, src, kx, ky, ksz, scale, delta, buf);
            UNARY_( short,  short, run_sobel, dst, src, kx, ky, ksz, scale, delta, buf);
            UNARY_( float, uchar , run_sobel, dst, src, kx, ky, ksz, scale, delta, buf);
            UNARY_( float, ushort, run_sobel, dst, src, kx, ky, ksz, scale, delta, buf);
            UNARY_( float,  short, run_sobel, dst, src, kx, ky, ksz, scale, delta, buf);
            UNARY_( float,  float, run_sobel, dst, src, kx, ky, ksz, scale, delta, buf);

            CV_Error(cv::Error::StsBadArg, "unsupported combination of types");
        };

        // calculate x-derivative
        calc(in, out_x, kx_dx, ky_dx);

        // Move pointers to calculate dy(preventing buffer data corruption)
        buf[0] = buf_helper[3];
        buf[1] = buf_helper[4];
        buf[2] = buf_helper[5];

        // calculate y-derivative
        calc(in, out_y, kx_dy, ky_dy);
    }

    static void initScratch(const GMatDesc&    in,
                                  int       /* ddepth */,
                                  int          order,
                                  int          ksize,
                                  double    /* scale */,
                                  double    /* delta */,
                                  int       /* borderType */,
                            const Scalar  & /* borderValue */,
                                  Buffer  &    scratch)
    {
        // TODO: support kernel height 3, 5, 7, 9, ...
        GAPI_Assert(ksize == 3 || ksize == FILTER_SCHARR);
        int ksz = (ksize == FILTER_SCHARR) ? 3 : ksize;

        int width = in.size.width;
        int chan  = in.chan;
        int buflen = BufHelper::length(ksz, width, chan);

        cv::Size bufsize(buflen, 1);
        GMatDesc bufdesc = {CV_32F, 1, bufsize};
        Buffer buffer(bufdesc);
        scratch = std::move(buffer);

        BufHelper buf_helper(ksz, width, chan, scratch);

        auto *kx_dx = buf_helper.kx_dx;
        auto *ky_dx = buf_helper.ky_dx;
        auto *kx_dy = buf_helper.kx_dy;
        auto *ky_dy = buf_helper.ky_dy;

        Mat kxmatX(1, ksize, CV_32FC1, kx_dx);
        Mat kymatX(ksize, 1, CV_32FC1, ky_dx);
        getDerivKernels(kxmatX, kymatX, order, 0, ksize);

        Mat kxmatY(1, ksize, CV_32FC1, kx_dy);
        Mat kymatY(ksize, 1, CV_32FC1, ky_dy);
        getDerivKernels(kxmatY, kymatY, 0, order, ksize);
    }

    static void resetScratch(Buffer& /* scratch */)
    {
    }

    static Border getBorder(const cv::GMatDesc& /* src */,
                                      int       /* ddepth */,
                                      int       /* order */,
                                      int       /* ksize */,
                                      double    /* scale */,
                                      double    /* delta */,
                                      int          borderType,
                            const cv::Scalar  &    borderValue)
    {
        return {borderType, borderValue};
    }
};

//------------------------
//
// Fluid kernels: filter2D
//
//------------------------

template<typename DST, typename SRC>
static void run_filter2d(Buffer& dst, const View& src,
                         const float k[], int k_rows, int k_cols,
                         const cv::Point& /* anchor */,
                         float delta=0)
{
    static const int maxLines = 9;
    GAPI_Assert(k_rows <= maxLines);

    const SRC *in[ maxLines ];
          DST *out;

    int border_x = (k_cols - 1) / 2;
    int border_y = (k_rows - 1) / 2;

    for (int i=0; i < k_rows; i++)
    {
        in[i] = src.InLine<SRC>(i - border_y);
    }

    out = dst.OutLine<DST>();

    int width = dst.length();
    int chan  = dst.meta().chan;
    int length = width * chan;

    // manually optimized for 3x3
    if (k_rows == 3 && k_cols == 3)
    {
        float scale = 1;
        run_filter2d_3x3_impl(out, in, width, chan, k, scale, delta);
        return;
    }

    // reference: any kernel size
    for (int l=0; l < length; l++)
    {
        float sum = 0;

        for (int i=0; i < k_rows; i++)
        for (int j=0; j < k_cols; j++)
        {
            sum += in[i][l + (j - border_x)*chan] * k[k_cols*i + j];
        }

        float result = sum + delta;

        out[l] = saturate<DST>(result, rintf);
    }
}

GAPI_FLUID_KERNEL(GFluidFilter2D, cv::gapi::imgproc::GFilter2D, true)
{
    static const int Window = 3;

    static void run(const     View  &    src,
                              int     /* ddepth */,
                    const cv::Mat   &    kernel,
                    const cv::Point &    anchor,
                    const cv::Scalar&    delta_,
                              int     /* borderType */,
                    const cv::Scalar& /* borderValue */,
                              Buffer&    dst,
                              Buffer&    scratch)
    {
        // TODO: support non-trivial anchors
        GAPI_Assert(anchor.x == -1 && anchor.y == -1);

        // TODO: support kernel heights 3, 5, 7, 9, ...
        GAPI_Assert(kernel.rows == 3 && kernel.cols == 3);

        float delta = static_cast<float>(delta_[0]);

        int k_rows = kernel.rows;
        int k_cols = kernel.cols;

        const float *k = scratch.OutLine<float>(); // copy of kernel.data

        //     DST     SRC     OP            __VA_ARGS__
        UNARY_(uchar , uchar , run_filter2d, dst, src, k, k_rows, k_cols, anchor, delta);
        UNARY_(ushort, ushort, run_filter2d, dst, src, k, k_rows, k_cols, anchor, delta);
        UNARY_( short,  short, run_filter2d, dst, src, k, k_rows, k_cols, anchor, delta);
        UNARY_( float, uchar , run_filter2d, dst, src, k, k_rows, k_cols, anchor, delta);
        UNARY_( float, ushort, run_filter2d, dst, src, k, k_rows, k_cols, anchor, delta);
        UNARY_( float,  short, run_filter2d, dst, src, k, k_rows, k_cols, anchor, delta);
        UNARY_( float,  float, run_filter2d, dst, src, k, k_rows, k_cols, anchor, delta);

        CV_Error(cv::Error::StsBadArg, "unsupported combination of types");
    }

    static void initScratch(const cv::GMatDesc& /* in */,
                                      int       /* ddepth */,
                            const cv::Mat     &    kernel,
                            const cv::Point   & /* anchor */,
                            const cv::Scalar  & /* delta */,
                                      int       /* borderType */,
                            const cv::Scalar  & /* borderValue */,
                                      Buffer  &    scratch)
    {
        int krows = kernel.rows;
        int kcols = kernel.cols;

        int buflen = krows * kcols;  // kernel size

        cv::Size bufsize(buflen, 1);
        GMatDesc bufdesc = {CV_32F, 1, bufsize};
        Buffer buffer(bufdesc);
        scratch = std::move(buffer);

        // FIXME: move to resetScratch stage ?
        float *data = scratch.OutLine<float>();
        getKernel(data, kernel);
    }

    static void resetScratch(Buffer& /* scratch */)
    {
    }

    static Border getBorder(const cv::GMatDesc& /* src */,
                                      int       /* ddepth */,
                            const cv::Mat&      /* kernel */,
                            const cv::Point&    /* anchor */,
                            const cv::Scalar&   /* delta */,
                                      int          borderType,
                            const cv::Scalar&      borderValue)
    {
        return { borderType, borderValue};
    }
};

//-----------------------------
//
// Fluid kernels: erode, dilate
//
//-----------------------------

static MorphShape detect_morph3x3_shape(const uchar kernel[])
{
    const uchar k[3][3] = {
        { kernel[0], kernel[1], kernel[2]},
        { kernel[3], kernel[4], kernel[5]},
        { kernel[6], kernel[7], kernel[8]}
    };

    if (k[0][0] && k[0][1] && k[0][2] &&
        k[1][0] && k[1][1] && k[1][2] &&
        k[2][0] && k[2][1] && k[2][2])
        return M_FULL;

    if (!k[0][0] && k[0][1] && !k[0][2] &&
         k[1][0] && k[1][1] &&  k[1][2] &&
        !k[2][0] && k[2][1] && !k[2][2])
        return M_CROSS;

    return M_UNDEF;
}

template<typename DST, typename SRC>
static void run_morphology(          Buffer&    dst,
                           const     View  &    src,
                           const     uchar      k[],
                                     int        k_rows,
                                     int        k_cols,
                                     MorphShape k_type,
                           const cv::Point & /* anchor */,
                                     Morphology morphology)
{
    static_assert(std::is_same<DST, SRC>::value, "unsupported combination of types");

    GAPI_Assert(M_ERODE == morphology || M_DILATE == morphology);

    static const int maxLines = 9;
    GAPI_Assert(k_rows <= maxLines);

    const SRC *in[ maxLines ];
          DST *out;

    int border_x = (k_cols - 1) / 2;
    int border_y = (k_rows - 1) / 2;

    for (int i=0; i < k_rows; i++)
    {
        in[i] = src.InLine<SRC>(i - border_y);
    }

    out = dst.OutLine<DST>();

    int width = dst.length();
    int chan  = dst.meta().chan;

    // call optimized code, if 3x3
    if (3 == k_rows && 3 == k_cols)
    {
        run_morphology3x3_impl(out, in, width, chan, k, k_type, morphology);
        return;
    }

    // reference: any size of k[]
    int length = width * chan;
    for (int l=0; l < length; l++)
    {
        SRC result;
        if (M_ERODE == morphology)
        {
            result = std::numeric_limits<SRC>::max();
        }
        else // if (M_DILATE == morphology)
        {
            result = std::numeric_limits<SRC>::min();
        }

        for (int i=0; i < k_rows; i++)
        for (int j=0; j < k_cols; j++)
        {
            if ( k[k_cols*i + j] )
            {
                if (M_ERODE == morphology)
                {
                    result = (std::min)(result, in[i][l + (j - border_x)*chan]);
                }
                else // if (M_DILATE == morphology)
                {
                    result = (std::max)(result, in[i][l + (j - border_x)*chan]);
                }
            }
        }

        out[l] = saturate<DST>(result, rintf);
    }
}

GAPI_FLUID_KERNEL(GFluidErode, cv::gapi::imgproc::GErode, true)
{
    static const int Window = 3;

    static void run(const     View  &    src,
                    const cv::Mat   &    kernel,
                    const cv::Point &    anchor,
                              int        iterations,
                              int     /* borderType */,
                    const cv::Scalar& /* borderValue */,
                              Buffer&    dst,
                              Buffer&    scratch)
    {
        // TODO: support non-trivial anchors
        GAPI_Assert(anchor.x == -1 && anchor.y == -1);

        // TODO: support kernel heights 3, 5, 7, 9, ...
        GAPI_Assert(kernel.rows == 3 && kernel.cols == 3);

        // TODO: support iterations > 1
        GAPI_Assert(iterations == 1);

        int k_rows = kernel.rows;
        int k_cols = kernel.cols;
        int k_size = k_rows * k_cols;

        auto *k = scratch.OutLine<uchar>(); // copy of kernel.data
        auto k_type = static_cast<MorphShape>(k[k_size]);

        //     DST     SRC     OP              __VA_ARGS__
        UNARY_(uchar , uchar , run_morphology, dst, src, k, k_rows, k_cols, k_type, anchor, M_ERODE);
        UNARY_(ushort, ushort, run_morphology, dst, src, k, k_rows, k_cols, k_type, anchor, M_ERODE);
        UNARY_( short,  short, run_morphology, dst, src, k, k_rows, k_cols, k_type, anchor, M_ERODE);
        UNARY_( float,  float, run_morphology, dst, src, k, k_rows, k_cols, k_type, anchor, M_ERODE);

        CV_Error(cv::Error::StsBadArg, "unsupported combination of types");
    }

    static void initScratch(const GMatDesc& /* in */,
                            const Mat     &    kernel,
                            const Point   & /* anchor */,
                                  int       /* iterations */,
                                  int       /* borderType */,
                            const cv::Scalar  & /* borderValue */,
                                  Buffer  &    scratch)
    {
        int k_rows = kernel.rows;
        int k_cols = kernel.cols;
        int k_size = k_rows * k_cols;

        cv::Size bufsize(k_size + 1, 1);
        GMatDesc bufdesc = {CV_8U, 1, bufsize};
        Buffer buffer(bufdesc);
        scratch = std::move(buffer);

        // FIXME: move to resetScratch stage ?
        auto *k = scratch.OutLine<uchar>();
        getKernel(k, kernel);

        if (3 == k_rows && 3 == k_cols)
            k[k_size] = static_cast<uchar>(detect_morph3x3_shape(k));
        else
            k[k_size] = static_cast<uchar>(M_UNDEF);
    }

    static void resetScratch(Buffer& /* scratch */)
    {
    }

    static Border getBorder(const cv::GMatDesc& /* src */,
                            const cv::Mat   &   /* kernel */,
                            const cv::Point &   /* anchor */,
                                      int       /* iterations */,
                                      int          borderType,
                            const cv::Scalar&      borderValue)
    {
    #if 1
        // TODO: saturate borderValue to image type in general case (not only maximal border)
        GAPI_Assert(borderType == cv::BORDER_CONSTANT && borderValue[0] == DBL_MAX);
        return { borderType, cv::Scalar::all(INT_MAX) };
    #else
        return { borderType, borderValue };
    #endif
    }
};

GAPI_FLUID_KERNEL(GFluidDilate, cv::gapi::imgproc::GDilate, true)
{
    static const int Window = 3;

    static void run(const     View  &    src,
                    const cv::Mat   &    kernel,
                    const cv::Point &    anchor,
                              int        iterations,
                              int     /* borderType */,
                    const cv::Scalar& /* borderValue */,
                              Buffer&    dst,
                              Buffer&    scratch)
    {
        // TODO: support non-trivial anchors
        GAPI_Assert(anchor.x == -1 && anchor.y == -1);

        // TODO: support kernel heights 3, 5, 7, 9, ...
        GAPI_Assert(kernel.rows == 3 && kernel.cols == 3);

        // TODO: support iterations > 1
        GAPI_Assert(iterations == 1);

        int k_rows = kernel.rows;
        int k_cols = kernel.cols;
        int k_size = k_rows * k_cols;

        auto *k = scratch.OutLine<uchar>(); // copy of kernel.data
        auto k_type = static_cast<MorphShape>(k[k_size]);

        //     DST     SRC     OP              __VA_ARGS__
        UNARY_(uchar , uchar , run_morphology, dst, src, k, k_rows, k_cols, k_type, anchor, M_DILATE);
        UNARY_(ushort, ushort, run_morphology, dst, src, k, k_rows, k_cols, k_type, anchor, M_DILATE);
        UNARY_( short,  short, run_morphology, dst, src, k, k_rows, k_cols, k_type, anchor, M_DILATE);
        UNARY_( float,  float, run_morphology, dst, src, k, k_rows, k_cols, k_type, anchor, M_DILATE);

        CV_Error(cv::Error::StsBadArg, "unsupported combination of types");
    }

    static void initScratch(const GMatDesc& /* in */,
                            const Mat     &    kernel,
                            const Point   & /* anchor */,
                              int           /* iterations */,
                                  int       /* borderType */,
                            const cv::Scalar  & /* borderValue */,
                                  Buffer  &    scratch)
    {
        int k_rows = kernel.rows;
        int k_cols = kernel.cols;
        int k_size = k_rows * k_cols;

        cv::Size bufsize(k_size + 1, 1);
        GMatDesc bufdesc = {CV_8U, 1, bufsize};
        Buffer buffer(bufdesc);
        scratch = std::move(buffer);

        // FIXME: move to resetScratch stage ?
        auto *k = scratch.OutLine<uchar>();
        getKernel(k, kernel);

        if (3 == k_rows && 3 == k_cols)
            k[k_size] = static_cast<uchar>(detect_morph3x3_shape(k));
        else
            k[k_size] = static_cast<uchar>(M_UNDEF);
    }

    static void resetScratch(Buffer& /* scratch */)
    {
    }

    static Border getBorder(const cv::GMatDesc& /* src */,
                            const cv::Mat   &   /* kernel */,
                            const cv::Point &   /* anchor */,
                                      int       /* iterations */,
                                      int       borderType,
                            const cv::Scalar&   borderValue)
    {
    #if 1
        // TODO: fix borderValue for Dilate in general case (not only minimal border)
        GAPI_Assert(borderType == cv::BORDER_CONSTANT && borderValue[0] == DBL_MAX);
        return { borderType, cv::Scalar::all(INT_MIN) };
    #else
        return { borderType, borderValue };
    #endif
    }
};

//--------------------------
//
// Fluid kernels: medianBlur
//
//--------------------------

template<typename DST, typename SRC>
static void run_medianblur(      Buffer& dst,
                           const View  & src,
                                 int     ksize)
{
    static_assert(std::is_same<DST, SRC>::value, "unsupported combination of types");

    constexpr int kmax = 9;
    GAPI_Assert(ksize <= kmax);

    const SRC *in[ kmax ];
          DST *out;

    int border = (ksize - 1) / 2;

    for (int i=0; i < ksize; i++)
    {
        in[i] = src.InLine<SRC>(i - border);
    }

    out = dst.OutLine<DST>(0);

    int width = dst.length();
    int chan  = dst.meta().chan;

    // optimized: if 3x3

    if (3 == ksize)
    {
        run_medblur3x3_impl(out, in, width, chan);
        return;
    }

    // reference: any ksize

    int length = width * chan;
    int klength = ksize * ksize;
    int klenhalf = klength / 2;

    for (int l=0; l < length; l++)
    {
        SRC neighbours[kmax * kmax];

        for (int i=0; i < ksize; i++)
        for (int j=0; j < ksize; j++)
        {
            neighbours[i*ksize + j] = in[i][l + (j - border)*chan];
        }

        std::nth_element(neighbours, neighbours + klenhalf, neighbours + klength);

        out[l] = saturate<DST>(neighbours[klenhalf], rintf);
    }
}

GAPI_FLUID_KERNEL(GFluidMedianBlur, cv::gapi::imgproc::GMedianBlur, false)
{
    static const int Window = 3;

    static void run(const View  & src,
                          int     ksize,
                          Buffer& dst)
    {
        // TODO: support kernel sizes: 3, 5, 7, 9, ...
        GAPI_Assert(ksize == 3);

        //     DST     SRC     OP              __VA_ARGS__
        UNARY_(uchar , uchar , run_medianblur, dst, src, ksize);
        UNARY_(ushort, ushort, run_medianblur, dst, src, ksize);
        UNARY_( short,  short, run_medianblur, dst, src, ksize);
        UNARY_( float,  float, run_medianblur, dst, src, ksize);

        CV_Error(cv::Error::StsBadArg, "unsupported combination of types");
    }

    static Border getBorder(const cv::GMatDesc& /* src */,
                                      int       /* ksize */)
    {
        int  borderType  = cv::BORDER_REPLICATE;
        auto borderValue = cv::Scalar();
        return { borderType, borderValue };
    }
};

GAPI_FLUID_KERNEL(GFluidRGB2YUV422, cv::gapi::imgproc::GRGB2YUV422, false)
{
    static const int Window = 1;
    static const auto Kind = cv::GFluidKernel::Kind::Filter;

    static void run(const cv::gapi::fluid::View& in,
                    cv::gapi::fluid::Buffer& out)
    {
        const auto *src = in.InLine<uchar>(0);
        auto *dst = out.OutLine<uchar>();

        run_rgb2yuv422_impl(dst, src, in.length());
    }
};

GAPI_FLUID_KERNEL(GFluidRGB2HSV, cv::gapi::imgproc::GRGB2HSV, true)
{
    static const int Window = 1;
    static const auto Kind = cv::GFluidKernel::Kind::Filter;

    static void run(const cv::gapi::fluid::View&   in,
                    cv::gapi::fluid::Buffer& out,
                    cv::gapi::fluid::Buffer& scratch)
    {
        const auto *src = in.InLine<uchar>(0);
        auto *dst = out.OutLine<uchar>();

        auto* sdiv_table = scratch.OutLine<int>(0);
        auto* hdiv_table = sdiv_table + 256;

        run_rgb2hsv_impl(dst, src, sdiv_table, hdiv_table, in.length());
    }

    static void initScratch(const cv::GMatDesc& /* in */,
                            cv::gapi::fluid::Buffer& scratch)
    {
        const int hsv_shift = 12;

        cv::GMatDesc desc;
        desc.chan  = 1;
        desc.depth = CV_32S;
        desc.size  = cv::Size(512, 1);

        cv::gapi::fluid::Buffer buffer(desc);
        scratch = std::move(buffer);

        auto* sdiv_table = scratch.OutLine<int>(0);
        auto* hdiv_table = sdiv_table + 256;

        sdiv_table[0] = hdiv_table[0] = 0;
        for(int i = 1; i < 256; i++ )
        {
            sdiv_table[i] = cv::saturate_cast<int>((255 << hsv_shift)/(1.*i));
            hdiv_table[i] = cv::saturate_cast<int>((180 << hsv_shift)/(6.*i));
        }

    }

    static void resetScratch(cv::gapi::fluid::Buffer& /* scratch */)
    {
    }
};

GAPI_FLUID_KERNEL(GFluidBayerGR2RGB, cv::gapi::imgproc::GBayerGR2RGB, false)
{
    static const int Window = 3;
    static const int LPI    = 2;

    static void run(const cv::gapi::fluid::View& in,
                    cv::gapi::fluid::Buffer& out)
    {
        const int height = in.meta().size.height;
        const int border_size = 1;
        const int width = in.length();

        constexpr int num_lines = LPI + 2 * border_size;
        const uchar* src[num_lines];
        uchar* dst[LPI];

        for (int i = 0; i < LPI; ++i)
        {
            dst[i] = out.OutLine<uchar>(i);
        }

        for (int i = 0; i < num_lines; ++i)
        {
            src[i] = in.InLine<uchar>(i - 1);
        }

        if (in.y() == -1)
        {
            run_bayergr2rgb_bg_impl(dst[1], src + border_size, width);
            std::copy_n(dst[1], width * 3, dst[0]);
        }
        else if (in.y() == height - LPI - 2 * border_size + 1)
        {
            run_bayergr2rgb_gr_impl(dst[0], src, width);
            std::copy_n(dst[0], width * 3, dst[1]);
        }
        else
        {
            run_bayergr2rgb_gr_impl(dst[0], src, width);
            run_bayergr2rgb_bg_impl(dst[1], src + border_size, width);
        }
    }

    static cv::gapi::fluid::Border getBorder(const cv::GMatDesc&)
    {
        int  borderType  = cv::BORDER_CONSTANT;
        auto borderValue = cv::Scalar();

        return { borderType, borderValue };
    }
};

template<typename T, typename Mapper, int chanNum>
struct LinearScratchDesc {
    using alpha_t = typename Mapper::alpha_type;
    using index_t = typename Mapper::index_type;

    alpha_t* alpha;
    alpha_t* clone;
    index_t* mapsx;
    alpha_t* beta;
    index_t* mapsy;
    T*       tmp;

    LinearScratchDesc(int /*inW*/, int /*inH*/, int outW, int outH,  void* data) {
        alpha = reinterpret_cast<alpha_t*>(data);
        clone = reinterpret_cast<alpha_t*>(alpha + outW);
        mapsx = reinterpret_cast<index_t*>(clone + outW*4);
        beta  = reinterpret_cast<alpha_t*>(mapsx + outW);
        mapsy = reinterpret_cast<index_t*>(beta  + outH);
        tmp   = reinterpret_cast<T*>      (mapsy + outH*2);
    }

    static int bufSize(int inW, int /*inH*/, int outW, int outH, int lpi) {
        auto size = outW * sizeof(alpha_t)     +
                    outW * sizeof(alpha_t) * 4 +  // alpha clones
                    outW * sizeof(index_t)     +
                    outH * sizeof(alpha_t)     +
                    outH * sizeof(index_t) * 2 +
                     inW * sizeof(T) * lpi * chanNum;

        return static_cast<int>(size);
    }
};
static inline double invRatio(int inSz, int outSz) {
    return static_cast<double>(outSz) / inSz;
}

static inline double ratio(int inSz, int outSz) {
    return 1 / invRatio(inSz, outSz);
}

template<typename T, typename Mapper, int chanNum = 1>
static inline void initScratchLinear(const cv::GMatDesc& in,
                                     const         Size& outSz,
                                     cv::gapi::fluid::Buffer& scratch,
                                     int  lpi) {
    using alpha_type = typename Mapper::alpha_type;
    static const auto unity = Mapper::unity;

    auto inSz = in.size;
    auto sbufsize = LinearScratchDesc<T, Mapper, chanNum>::bufSize(inSz.width, inSz.height, outSz.width, outSz.height, lpi);

    Size scratch_size{sbufsize, 1};

    cv::GMatDesc desc;
    desc.chan = 1;
    desc.depth = CV_8UC1;
    desc.size = scratch_size;

    cv::gapi::fluid::Buffer buffer(desc);
    scratch = std::move(buffer);

    double hRatio = ratio(in.size.width, outSz.width);
    double vRatio = ratio(in.size.height, outSz.height);

    LinearScratchDesc<T, Mapper, chanNum> scr(inSz.width, inSz.height, outSz.width, outSz.height, scratch.OutLineB());

    auto *alpha = scr.alpha;
    auto *clone = scr.clone;
    auto *index = scr.mapsx;

    for (int x = 0; x < outSz.width; x++) {
        auto map = Mapper::map(hRatio, 0, in.size.width, x);
        auto alpha0 = map.alpha0;
        auto index0 = map.index0;

        // TRICK:
        // Algorithm takes pair of input pixels, sx0'th and sx1'th,
        // and compute result as alpha0*src[sx0] + alpha1*src[sx1].
        // By definition: sx1 == sx0 + 1 either sx1 == sx0, and
        // alpha0 + alpha1 == unity (scaled appropriately).
        // Here we modify formulas for alpha0 and sx1: by assuming
        // that sx1 == sx0 + 1 always, and patching alpha0 so that
        // result remains intact.
        // Note that we need in.size.width >= 2, for both sx0 and
        // sx0+1 were indexing pixels inside the input's width.
        if (map.index1 != map.index0 + 1) {
            GAPI_DbgAssert(map.index1 == map.index0);
            GAPI_DbgAssert(in.size.width >= 2);
            if (map.index0 < in.size.width-1) {
                // sx1=sx0+1 fits inside row,
                // make sure alpha0=unity and alpha1=0,
                // so that result equals src[sx0]*unity
                alpha0 = saturate_cast<alpha_type>(unity);
            } else {
                // shift sx0 to left by 1 pixel,
                // and make sure that alpha0=0 and alpha1==1,
                // so that result equals to src[sx0+1]*unity
                alpha0 = 0;
                index0--;
            }
        }

        alpha[x] = alpha0;
        index[x] = index0;

        for (int l = 0; l < 4; l++) {
            clone[4*x + l] = alpha0;
        }
    }

    auto *beta    = scr.beta;
    auto *index_y = scr.mapsy;

    for (int y = 0; y < outSz.height; y++) {
        auto mapY = Mapper::map(vRatio, 0, in.size.height, y);
        beta[y] = mapY.alpha0;
        index_y[y] = mapY.index0;
        index_y[outSz.height + y] = mapY.index1;
    }
}

template<typename F, typename I>
struct MapperUnit {
    F alpha0, alpha1;
    I index0, index1;
};

inline static uint8_t calc(short alpha0, uint8_t src0, short alpha1, uint8_t src1) {
    constexpr static const int half = 1 << 14;
    return (src0 * alpha0 + src1 * alpha1 + half) >> 15;
}
struct Mapper {
    constexpr static const int ONE = 1 << 15;
    typedef short alpha_type;
    typedef short index_type;
    constexpr static const int unity = ONE;

    typedef MapperUnit<short, short> Unit;

    static inline Unit map(double ratio, int start, int max, int outCoord) {
        float f = static_cast<float>((outCoord + 0.5) * ratio - 0.5);
        int s = cvFloor(f);
        f -= s;

        Unit u;

        u.index0 = static_cast<short>(std::max(s - start, 0));
        u.index1 = static_cast<short>(((f == 0.0) || s + 1 >= max) ? s - start : s - start + 1);

        u.alpha0 = saturate_cast<short>(ONE * (1.0f - f));
        u.alpha1 = saturate_cast<short>(ONE * f);

        return u;
    }
};

template<typename T, class Mapper, int numChan>
static void calcRowLinearC(const cv::gapi::fluid::View  & in,
                           cv::gapi::fluid::Buffer& out,
                           cv::gapi::fluid::Buffer& scratch) {
    using alpha_type = typename Mapper::alpha_type;

    auto  inSz =  in.meta().size;
    auto outSz = out.meta().size;

    auto inY  = in.y();
    int outY = out.y();
    int lpi = out.lpi();

    GAPI_DbgAssert(outY + lpi <= outSz.height);
    GAPI_DbgAssert(lpi <= 4);

    LinearScratchDesc<T, Mapper, numChan> scr(inSz.width, inSz.height, outSz.width, outSz.height, scratch.OutLineB());

    const auto *alpha = scr.alpha;
    const auto *mapsx = scr.mapsx;
    const auto *beta_0 = scr.beta;
    const auto *mapsy = scr.mapsy;

    const auto *beta = beta_0 + outY;
    const T *src0[4];
    const T *src1[4];
    T* dst[4];

    for (int l = 0; l < lpi; l++) {
        auto index0 = mapsy[outY + l] - inY;
        auto index1 = mapsy[outSz.height + outY + l] - inY;
        src0[l] = in.InLine<const T>(index0);
        src1[l] = in.InLine<const T>(index1);
        dst[l] = out.OutLine<T>(l);
    }

#if CV_SSE4_1
    const auto* clone = scr.clone;
    auto* tmp = scr.tmp;

    if (inSz.width >= 16 && outSz.width >= 16)
    {
        sse41::calcRowLinear_8UC_Impl_<numChan>(reinterpret_cast<uint8_t**>(dst),
                                                reinterpret_cast<const uint8_t**>(src0),
                                                reinterpret_cast<const uint8_t**>(src1),
                                                reinterpret_cast<const short*>(alpha),
                                                reinterpret_cast<const short*>(clone),
                                                reinterpret_cast<const short*>(mapsx),
                                                reinterpret_cast<const short*>(beta),
                                                reinterpret_cast<uint8_t*>(tmp),
                                                inSz, outSz, lpi);

        return;
    }
#endif // CV_SSE4_1
    int length = out.length();
    for (int l = 0; l < lpi; l++) {
        constexpr static const auto unity = Mapper::unity;

        auto beta0 =                                   beta[l];
        auto beta1 = saturate_cast<alpha_type>(unity - beta[l]);

        for (int x = 0; x < length; x++) {
            auto alpha0 =                                   alpha[x];
            auto alpha1 = saturate_cast<alpha_type>(unity - alpha[x]);
            auto sx0 = mapsx[x];
            auto sx1 = sx0 + 1;

            for (int c = 0; c < numChan; c++) {
                auto idx0 = numChan*sx0 + c;
                auto idx1 = numChan*sx1 + c;
                T tmp0 = calc(beta0, src0[l][idx0], beta1, src1[l][idx0]);
                T tmp1 = calc(beta0, src0[l][idx1], beta1, src1[l][idx1]);
                dst[l][numChan * x + c] = calc(alpha0, tmp0, alpha1, tmp1);
            }
        }
    }
}

GAPI_FLUID_KERNEL(GFluidResize, cv::gapi::imgproc::GResize, true)
{
    static const int Window = 1;
    static const int LPI = 4;
    static const auto Kind = GFluidKernel::Kind::Resize;

    constexpr static const int INTER_RESIZE_COEF_BITS = 11;
    constexpr static const int INTER_RESIZE_COEF_SCALE = 1 << INTER_RESIZE_COEF_BITS;
    constexpr static const short ONE = INTER_RESIZE_COEF_SCALE;

   static void initScratch(const cv::GMatDesc& in,
                           cv::Size outSz, double fx, double fy, int /*interp*/,
                           cv::gapi::fluid::Buffer &scratch)
    {
       int outSz_w;
       int outSz_h;
       if (outSz.width == 0 || outSz.height == 0)
       {
           outSz_w = saturate_cast<int>(in.size.width * fx);
           outSz_h = saturate_cast<int>(in.size.height * fy);
       }
       else
       {
           outSz_w = outSz.width;
           outSz_h = outSz.height;
       }
       cv::Size outSize(outSz_w, outSz_h);

       if (in.chan == 3)
       {
           initScratchLinear<uchar, Mapper, 3>(in, outSize, scratch, LPI);
       }
       else if (in.chan == 4)
       {
           initScratchLinear<uchar, Mapper, 4>(in, outSize, scratch, LPI);
       }
    }

    static void resetScratch(cv::gapi::fluid::Buffer& /*scratch*/)
    {}

    static void run(const cv::gapi::fluid::View& in, cv::Size /*sz*/, double /*fx*/, double /*fy*/, int interp,
                    cv::gapi::fluid::Buffer& out,
                    cv::gapi::fluid::Buffer& scratch) {
        const int channels = in.meta().chan;
        GAPI_Assert((channels == 3 || channels == 4) && (interp == cv::INTER_LINEAR));

        if (channels == 3)
        {
            calcRowLinearC<uint8_t, Mapper, 3>(in, out, scratch);
        }
        else if (channels == 4)
        {
            calcRowLinearC<uint8_t, Mapper, 4>(in, out, scratch);
        }
    }
};

} // namespace fluid
} // namespace gapi
} // namespace cv

cv::GKernelPackage cv::gapi::imgproc::fluid::kernels()
{
    using namespace cv::gapi::fluid;

    return cv::gapi::kernels
    <   GFluidBGR2Gray
      , GFluidResize
      , GFluidRGB2Gray
      , GFluidRGB2GrayCustom
      , GFluidRGB2YUV
      , GFluidYUV2RGB
      , GFluidRGB2Lab
      , GFluidBGR2LUV
      , GFluidBlur
      , GFluidSepFilter
      , GFluidBoxFilter
      , GFluidFilter2D
      , GFluidErode
      , GFluidDilate
      , GFluidMedianBlur
      , GFluidGaussBlur
      , GFluidSobel
      , GFluidSobelXY
      , GFluidRGB2YUV422
      , GFluidRGB2HSV
      , GFluidBayerGR2RGB
    #if 0
      , GFluidCanny        -- not fluid (?)
      , GFluidEqualizeHist -- not fluid
    #endif
    >();
}

#endif // !defined(GAPI_STANDALONE)