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#include "opencv2/gpu/device/common.hpp"
#include "opencv2/gpu/device/vec_traits.hpp"
#include "opencv2/gpu/device/vec_math.hpp"
#include "opencv2/gpu/device/limits.hpp"

namespace cv { namespace gpu { namespace device
{
    namespace mog
    {
        ///////////////////////////////////////////////////////////////
        // Utility

        __device__ __forceinline__ float cvt(uchar val)
        {
            return val;
        }
        __device__ __forceinline__ float3 cvt(const uchar3& val)
        {
            return make_float3(val.x, val.y, val.z);
        }
        __device__ __forceinline__ float4 cvt(const uchar4& val)
        {
            return make_float4(val.x, val.y, val.z, val.w);
        }

        __device__ __forceinline__ float sqr(float val)
        {
            return val * val;
        }
        __device__ __forceinline__ float sqr(const float3& val)
        {
            return val.x * val.x + val.y * val.y + val.z * val.z;
        }
        __device__ __forceinline__ float sqr(const float4& val)
        {
            return val.x * val.x + val.y * val.y + val.z * val.z;
        }

        __device__ __forceinline__ float sum(float val)
        {
            return val;
        }
        __device__ __forceinline__ float sum(const float3& val)
        {
            return val.x + val.y + val.z;
        }
        __device__ __forceinline__ float sum(const float4& val)
        {
            return val.x + val.y + val.z;
        }

        __device__ __forceinline__ float clamp(float var, float learningRate, float diff, float minVar)
        {
             return ::fmaxf(var + learningRate * (diff * diff - var), minVar);
        }
        __device__ __forceinline__ float3 clamp(const float3& var, float learningRate, const float3& diff, float minVar)
        {
             return make_float3(::fmaxf(var.x + learningRate * (diff.x * diff.x - var.x), minVar),
                                ::fmaxf(var.y + learningRate * (diff.y * diff.y - var.y), minVar),
                                ::fmaxf(var.z + learningRate * (diff.z * diff.z - var.z), minVar));
        }
        __device__ __forceinline__ float4 clamp(const float4& var, float learningRate, const float4& diff, float minVar)
        {
             return make_float4(::fmaxf(var.x + learningRate * (diff.x * diff.x - var.x), minVar),
                                ::fmaxf(var.y + learningRate * (diff.y * diff.y - var.y), minVar),
                                ::fmaxf(var.z + learningRate * (diff.z * diff.z - var.z), minVar),
                                0.0f);
        }

        template <class Ptr2D>
        __device__ __forceinline__ void swap(Ptr2D& ptr, int x, int y, int k, int rows)
        {
            typename Ptr2D::elem_type val = ptr(k * rows + y, x);
            ptr(k * rows + y, x) = ptr((k + 1) * rows + y, x);
            ptr((k + 1) * rows + y, x) = val;
        }

        ///////////////////////////////////////////////////////////////
        // MOG without learning

        template <typename SrcT, typename WorkT>
        __global__ void mog_withoutLearning(const DevMem2D_<SrcT> frame, PtrStepb fgmask,
                                            const PtrStepf gmm_weight, const PtrStep_<WorkT> gmm_mean, const PtrStep_<WorkT> gmm_var,
                                            const int nmixtures, const float varThreshold, const float backgroundRatio)
        {
            const int x = blockIdx.x * blockDim.x + threadIdx.x;
            const int y = blockIdx.y * blockDim.y + threadIdx.y;

            if (x >= frame.cols || y >= frame.rows)
                return;

            WorkT pix = cvt(frame(y, x));

            int kHit = -1;
            int kForeground = -1;

            for (int k = 0; k < nmixtures; ++k)
            {
                if (gmm_weight(k * frame.rows + y, x) < numeric_limits<float>::epsilon())
                    break;

                WorkT mu = gmm_mean(k * frame.rows + y, x);
                WorkT var = gmm_var(k * frame.rows + y, x);

                WorkT diff = pix - mu;

                if (sqr(diff) < varThreshold * sum(var))
                {
                    kHit = k;
                    break;
                }
            }

            if (kHit >= 0)
            {
                float wsum = 0.0f;
                for (int k = 0; k < nmixtures; ++k)
                {
                    wsum += gmm_weight(k * frame.rows + y, x);

                    if (wsum > backgroundRatio)
                    {
                        kForeground = k + 1;
                        break;
                    }
                }
            }

            fgmask(y, x) = (uchar) (-(kHit < 0 || kHit >= kForeground));
        }

        template <typename SrcT, typename WorkT>
        void mog_withoutLearning_caller(DevMem2Db frame, DevMem2Db fgmask, DevMem2Df weight, DevMem2Db mean, DevMem2Db var,
                                        int nmixtures, float varThreshold, float backgroundRatio, cudaStream_t stream)
        {
            dim3 block(32, 8);
            dim3 grid(divUp(frame.cols, block.x), divUp(frame.rows, block.y));

            cudaSafeCall( cudaFuncSetCacheConfig(mog_withoutLearning<SrcT, WorkT>, cudaFuncCachePreferL1) );

            mog_withoutLearning<SrcT, WorkT><<<grid, block, 0, stream>>>((DevMem2D_<SrcT>) frame, fgmask,
                                                                         weight, (DevMem2D_<WorkT>) mean, (DevMem2D_<WorkT>) var,
                                                                         nmixtures, varThreshold, backgroundRatio);

            cudaSafeCall( cudaGetLastError() );

            if (stream == 0)
                cudaSafeCall( cudaDeviceSynchronize() );
        }

        ///////////////////////////////////////////////////////////////
        // MOG with learning

        template <typename SrcT, typename WorkT>
        __global__ void mog_withLearning(const DevMem2D_<SrcT> frame, PtrStepb fgmask,
                                         PtrStepf gmm_weight, PtrStepf gmm_sortKey, PtrStep_<WorkT> gmm_mean, PtrStep_<WorkT> gmm_var,
                                         const int nmixtures, const float varThreshold, const float backgroundRatio, const float learningRate, const float minVar)
        {
            const float w0 = 0.05f;
            const float sk0 = w0 / (30.0f * 0.5f * 2.0f);
            const float var0 = 30.0f * 0.5f * 30.0f * 0.5f * 4.0f;

            const int x = blockIdx.x * blockDim.x + threadIdx.x;
            const int y = blockIdx.y * blockDim.y + threadIdx.y;

            if (x >= frame.cols || y >= frame.rows)
                return;

            WorkT pix = cvt(frame(y, x));

            float wsum = 0.0f;
            int kHit = -1;
            int kForeground = -1;

            int k = 0;
            for (; k < nmixtures; ++k)
            {
                float w = gmm_weight(k * frame.rows + y, x);
                wsum += w;

                if (w < numeric_limits<float>::epsilon())
                    break;

                WorkT mu = gmm_mean(k * frame.rows + y, x);
                WorkT var = gmm_var(k * frame.rows + y, x);

                WorkT diff = pix - mu;

                if (sqr(diff) < varThreshold * sum(var))
                {
                    wsum -= w;
                    float dw = learningRate * (1.0f - w);

                    var = clamp(var, learningRate, diff, minVar);

                    float sortKey_prev = w / ::sqrtf(sum(var));
                    gmm_sortKey(k * frame.rows + y, x) = sortKey_prev;

                    float weight_prev = w + dw;
                    gmm_weight(k * frame.rows + y, x) = weight_prev;

                    WorkT mean_prev = mu + learningRate * diff;
                    gmm_mean(k * frame.rows + y, x) = mean_prev;

                    WorkT var_prev = var;
                    gmm_var(k * frame.rows + y, x) = var_prev;

                    int k1 = k - 1;

                    if (k1 >= 0)
                    {
                        float sortKey_next = gmm_sortKey(k1 * frame.rows + y, x);
                        float weight_next = gmm_weight(k1 * frame.rows + y, x);
                        WorkT mean_next = gmm_mean(k1 * frame.rows + y, x);
                        WorkT var_next = gmm_var(k1 * frame.rows + y, x);

                        for (; sortKey_next < sortKey_prev && k1 >= 0; --k1)
                        {
                            gmm_sortKey(k1 * frame.rows + y, x) = sortKey_prev;
                            gmm_sortKey((k1 + 1) * frame.rows + y, x) = sortKey_next;

                            gmm_weight(k1 * frame.rows + y, x) = weight_prev;
                            gmm_weight((k1 + 1) * frame.rows + y, x) = weight_next;

                            gmm_mean(k1 * frame.rows + y, x) = mean_prev;
                            gmm_mean((k1 + 1) * frame.rows + y, x) = mean_next;

                            gmm_var(k1 * frame.rows + y, x) = var_prev;
                            gmm_var((k1 + 1) * frame.rows + y, x) = var_next;

                            sortKey_prev = sortKey_next;
                            sortKey_next = k1 > 0 ? gmm_sortKey((k1 - 1) * frame.rows + y, x) : 0.0f;

                            weight_prev = weight_next;
                            weight_next = k1 > 0 ? gmm_weight((k1 - 1) * frame.rows + y, x) : 0.0f;

                            mean_prev = mean_next;
                            mean_next = k1 > 0 ? gmm_mean((k1 - 1) * frame.rows + y, x) : VecTraits<WorkT>::all(0.0f);

                            var_prev = var_next;
                            var_next = k1 > 0 ? gmm_var((k1 - 1) * frame.rows + y, x) : VecTraits<WorkT>::all(0.0f);
                        }
                    }

                    kHit = k1 + 1;
                    break;
                }
            }

            if (kHit < 0)
            {
                // no appropriate gaussian mixture found at all, remove the weakest mixture and create a new one
                kHit = k = ::min(k, nmixtures - 1);
                wsum += w0 - gmm_weight(k * frame.rows + y, x);

                gmm_weight(k * frame.rows + y, x) = w0;
                gmm_mean(k * frame.rows + y, x) = pix;
                gmm_var(k * frame.rows + y, x) = VecTraits<WorkT>::all(var0);
                gmm_sortKey(k * frame.rows + y, x) = sk0;
            }
            else
            {
                for( ; k < nmixtures; k++)
                    wsum += gmm_weight(k * frame.rows + y, x);
            }

            float wscale = 1.0f / wsum;
            wsum = 0;
            for (k = 0; k < nmixtures; ++k)
            {
                float w = gmm_weight(k * frame.rows + y, x);
                wsum += w *= wscale;

                gmm_weight(k * frame.rows + y, x) = w;
                gmm_sortKey(k * frame.rows + y, x) *= wscale;

                if (wsum > backgroundRatio && kForeground < 0)
                    kForeground = k + 1;
            }

            fgmask(y, x) = (uchar)(-(kHit >= kForeground));
        }

        template <typename SrcT, typename WorkT>
        void mog_withLearning_caller(DevMem2Db frame, DevMem2Db fgmask, DevMem2Df weight, DevMem2Df sortKey, DevMem2Db mean, DevMem2Db var,
                                     int nmixtures, float varThreshold, float backgroundRatio, float learningRate, float minVar,
                                     cudaStream_t stream)
        {
            dim3 block(32, 8);
            dim3 grid(divUp(frame.cols, block.x), divUp(frame.rows, block.y));

            cudaSafeCall( cudaFuncSetCacheConfig(mog_withLearning<SrcT, WorkT>, cudaFuncCachePreferL1) );

            mog_withLearning<SrcT, WorkT><<<grid, block, 0, stream>>>((DevMem2D_<SrcT>) frame, fgmask,
                                                                      weight, sortKey, (DevMem2D_<WorkT>) mean, (DevMem2D_<WorkT>) var,
                                                                      nmixtures, varThreshold, backgroundRatio, learningRate, minVar);

            cudaSafeCall( cudaGetLastError() );

            if (stream == 0)
                cudaSafeCall( cudaDeviceSynchronize() );
        }

        ///////////////////////////////////////////////////////////////
        // MOG

        void mog_gpu(DevMem2Db frame, int cn, DevMem2Db fgmask, DevMem2Df weight, DevMem2Df sortKey, DevMem2Db mean, DevMem2Db var, int nmixtures, float varThreshold, float learningRate, float backgroundRatio, float noiseSigma, cudaStream_t stream)
        {
            typedef void (*withoutLearning_t)(DevMem2Db frame, DevMem2Db fgmask, DevMem2Df weight, DevMem2Db mean, DevMem2Db var, int nmixtures, float varThreshold, float backgroundRatio, cudaStream_t stream);
            typedef void (*withLearning_t)(DevMem2Db frame, DevMem2Db fgmask, DevMem2Df weight, DevMem2Df sortKey, DevMem2Db mean, DevMem2Db var, int nmixtures, float varThreshold, float backgroundRatio, float learningRate, float minVar, cudaStream_t stream);

            static const withoutLearning_t withoutLearning[] =
            {
                0, mog_withoutLearning_caller<uchar, float>, 0, mog_withoutLearning_caller<uchar3, float3>, mog_withoutLearning_caller<uchar4, float4>
            };
            static const withLearning_t withLearning[] =
            {
                0, mog_withLearning_caller<uchar, float>, 0, mog_withLearning_caller<uchar3, float3>, mog_withLearning_caller<uchar4, float4>
            };

            const float minVar = noiseSigma * noiseSigma;

            if (learningRate > 0.0f)
                withLearning[cn](frame, fgmask, weight, sortKey, mean, var, nmixtures, varThreshold, backgroundRatio, learningRate, minVar, stream);
            else
                withoutLearning[cn](frame, fgmask, weight, mean, var, nmixtures, varThreshold, backgroundRatio, stream);
        }

        template <typename WorkT, typename OutT>
        __global__ void getBackgroundImage(const PtrStepf gmm_weight, const PtrStep_<WorkT> gmm_mean, DevMem2D_<OutT> dst, const int nmixtures, const float backgroundRatio)
        {
            const int x = blockIdx.x * blockDim.x + threadIdx.x;
            const int y = blockIdx.y * blockDim.y + threadIdx.y;

            if (x >= dst.cols || y >= dst.rows)
                return;

            WorkT meanVal = VecTraits<WorkT>::all(0.0f);
            float totalWeight = 0.0f;

            for (int mode = 0; mode < nmixtures; ++mode)
            {
                float weight = gmm_weight(mode * dst.rows + y, x);

                WorkT mean = gmm_mean(mode * dst.rows + y, x);
                meanVal = meanVal + weight * mean;

                totalWeight += weight;

                if(totalWeight > backgroundRatio)
                    break;
            }

            meanVal = meanVal * (1.f / totalWeight);

            dst(y, x) = saturate_cast<OutT>(meanVal);
        }

        template <typename WorkT, typename OutT>
        void getBackgroundImage_caller(DevMem2Df weight, DevMem2Db mean, DevMem2Db dst, int nmixtures, float backgroundRatio, cudaStream_t stream)
        {
            dim3 block(32, 8);
            dim3 grid(divUp(dst.cols, block.x), divUp(dst.rows, block.y));

            cudaSafeCall( cudaFuncSetCacheConfig(getBackgroundImage<WorkT, OutT>, cudaFuncCachePreferL1) );

            getBackgroundImage<WorkT, OutT><<<grid, block, 0, stream>>>(weight, (DevMem2D_<WorkT>) mean, (DevMem2D_<OutT>) dst, nmixtures, backgroundRatio);
            cudaSafeCall( cudaGetLastError() );

            if (stream == 0)
                cudaSafeCall( cudaDeviceSynchronize() );
        }

        void getBackgroundImage_gpu(int cn, DevMem2Df weight, DevMem2Db mean, DevMem2Db dst, int nmixtures, float backgroundRatio, cudaStream_t stream)
        {
            typedef void (*func_t)(DevMem2Df weight, DevMem2Db mean, DevMem2Db dst, int nmixtures, float backgroundRatio, cudaStream_t stream);

            static const func_t funcs[] =
            {
                0, getBackgroundImage_caller<float, uchar>, 0, getBackgroundImage_caller<float3, uchar3>, getBackgroundImage_caller<float4, uchar4>
            };

            funcs[cn](weight, mean, dst, nmixtures, backgroundRatio, stream);
        }

        ///////////////////////////////////////////////////////////////
        // MOG2

        __constant__ int           c_nmixtures;
        __constant__ float         c_Tb;
        __constant__ float         c_TB;
        __constant__ float         c_Tg;
        __constant__ float         c_varInit;
        __constant__ float         c_varMin;
        __constant__ float         c_varMax;
        __constant__ float         c_tau;
        __constant__ unsigned char c_shadowVal;

        void loadConstants(int nmixtures, float Tb, float TB, float Tg, float varInit, float varMin, float varMax, float tau, unsigned char shadowVal)
        {
            varMin = ::fminf(varMin, varMax);
            varMax = ::fmaxf(varMin, varMax);

            cudaSafeCall( cudaMemcpyToSymbol(c_nmixtures, &nmixtures, sizeof(int)) );
            cudaSafeCall( cudaMemcpyToSymbol(c_Tb, &Tb, sizeof(float)) );
            cudaSafeCall( cudaMemcpyToSymbol(c_TB, &TB, sizeof(float)) );
            cudaSafeCall( cudaMemcpyToSymbol(c_Tg, &Tg, sizeof(float)) );
            cudaSafeCall( cudaMemcpyToSymbol(c_varInit, &varInit, sizeof(float)) );
            cudaSafeCall( cudaMemcpyToSymbol(c_varMin, &varMin, sizeof(float)) );
            cudaSafeCall( cudaMemcpyToSymbol(c_varMax, &varMax, sizeof(float)) );
            cudaSafeCall( cudaMemcpyToSymbol(c_tau, &tau, sizeof(float)) );
            cudaSafeCall( cudaMemcpyToSymbol(c_shadowVal, &shadowVal, sizeof(unsigned char)) );
        }

        template <bool detectShadows, typename SrcT, typename WorkT>
        __global__ void mog2(const DevMem2D_<SrcT> frame, PtrStepb fgmask, PtrStepb modesUsed,
                             PtrStepf gmm_weight, PtrStepf gmm_variance, PtrStep_<WorkT> gmm_mean,
                             const float alphaT, const float alpha1, const float prune)
        {
            const int x = blockIdx.x * blockDim.x + threadIdx.x;
            const int y = blockIdx.y * blockDim.y + threadIdx.y;

            if (x >= frame.cols || y >= frame.rows)
                return;

            WorkT pix = cvt(frame(y, x));

            //calculate distances to the modes (+ sort)
            //here we need to go in descending order!!!

            bool background = false; // true - the pixel classified as background

            //internal:

            bool fitsPDF = false; //if it remains zero a new GMM mode will be added

            int nmodes = modesUsed(y, x);
            int nNewModes = nmodes; //current number of modes in GMM

            float totalWeight = 0.0f;

            //go through all modes

            for (int mode = 0; mode < nmodes; ++mode)
            {
                //need only weight if fit is found
                float weight = alpha1 * gmm_weight(mode * frame.rows + y, x) + prune;

                //fit not found yet
                if (!fitsPDF)
                {
                    //check if it belongs to some of the remaining modes
                    float var = gmm_variance(mode * frame.rows + y, x);

                    WorkT mean = gmm_mean(mode * frame.rows + y, x);

                    //calculate difference and distance
                    WorkT diff = mean - pix;
                    float dist2 = sqr(diff);

                    //background? - Tb - usually larger than Tg
                    if (totalWeight < c_TB && dist2 < c_Tb * var)
                        background = true;

                    //check fit
                    if (dist2 < c_Tg * var)
                    {
                        //belongs to the mode
                        fitsPDF = true;

                        //update distribution

                        //update weight
                        weight += alphaT;
                        float k = alphaT / weight;

                        //update mean
                        gmm_mean(mode * frame.rows + y, x) = mean - k * diff;

                        //update variance
                        float varnew = var + k * (dist2 - var);

                        //limit the variance
                        varnew = ::fmaxf(varnew, c_varMin);
                        varnew = ::fminf(varnew, c_varMax);

                        gmm_variance(mode * frame.rows + y, x) = varnew;

                        //sort
                        //all other weights are at the same place and
                        //only the matched (iModes) is higher -> just find the new place for it

                        for (int i = mode; i > 0; --i)
                        {
                            //check one up
                            if (weight < gmm_weight((i - 1) * frame.rows + y, x))
                                break;

                            //swap one up
                            swap(gmm_weight, x, y, i - 1, frame.rows);
                            swap(gmm_variance, x, y, i - 1, frame.rows);
                            swap(gmm_mean, x, y, i - 1, frame.rows);
                        }

                        //belongs to the mode - bFitsPDF becomes 1
                    }
                } // !fitsPDF

                //check prune
                if (weight < -prune)
                {
                    weight = 0.0;
                    nmodes--;
                }

                gmm_weight(mode * frame.rows + y, x) = weight; //update weight by the calculated value
                totalWeight += weight;
            }

            //renormalize weights

            totalWeight = 1.f / totalWeight;
            for (int mode = 0; mode < nmodes; ++mode)
                gmm_weight(mode * frame.rows + y, x) *= totalWeight;

            nmodes = nNewModes;

            //make new mode if needed and exit

            if (!fitsPDF)
            {
                // replace the weakest or add a new one
                int mode = nmodes == c_nmixtures ? c_nmixtures - 1 : nmodes++;

                if (nmodes == 1)
                    gmm_weight(mode * frame.rows + y, x) = 1.f;
                else
                {
                    gmm_weight(mode * frame.rows + y, x) = alphaT;

                    // renormalize all other weights

                    for (int i = 0; i < nmodes - 1; ++i)
                        gmm_weight(i * frame.rows + y, x) *= alpha1;
                }

                // init

                gmm_mean(mode * frame.rows + y, x) = pix;
                gmm_variance(mode * frame.rows + y, x) = c_varInit;

                //sort
                //find the new place for it

                for (int i = nmodes - 1; i > 0; --i)
                {
                    // check one up
                    if (alphaT < gmm_weight((i - 1) * frame.rows + y, x))
                        break;

                    //swap one up
                    swap(gmm_weight, x, y, i - 1, frame.rows);
                    swap(gmm_variance, x, y, i - 1, frame.rows);
                    swap(gmm_mean, x, y, i - 1, frame.rows);
                }
            }

            //set the number of modes
            modesUsed(y, x) = nmodes;

            bool isShadow = false;
            if (detectShadows && !background)
            {
                float tWeight = 0.0f;

                // check all the components  marked as background:
                for (int mode = 0; mode < nmodes; ++mode)
                {
                    WorkT mean = gmm_mean(mode * frame.rows + y, x);

                    WorkT pix_mean = pix * mean;

                    float numerator = sum(pix_mean);
                    float denominator = sqr(mean);

                    // no division by zero allowed
                    if (denominator == 0)
                        break;

                    // if tau < a < 1 then also check the color distortion
                    if (numerator <= denominator && numerator >= c_tau * denominator)
                    {
                        float a = numerator / denominator;

                        WorkT dD = a * mean - pix;

                        if (sqr(dD) < c_Tb * gmm_variance(mode * frame.rows + y, x) * a * a)
                        {
                            isShadow = true;
                            break;
                        }
                    };

                    tWeight += gmm_weight(mode * frame.rows + y, x);
                    if (tWeight > c_TB)
                        break;
                };
            }

            fgmask(y, x) = background ? 0 : isShadow ? c_shadowVal : 255;
        }

        template <typename SrcT, typename WorkT>
        void mog2_caller(DevMem2Db frame, DevMem2Db fgmask, DevMem2Db modesUsed, DevMem2Df weight, DevMem2Df variance, DevMem2Db mean,
                         float alphaT, float prune, bool detectShadows, cudaStream_t stream)
        {
            dim3 block(32, 8);
            dim3 grid(divUp(frame.cols, block.x), divUp(frame.rows, block.y));

            const float alpha1 = 1.0f - alphaT;

            if (detectShadows)
            {
                cudaSafeCall( cudaFuncSetCacheConfig(mog2<true, SrcT, WorkT>, cudaFuncCachePreferL1) );

                mog2<true, SrcT, WorkT><<<grid, block, 0, stream>>>((DevMem2D_<SrcT>) frame, fgmask, modesUsed,
                                                                    weight, variance, (DevMem2D_<WorkT>) mean,
                                                                    alphaT, alpha1, prune);
            }
            else
            {
                cudaSafeCall( cudaFuncSetCacheConfig(mog2<false, SrcT, WorkT>, cudaFuncCachePreferL1) );

                mog2<false, SrcT, WorkT><<<grid, block, 0, stream>>>((DevMem2D_<SrcT>) frame, fgmask, modesUsed,
                                                                    weight, variance, (DevMem2D_<WorkT>) mean,
                                                                    alphaT, alpha1, prune);
            }

            cudaSafeCall( cudaGetLastError() );

            if (stream == 0)
                cudaSafeCall( cudaDeviceSynchronize() );
        }

        void mog2_gpu(DevMem2Db frame, int cn, DevMem2Db fgmask, DevMem2Db modesUsed, DevMem2Df weight, DevMem2Df variance, DevMem2Db mean,
                      float alphaT, float prune, bool detectShadows, cudaStream_t stream)
        {
            typedef void (*func_t)(DevMem2Db frame, DevMem2Db fgmask, DevMem2Db modesUsed, DevMem2Df weight, DevMem2Df variance, DevMem2Db mean, float alphaT, float prune, bool detectShadows, cudaStream_t stream);

            static const func_t funcs[] =
            {
                0, mog2_caller<uchar, float>, 0, mog2_caller<uchar3, float3>, mog2_caller<uchar4, float4>
            };

            funcs[cn](frame, fgmask, modesUsed, weight, variance, mean, alphaT, prune, detectShadows, stream);
        }

        template <typename WorkT, typename OutT>
        __global__ void getBackgroundImage2(const DevMem2Db modesUsed, const PtrStepf gmm_weight, const PtrStep_<WorkT> gmm_mean, PtrStep_<OutT> dst)
        {
            const int x = blockIdx.x * blockDim.x + threadIdx.x;
            const int y = blockIdx.y * blockDim.y + threadIdx.y;

            if (x >= modesUsed.cols || y >= modesUsed.rows)
                return;

            int nmodes = modesUsed(y, x);

            WorkT meanVal = VecTraits<WorkT>::all(0.0f);
            float totalWeight = 0.0f;

            for (int mode = 0; mode < nmodes; ++mode)
            {
                float weight = gmm_weight(mode * modesUsed.rows + y, x);

                WorkT mean = gmm_mean(mode * modesUsed.rows + y, x);
                meanVal = meanVal + weight * mean;

                totalWeight += weight;

                if(totalWeight > c_TB)
                    break;
            }

            meanVal = meanVal * (1.f / totalWeight);

            dst(y, x) = saturate_cast<OutT>(meanVal);
        }

        template <typename WorkT, typename OutT>
        void getBackgroundImage2_caller(DevMem2Db modesUsed, DevMem2Df weight, DevMem2Db mean, DevMem2Db dst, cudaStream_t stream)
        {
            dim3 block(32, 8);
            dim3 grid(divUp(modesUsed.cols, block.x), divUp(modesUsed.rows, block.y));

            cudaSafeCall( cudaFuncSetCacheConfig(getBackgroundImage2<WorkT, OutT>, cudaFuncCachePreferL1) );

            getBackgroundImage2<WorkT, OutT><<<grid, block, 0, stream>>>(modesUsed, weight, (DevMem2D_<WorkT>) mean, (DevMem2D_<OutT>) dst);
            cudaSafeCall( cudaGetLastError() );

            if (stream == 0)
                cudaSafeCall( cudaDeviceSynchronize() );
        }

        void getBackgroundImage2_gpu(int cn, DevMem2Db modesUsed, DevMem2Df weight, DevMem2Db mean, DevMem2Db dst, cudaStream_t stream)
        {
            typedef void (*func_t)(DevMem2Db modesUsed, DevMem2Df weight, DevMem2Db mean, DevMem2Db dst, cudaStream_t stream);

            static const func_t funcs[] =
            {
                0, getBackgroundImage2_caller<float, uchar>, 0, getBackgroundImage2_caller<float3, uchar3>, getBackgroundImage2_caller<float4, uchar4>
            };

            funcs[cn](modesUsed, weight, mean, dst, stream);
        }
    }
}}}
