resize

#ifndef FBC_CV_RESIZE_HPP_
#define FBC_CV_RESIZE_HPP_

/* reference: imgproc/include/opencv2/imgproc.hpp
              imgproc/src/imgwarp.cpp
*/

#include "core/mat.hpp"
#include "core/base.hpp"
#include "core/saturate.hpp"
#include "core/utility.hpp"
#include "imgproc.hpp"

namespace fbc {

static const int MAX_ESIZE = 16;

// interpolation formulas and tables
const int INTER_RESIZE_COEF_BITS = 11;
const int INTER_RESIZE_COEF_SCALE = 1 << INTER_RESIZE_COEF_BITS;

template<typename _Tp, int chs> static int resize_nearest(const Mat_<_Tp, chs>& src, Mat_<_Tp, chs>& dst);
template<typename _Tp, int chs> static int resize_linear(const Mat_<_Tp, chs>& src, Mat_<_Tp, chs>& dst);
template<typename _Tp, int chs> static int resize_cubic(const Mat_<_Tp, chs>& src, Mat_<_Tp, chs>& dst);
template<typename _Tp, int chs> static int resize_area(const Mat_<_Tp, chs>& src, Mat_<_Tp, chs>& dst);
template<typename _Tp, int chs> static int resize_lanczos4(const Mat_<_Tp, chs>& src, Mat_<_Tp, chs>& dst);

// resize the image src down to or up to the specified size
// support type: uchar/float
template<typename _Tp, int chs>
int resize(const Mat_<_Tp, chs>& src, Mat_<_Tp, chs>& dst, int interpolation = NTER_LINEAR)
{
    FBC_Assert((interpolation >= 0) && (interpolation < 5));
    FBC_Assert((src.rows >= 4 && src.cols >= 4) && (dst.rows >= 4  && dst.cols >= 4));
    FBC_Assert((sizeof(_Tp) == 1) || sizeof(_Tp) == 4); // uchar || float

    Size ssize = src.size();
    Size dsize = dst.size();

    if (dsize == ssize) {
        // Source and destination are of same size. Use simple copy.
        src.copyTo(dst);
        return 0;
    }

    switch (interpolation) {
        case 0: {
            resize_nearest(src, dst);
            break;
        }
        case 1: {
            resize_linear(src, dst);
            break;
        }
        case 2: {
            resize_cubic(src, dst);
            break;
        }
        case 3: {
            resize_area(src, dst);
            break;
        }
        case 4: {
            resize_lanczos4(src, dst);
            break;
        }
        default:
            return -1;
    }

    return 0;
}

struct DecimateAlpha
{
    int si, di;
    float alpha;
};

template<typename type>
static int computeResizeAreaTab(int ssize, int dsize, int cn, double scale, DecimateAlpha* tab)
{
    int k = 0;
    for (int dx = 0; dx < dsize; dx++) {
        double fsx1 = dx * scale;
        double fsx2 = fsx1 + scale;
        double cellWidth = std::min(scale, ssize - fsx1);

        int sx1 = fbcCeil(fsx1), sx2 = fbcFloor(fsx2);

        sx2 = std::min(sx2, ssize - 1);
        sx1 = std::min(sx1, sx2);

        if (sx1 - fsx1 > 1e-3) {
            assert(k < ssize * 2);
            tab[k].di = dx * cn;
            tab[k].si = (sx1 - 1) * cn;
            tab[k++].alpha = (float)((sx1 - fsx1) / cellWidth);
        }

        for (int sx = sx1; sx < sx2; sx++) {
            assert(k < ssize * 2);
            tab[k].di = dx * cn;
            tab[k].si = sx * cn;
            tab[k++].alpha = float(1.0 / cellWidth);
        }

        if (fsx2 - sx2 > 1e-3) {
            assert(k < ssize * 2);
            tab[k].di = dx * cn;
            tab[k].si = sx2 * cn;
            tab[k++].alpha = (float)(std::min(std::min(fsx2 - sx2, 1.), cellWidth) / cellWidth);
        }
    }
    return k;
}

template<typename ST, typename DT> struct Cast
{
    typedef ST type1;
    typedef DT rtype;

    DT operator()(ST val) const { return saturate_cast<DT>(val); }
};

template<typename ST, typename DT, int bits> struct FixedPtCast
{
    typedef ST type1;
    typedef DT rtype;
    enum { SHIFT = bits, DELTA = 1 << (bits - 1) };

    DT operator()(ST val) const { return saturate_cast<DT>((val + DELTA) >> SHIFT); }
};

template<typename type>
static type clip(type x, type a, type b)
{
    return x >= a ? (x < b ? x : b - 1) : a;
}

template<typename T, typename WT, typename AT>
struct HResizeLinear
{
    typedef T value_type;
    typedef WT buf_type;
    typedef AT alpha_type;

    void operator()(const T** src, WT** dst, int count,
        const int* xofs, const AT* alpha,
        int swidth, int dwidth, int cn, int xmin, int xmax, int ONE) const
    {
        int dx, k;
        int dx0 = 0;

        for (k = 0; k <= count - 2; k++) {
            const T *S0 = src[k], *S1 = src[k + 1];
            WT *D0 = dst[k], *D1 = dst[k + 1];
            for (dx = dx0; dx < xmax; dx++) {
                int sx = xofs[dx];
                WT a0 = alpha[dx * 2], a1 = alpha[dx * 2 + 1];
                WT t0 = S0[sx] * a0 + S0[sx + cn] * a1;
                WT t1 = S1[sx] * a0 + S1[sx + cn] * a1;
                D0[dx] = t0; D1[dx] = t1;
            }

            for (; dx < dwidth; dx++) {
                int sx = xofs[dx];
                D0[dx] = WT(S0[sx] * ONE); D1[dx] = WT(S1[sx] * ONE);
            }
        }

        for (; k < count; k++) {
            const T *S = src[k];
            WT *D = dst[k];
            for (dx = 0; dx < xmax; dx++) {
                int sx = xofs[dx];
                D[dx] = S[sx] * alpha[dx * 2] + S[sx + cn] * alpha[dx * 2 + 1];
            }

            for (; dx < dwidth; dx++) {
                D[dx] = WT(S[xofs[dx]] * ONE);
            }
        }
    }
};

template<typename T, typename WT, typename AT, class CastOp>
struct VResizeLinear
{
    typedef T value_type;
    typedef WT buf_type;
    typedef AT alpha_type;

    void operator()(const WT** src, T* dst, const AT* beta, int width) const
    {
        WT b0 = beta[0], b1 = beta[1];
        const WT *S0 = src[0], *S1 = src[1];
        CastOp castOp;
        int x = 0;

        for (; x <= width - 4; x += 4) {
            WT t0, t1;
            t0 = S0[x] * b0 + S1[x] * b1;
            t1 = S0[x + 1] * b0 + S1[x + 1] * b1;
            dst[x] = castOp(t0); dst[x + 1] = castOp(t1);
            t0 = S0[x + 2] * b0 + S1[x + 2] * b1;
            t1 = S0[x + 3] * b0 + S1[x + 3] * b1;
            dst[x + 2] = castOp(t0); dst[x + 3] = castOp(t1);
        }

        for (; x < width; x++) {
            dst[x] = castOp(S0[x] * b0 + S1[x] * b1);
        }
    }
};

template<>
struct VResizeLinear<uchar, int, short, FixedPtCast<int, uchar, INTER_RESIZE_COEF_BITS * 2>>
{
    typedef uchar value_type;
    typedef int buf_type;
    typedef short alpha_type;

    void operator()(const buf_type** src, value_type* dst, const alpha_type* beta, int width) const
    {
        alpha_type b0 = beta[0], b1 = beta[1];
        const buf_type *S0 = src[0], *S1 = src[1];
        int x = 0;

        for (; x <= width - 4; x += 4) {
            dst[x + 0] = uchar((((b0 * (S0[x + 0] >> 4)) >> 16) + ((b1 * (S1[x + 0] >> 4)) >> 16) + 2) >> 2);
            dst[x + 1] = uchar((((b0 * (S0[x + 1] >> 4)) >> 16) + ((b1 * (S1[x + 1] >> 4)) >> 16) + 2) >> 2);
            dst[x + 2] = uchar((((b0 * (S0[x + 2] >> 4)) >> 16) + ((b1 * (S1[x + 2] >> 4)) >> 16) + 2) >> 2);
            dst[x + 3] = uchar((((b0 * (S0[x + 3] >> 4)) >> 16) + ((b1 * (S1[x + 3] >> 4)) >> 16) + 2) >> 2);
        }

        for (; x < width; x++) {
            dst[x] = uchar((((b0 * (S0[x] >> 4)) >> 16) + ((b1 * (S1[x] >> 4)) >> 16) + 2) >> 2);
        }
    }
};

template<typename T, typename WT, typename AT>
struct HResizeCubic
{
    typedef T value_type;
    typedef WT buf_type;
    typedef AT alpha_type;

    void operator()(const T** src, WT** dst, int count,
        const int* xofs, const AT* alpha,
        int swidth, int dwidth, int cn, int xmin, int xmax) const
    {
        for (int k = 0; k < count; k++) {
            const T *S = src[k];
            WT *D = dst[k];
            int dx = 0, limit = xmin;
            for (;;) {
                for (; dx < limit; dx++, alpha += 4) {
                    int j, sx = xofs[dx] - cn;
                    WT v = 0;
                    for (j = 0; j < 4; j++) {
                        int sxj = sx + j*cn;
                        if ((unsigned)sxj >= (unsigned)swidth) {
                            while (sxj < 0)
                                sxj += cn;
                            while (sxj >= swidth)
                                sxj -= cn;
                        }
                        v += S[sxj] * alpha[j];
                    }
                    D[dx] = v;
                }
                if (limit == dwidth)
                    break;
                for (; dx < xmax; dx++, alpha += 4) {
                    int sx = xofs[dx];
                    D[dx] = S[sx - cn] * alpha[0] + S[sx] * alpha[1] +
                        S[sx + cn] * alpha[2] + S[sx + cn * 2] * alpha[3];
                }
                limit = dwidth;
            }
            alpha -= dwidth * 4;
        }
    }
};

template<typename T, typename WT, typename AT, class CastOp>
struct VResizeCubic
{
    typedef T value_type;
    typedef WT buf_type;
    typedef AT alpha_type;

    void operator()(const WT** src, T* dst, const AT* beta, int width) const
    {
        WT b0 = beta[0], b1 = beta[1], b2 = beta[2], b3 = beta[3];
        const WT *S0 = src[0], *S1 = src[1], *S2 = src[2], *S3 = src[3];
        CastOp castOp;

        int x = 0;
        for (; x < width; x++) {
            dst[x] = castOp(S0[x] * b0 + S1[x] * b1 + S2[x] * b2 + S3[x] * b3);
        }
    }
};

template<typename T, typename WT, typename AT>
struct HResizeLanczos4
{
    typedef T value_type;
    typedef WT buf_type;
    typedef AT alpha_type;

    void operator()(const T** src, WT** dst, int count,
        const int* xofs, const AT* alpha,
        int swidth, int dwidth, int cn, int xmin, int xmax) const
    {
        for (int k = 0; k < count; k++) {
            const T *S = src[k];
            WT *D = dst[k];
            int dx = 0, limit = xmin;
            for (;;) {
                for (; dx < limit; dx++, alpha += 8) {
                    int j, sx = xofs[dx] - cn * 3;
                    WT v = 0;
                    for (j = 0; j < 8; j++) {
                        int sxj = sx + j*cn;
                        if ((unsigned)sxj >= (unsigned)swidth) {
                            while (sxj < 0)
                                sxj += cn;
                            while (sxj >= swidth)
                                sxj -= cn;
                        }
                        v += S[sxj] * alpha[j];
                    }
                    D[dx] = v;
                }
                if (limit == dwidth)
                    break;
                for (; dx < xmax; dx++, alpha += 8) {
                    int sx = xofs[dx];
                    D[dx] = S[sx - cn * 3] * alpha[0] + S[sx - cn * 2] * alpha[1] +
                        S[sx - cn] * alpha[2] + S[sx] * alpha[3] +
                        S[sx + cn] * alpha[4] + S[sx + cn * 2] * alpha[5] +
                        S[sx + cn * 3] * alpha[6] + S[sx + cn * 4] * alpha[7];
                }
                limit = dwidth;
            }
            alpha -= dwidth * 8;
        }
    }
};

template<typename T, typename WT, typename AT, class CastOp>
struct VResizeLanczos4
{
    typedef T value_type;
    typedef WT buf_type;
    typedef AT alpha_type;

    void operator()(const WT** src, T* dst, const AT* beta, int width) const
    {
        CastOp castOp;
        int k, x = 0;

        for (; x <= width - 4; x += 4) {
            WT b = beta[0];
            const WT* S = src[0];
            WT s0 = S[x] * b, s1 = S[x + 1] * b, s2 = S[x + 2] * b, s3 = S[x + 3] * b;

            for (k = 1; k < 8; k++) {
                b = beta[k]; S = src[k];
                s0 += S[x] * b; s1 += S[x + 1] * b;
                s2 += S[x + 2] * b; s3 += S[x + 3] * b;
            }

            dst[x] = castOp(s0); dst[x + 1] = castOp(s1);
            dst[x + 2] = castOp(s2); dst[x + 3] = castOp(s3);
        }

        for (; x < width; x++) {
            dst[x] = castOp(src[0][x] * beta[0] + src[1][x] * beta[1] +
                src[2][x] * beta[2] + src[3][x] * beta[3] + src[4][x] * beta[4] +
                src[5][x] * beta[5] + src[6][x] * beta[6] + src[7][x] * beta[7]);
        }
    }
};

template<typename T>
struct ResizeAreaFastVec
{
    ResizeAreaFastVec(int _scale_x, int _scale_y, int _cn, int _step) :
        scale_x(_scale_x), scale_y(_scale_y), cn(_cn), step(_step)
    {
        fast_mode = scale_x == 2 && scale_y == 2 && (cn == 1 || cn == 3 || cn == 4);
    }

    int operator() (const T* S, T* D, int w) const
    {
        if (!fast_mode) {
            return 0;
        }

        const T* nextS = (const T*)((const uchar*)S + step);
        int dx = 0;

        if (cn == 1) {
            for (; dx < w; ++dx) {
                int index = dx * 2;
                D[dx] = (T)((S[index] + S[index + 1] + nextS[index] + nextS[index + 1] + 2) >> 2);
            }
        }
        else if (cn == 3) {
            for (; dx < w; dx += 3) {
                int index = dx * 2;
                D[dx] = (T)((S[index] + S[index + 3] + nextS[index] + nextS[index + 3] + 2) >> 2);
                D[dx + 1] = (T)((S[index + 1] + S[index + 4] + nextS[index + 1] + nextS[index + 4] + 2) >> 2);
                D[dx + 2] = (T)((S[index + 2] + S[index + 5] + nextS[index + 2] + nextS[index + 5] + 2) >> 2);
            }
        } else {
            FBC_Assert(cn == 4);
            for (; dx < w; dx += 4) {
                int index = dx * 2;
                D[dx] = (T)((S[index] + S[index + 4] + nextS[index] + nextS[index + 4] + 2) >> 2);
                D[dx + 1] = (T)((S[index + 1] + S[index + 5] + nextS[index + 1] + nextS[index + 5] + 2) >> 2);
                D[dx + 2] = (T)((S[index + 2] + S[index + 6] + nextS[index + 2] + nextS[index + 6] + 2) >> 2);
                D[dx + 3] = (T)((S[index + 3] + S[index + 7] + nextS[index + 3] + nextS[index + 7] + 2) >> 2);
            }
        }

        return dx;
    }

private:
    int scale_x, scale_y;
    int cn;
    bool fast_mode;
    int step;
};

template<typename _Tp, typename value_type, typename buf_type, typename alpha_type, int chs>
static void resizeGeneric_Linear(const Mat_<_Tp, chs>& src, Mat_<_Tp, chs>& dst,
    const int* xofs, const void* _alpha, const int* yofs, const void* _beta, int xmin, int xmax, int ksize, int ONE)
{
    Size ssize = src.size(), dsize = dst.size();
    int dy, cn = src.channels;
    ssize.width *= cn;
    dsize.width *= cn;
    xmin *= cn;
    xmax *= cn;
    // image resize is a separable operation. In case of not too strong

    Range range(0, dsize.height);

    int bufstep = (int)alignSize(dsize.width, 16);
    AutoBuffer<buf_type> _buffer(bufstep*ksize);
    const value_type* srows[MAX_ESIZE] = { 0 };
    buf_type* rows[MAX_ESIZE] = { 0 };
    int prev_sy[MAX_ESIZE];

    for (int k = 0; k < ksize; k++) {
        prev_sy[k] = -1;
        rows[k] = (buf_type*)_buffer + bufstep*k;
    }

    const alpha_type* beta = (const alpha_type*)_beta + ksize * range.start;

    HResizeLinear<value_type, buf_type, alpha_type> hresize;
    VResizeLinear<value_type, buf_type, alpha_type, FixedPtCast<int, uchar, INTER_RESIZE_COEF_BITS * 2>> vresize1;
    VResizeLinear<value_type, buf_type, alpha_type, Cast<float, float>> vresize2;

    for (dy = range.start; dy < range.end; dy++, beta += ksize) {
        int sy0 = yofs[dy], k0 = ksize, k1 = 0, ksize2 = ksize / 2;

        for (int k = 0; k < ksize; k++) {
            int sy = clip<int>(sy0 - ksize2 + 1 + k, 0, ssize.height);
            for (k1 = std::max(k1, k); k1 < ksize; k1++) {
                if (sy == prev_sy[k1]) { // if the sy-th row has been computed already, reuse it.
                    if (k1 > k) {
                        memcpy(rows[k], rows[k1], bufstep*sizeof(rows[0][0]));
                    }
                    break;
                }
            }
            if (k1 == ksize) {
                k0 = std::min(k0, k); // remember the first row that needs to be computed
            }
            srows[k] = (const value_type*)src.ptr(sy);
            prev_sy[k] = sy;
        }

        if (k0 < ksize) {
            hresize((const value_type**)(srows + k0), (buf_type**)(rows + k0), ksize - k0, xofs, (const alpha_type*)(_alpha),
                ssize.width, dsize.width, cn, xmin, xmax, ONE);
        }
        if (sizeof(_Tp) == 1) { // uchar
            vresize1((const buf_type**)rows, (value_type*)(dst.data + dst.step*dy), beta, dsize.width);
        } else { // float
            vresize2((const buf_type**)rows, (value_type*)(dst.data + dst.step*dy), beta, dsize.width);
        }
    }
}

template<typename _Tp, typename value_type, typename buf_type, typename alpha_type, int chs>
static void resizeGeneric_Cubic(const Mat_<_Tp, chs>& src, Mat_<_Tp, chs>& dst,
    const int* xofs, const void* _alpha, const int* yofs, const void* _beta, int xmin, int xmax, int ksize)
{
    Size ssize = src.size(), dsize = dst.size();
    int dy, cn = src.channels;
    ssize.width *= cn;
    dsize.width *= cn;
    xmin *= cn;
    xmax *= cn;
    // image resize is a separable operation. In case of not too strong

    Range range(0, dsize.height);

    int bufstep = (int)alignSize(dsize.width, 16);
    AutoBuffer<buf_type> _buffer(bufstep*ksize);
    const value_type* srows[MAX_ESIZE] = { 0 };
    buf_type* rows[MAX_ESIZE] = { 0 };
    int prev_sy[MAX_ESIZE];

    for (int k = 0; k < ksize; k++) {
        prev_sy[k] = -1;
        rows[k] = (buf_type*)_buffer + bufstep*k;
    }

    const alpha_type* beta = (const alpha_type*)_beta + ksize * range.start;

    HResizeCubic<value_type, buf_type, alpha_type> hresize;
    VResizeCubic<value_type, buf_type, alpha_type, FixedPtCast<int, uchar, INTER_RESIZE_COEF_BITS * 2>> vresize1;
    VResizeCubic<value_type, buf_type, alpha_type, Cast<float, float>> vresize2;

    for (dy = range.start; dy < range.end; dy++, beta += ksize) {
        int sy0 = yofs[dy], k0 = ksize, k1 = 0, ksize2 = ksize / 2;

        for (int k = 0; k < ksize; k++) {
            int sy = clip<int>(sy0 - ksize2 + 1 + k, 0, ssize.height);
            for (k1 = std::max(k1, k); k1 < ksize; k1++) {
                if (sy == prev_sy[k1]) { // if the sy-th row has been computed already, reuse it.
                    if (k1 > k) {
                        memcpy(rows[k], rows[k1], bufstep*sizeof(rows[0][0]));
                    }
                    break;
                }
            }
            if (k1 == ksize) {
                k0 = std::min(k0, k); // remember the first row that needs to be computed
            }
            srows[k] = (const value_type*)src.ptr(sy);
            prev_sy[k] = sy;
        }

        if (k0 < ksize) {
            hresize((const value_type**)(srows + k0), (buf_type**)(rows + k0), ksize - k0, xofs, (const alpha_type*)(_alpha),
                ssize.width, dsize.width, cn, xmin, xmax);
        }
        if (sizeof(_Tp) == 1) { // uchar
            vresize1((const buf_type**)rows, (value_type*)(dst.data + dst.step*dy), beta, dsize.width);
        } else { // float
            vresize2((const buf_type**)rows, (value_type*)(dst.data + dst.step*dy), beta, dsize.width);
        }
    }
}

template<typename _Tp, typename value_type, typename buf_type, typename alpha_type, int chs>
static void resizeGeneric_Lanczos4(const Mat_<_Tp, chs>& src, Mat_<_Tp, chs>& dst,
    const int* xofs, const void* _alpha, const int* yofs, const void* _beta, int xmin, int xmax, int ksize)
{
    Size ssize = src.size(), dsize = dst.size();
    int dy, cn = src.channels;
    ssize.width *= cn;
    dsize.width *= cn;
    xmin *= cn;
    xmax *= cn;
    // image resize is a separable operation. In case of not too strong

    Range range(0, dsize.height);

    int bufstep = (int)alignSize(dsize.width, 16);
    AutoBuffer<buf_type> _buffer(bufstep*ksize);
    const value_type* srows[MAX_ESIZE] = { 0 };
    buf_type* rows[MAX_ESIZE] = { 0 };
    int prev_sy[MAX_ESIZE];

    for (int k = 0; k < ksize; k++) {
        prev_sy[k] = -1;
        rows[k] = (buf_type*)_buffer + bufstep*k;
    }

    const alpha_type* beta = (const alpha_type*)_beta + ksize * range.start;

    HResizeLanczos4<value_type, buf_type, alpha_type> hresize;
    VResizeLanczos4<value_type, buf_type, alpha_type, FixedPtCast<int, uchar, INTER_RESIZE_COEF_BITS * 2>> vresize1;
    VResizeLanczos4<value_type, buf_type, alpha_type, Cast<float, float>> vresize2;

    for (dy = range.start; dy < range.end; dy++, beta += ksize) {
        int sy0 = yofs[dy], k0 = ksize, k1 = 0, ksize2 = ksize / 2;

        for (int k = 0; k < ksize; k++) {
            int sy = clip<int>(sy0 - ksize2 + 1 + k, 0, ssize.height);
            for (k1 = std::max(k1, k); k1 < ksize; k1++) {
                if (sy == prev_sy[k1]) { // if the sy-th row has been computed already, reuse it.
                    if (k1 > k) {
                        memcpy(rows[k], rows[k1], bufstep*sizeof(rows[0][0]));
                    }
                    break;
                }
            }
            if (k1 == ksize) {
                k0 = std::min(k0, k); // remember the first row that needs to be computed
            }
            srows[k] = (const value_type*)src.ptr(sy);
            prev_sy[k] = sy;
        }

        if (k0 < ksize) {
            hresize((const value_type**)(srows + k0), (buf_type**)(rows + k0), ksize - k0, xofs, (const alpha_type*)(_alpha),
                ssize.width, dsize.width, cn, xmin, xmax);
        }
        if (sizeof(_Tp) == 1) { // uchar
            vresize1((const buf_type**)rows, (value_type*)(dst.data + dst.step*dy), beta, dsize.width);
        }
        else { // float
            vresize2((const buf_type**)rows, (value_type*)(dst.data + dst.step*dy), beta, dsize.width);
        }
    }

}

template<typename _Tp, typename T, typename WT, int chs>
static void resizeGeneric_Area(const Mat_<_Tp, chs>& src, Mat_<_Tp, chs>& dst,
    const DecimateAlpha* xtab0, int xtab_size0, const DecimateAlpha* ytab, int ytab_size, const int* tabofs)
{
    Size dsize = dst.size();
    int cn = dst.channels;
    Range range(0, dsize.height);
    dsize.width *= cn;
    AutoBuffer<WT> _buffer(dsize.width * 2);
    const DecimateAlpha* xtab = xtab0;
    int xtab_size = xtab_size0;
    WT *buf = _buffer, *sum = buf + dsize.width;
    int j_start = tabofs[range.start], j_end = tabofs[range.end], j, k, dx, prev_dy = ytab[j_start].di;

    for (dx = 0; dx < dsize.width; dx++) {
        sum[dx] = (WT)0;
    }

    for (j = j_start; j < j_end; j++) {
        WT beta = ytab[j].alpha;
        int dy = ytab[j].di;
        int sy = ytab[j].si;

        const T* S = (const T*)src.ptr(sy);
        for (dx = 0; dx < dsize.width; dx++) {
            buf[dx] = (WT)0;
        }

        if (cn == 1) {
            for (k = 0; k < xtab_size; k++) {
                int dxn = xtab[k].di;
                WT alpha = xtab[k].alpha;
                buf[dxn] += S[xtab[k].si] * alpha;
            }
        } else if (cn == 2) {
            for (k = 0; k < xtab_size; k++) {
                int sxn = xtab[k].si;
                int dxn = xtab[k].di;
                WT alpha = xtab[k].alpha;
                WT t0 = buf[dxn] + S[sxn] * alpha;
                WT t1 = buf[dxn + 1] + S[sxn + 1] * alpha;
                buf[dxn] = t0; buf[dxn + 1] = t1;
            }
        } else if (cn == 3) {
            for (k = 0; k < xtab_size; k++) {
                int sxn = xtab[k].si;
                int dxn = xtab[k].di;
                WT alpha = xtab[k].alpha;
                WT t0 = buf[dxn] + S[sxn] * alpha;
                WT t1 = buf[dxn + 1] + S[sxn + 1] * alpha;
                WT t2 = buf[dxn + 2] + S[sxn + 2] * alpha;
                buf[dxn] = t0; buf[dxn + 1] = t1; buf[dxn + 2] = t2;
            }
        } else if (cn == 4) {
            for (k = 0; k < xtab_size; k++) {
                int sxn = xtab[k].si;
                int dxn = xtab[k].di;
                WT alpha = xtab[k].alpha;
                WT t0 = buf[dxn] + S[sxn] * alpha;
                WT t1 = buf[dxn + 1] + S[sxn + 1] * alpha;
                buf[dxn] = t0; buf[dxn + 1] = t1;
                t0 = buf[dxn + 2] + S[sxn + 2] * alpha;
                t1 = buf[dxn + 3] + S[sxn + 3] * alpha;
                buf[dxn + 2] = t0; buf[dxn + 3] = t1;
            }
        } else {
            for (k = 0; k < xtab_size; k++) {
                int sxn = xtab[k].si;
                int dxn = xtab[k].di;
                WT alpha = xtab[k].alpha;
                for (int c = 0; c < cn; c++)
                    buf[dxn + c] += S[sxn + c] * alpha;
            }
        }

        if (dy != prev_dy) {
            T* D = (T*)dst.ptr(prev_dy);

            for (dx = 0; dx < dsize.width; dx++) {
                D[dx] = saturate_cast<T>(sum[dx]);
                sum[dx] = beta*buf[dx];
            }
            prev_dy = dy;
        } else {
            for (dx = 0; dx < dsize.width; dx++) {
                sum[dx] += beta*buf[dx];
            }
        }
    }

    T* D = (T*)dst.ptr(prev_dy);
    for (dx = 0; dx < dsize.width; dx++) {
        D[dx] = saturate_cast<T>(sum[dx]);
    }
}

template<typename _Tp, typename T, typename WT, int chs>
static void resizeGeneric_AreaFast(const Mat_<_Tp, chs>& src, Mat_<_Tp, chs>& dst,
    const int* ofs, const int* xofs, int scale_x, int scale_y)
{
    Size ssize = src.size(), dsize = dst.size();
    int cn = src.channels;
    Range range(0, dsize.height);
    int area = scale_x*scale_y;
    float scale = 1.f / (area);
    int dwidth1 = (ssize.width / scale_x)*cn;
    dsize.width *= cn;
    ssize.width *= cn;
    int dy, dx, k = 0;

    ResizeAreaFastVec<uchar> vop(scale_x, scale_y, src.channels, (int)src.step);

    for (dy = range.start; dy < range.end; dy++) {
        T* D = (T*)(dst.data + dst.step*dy);
        int sy0 = dy*scale_y;
        int w = sy0 + scale_y <= ssize.height ? dwidth1 : 0;

        if (sy0 >= ssize.height) {
            for (dx = 0; dx < dsize.width; dx++) {
                D[dx] = 0;
            }
            continue;
        }

        dx = sizeof(_Tp) == 1 ? vop(src.ptr(sy0), (uchar*)D, w) : 0;
        for (; dx < w; dx++) {
            const T* S = (const T*)src.ptr(sy0) +xofs[dx];
            WT sum = 0;
            k = 0;

            for (; k <= area - 4; k += 4) {
                sum += S[ofs[k]] + S[ofs[k + 1]] + S[ofs[k + 2]] + S[ofs[k + 3]];
            }

            for (; k < area; k++) {
                sum += S[ofs[k]];
            }

            D[dx] = saturate_cast<T>(sum * scale);
        }

        for (; dx < dsize.width; dx++) {
            WT sum = 0;
            int count = 0, sx0 = xofs[dx];
            if (sx0 >= ssize.width) {
                D[dx] = 0;
            }

            for (int sy = 0; sy < scale_y; sy++) {
                if (sy0 + sy >= ssize.height) {
                    break;
                }
                const T* S = (const T*)src.ptr(sy0 + sy) + sx0;
                for (int sx = 0; sx < scale_x*cn; sx += cn) {
                    if (sx0 + sx >= ssize.width) {
                        break;
                    }
                    sum += S[sx];
                    count++;
                }
            }

            D[dx] = saturate_cast<T>((float)sum / count);
        }
    }
}

template<typename _Tp>
static void interpolateCubic(_Tp x, _Tp* coeffs)
{
    const float A = -0.75f;

    coeffs[0] = ((A*(x + 1) - 5 * A)*(x + 1) + 8 * A)*(x + 1) - 4 * A;
    coeffs[1] = ((A + 2)*x - (A + 3))*x*x + 1;
    coeffs[2] = ((A + 2)*(1 - x) - (A + 3))*(1 - x)*(1 - x) + 1;
    coeffs[3] = 1.f - coeffs[0] - coeffs[1] - coeffs[2];
}

template<typename _Tp>
static void interpolateLanczos4(_Tp x, _Tp* coeffs)
{
    static const double s45 = 0.70710678118654752440084436210485;
    static const double cs[][2] = { { 1, 0 }, { -s45, -s45 }, { 0, 1 }, { s45, -s45 }, { -1, 0 }, { s45, s45 }, { 0, -1 }, { -s45, s45 } };

    if (x < FLT_EPSILON) {
        for (int i = 0; i < 8; i++) {
            coeffs[i] = 0;
        }
        coeffs[3] = 1;
        return;
    }

    float sum = 0;
    double y0 = -(x + 3)*FBC_PI*0.25, s0 = sin(y0), c0 = cos(y0);
    for (int i = 0; i < 8; i++) {
        double y = -(x + 3 - i)*FBC_PI*0.25;
        coeffs[i] = (float)((cs[i][0] * s0 + cs[i][1] * c0) / (y*y));
        sum += coeffs[i];
    }

    sum = 1.f / sum;
    for (int i = 0; i < 8; i++) {
        coeffs[i] *= sum;
    }
}

template<typename _Tp, int chs>
static int resize_nearest(const Mat_<_Tp, chs>& src, Mat_<_Tp, chs>& dst)
{
    Size ssize = src.size();
    Size dsize = dst.size();

    double fx = (double)dsize.width / ssize.width;
    double fy = (double)dsize.height / ssize.height;

    AutoBuffer<int> _x_ofs(dsize.width);
    int* x_ofs = _x_ofs;
    int pix_size = (int)src.elemSize();
    int pix_size4 = (int)(pix_size / sizeof(int));
    double ifx = 1. / fx, ify = 1. / fy;

    for (int x = 0; x < dsize.width; x++) {
        int sx = fbcFloor(x*ifx);
        x_ofs[x] = std::min(sx, ssize.width - 1)*pix_size;
    }

    Range range(0, dsize.height);
    int x, y;

    for (y = range.start; y < range.end; y++) {
        uchar* D = dst.data + dst.step*y;
        int sy = std::min(fbcFloor(y*ify), ssize.height - 1);
        const uchar* S = src.ptr(sy);

        switch (pix_size) {
        case 1:
            for (x = 0; x <= dsize.width - 2; x += 2) {
                uchar t0 = S[x_ofs[x]];
                uchar t1 = S[x_ofs[x + 1]];
                D[x] = t0;
                D[x + 1] = t1;
            }

            for (; x < dsize.width; x++) {
                D[x] = S[x_ofs[x]];
            }
            break;
        case 2:
            for (x = 0; x < dsize.width; x++) {
                *(ushort*)(D + x * 2) = *(ushort*)(S + x_ofs[x]);
            }
            break;
        case 3:
            for (x = 0; x < dsize.width; x++, D += 3) {
                const uchar* _tS = S + x_ofs[x];
                D[0] = _tS[0]; D[1] = _tS[1]; D[2] = _tS[2];
            }
            break;
        case 4:
            for (x = 0; x < dsize.width; x++) {
                *(int*)(D + x * 4) = *(int*)(S + x_ofs[x]);
            }
            break;
        case 6:
            for (x = 0; x < dsize.width; x++, D += 6) {
                const ushort* _tS = (const ushort*)(S + x_ofs[x]);
                ushort* _tD = (ushort*)D;
                _tD[0] = _tS[0]; _tD[1] = _tS[1]; _tD[2] = _tS[2];
            }
            break;
        case 8:
            for (x = 0; x < dsize.width; x++, D += 8) {
                const int* _tS = (const int*)(S + x_ofs[x]);
                int* _tD = (int*)D;
                _tD[0] = _tS[0]; _tD[1] = _tS[1];
            }
            break;
        case 12:
            for (x = 0; x < dsize.width; x++, D += 12) {
                const int* _tS = (const int*)(S + x_ofs[x]);
                int* _tD = (int*)D;
                _tD[0] = _tS[0]; _tD[1] = _tS[1]; _tD[2] = _tS[2];
            }
            break;
        default:
            for (x = 0; x < dsize.width; x++, D += pix_size) {
                const int* _tS = (const int*)(S + x_ofs[x]);
                int* _tD = (int*)D;
                for (int k = 0; k < pix_size4; k++)
                    _tD[k] = _tS[k];
            }
        }
    }

    return 0;
}

template<typename _Tp, int chs>
static int resize_linear(const Mat_<_Tp, chs>& src, Mat_<_Tp, chs>& dst)
{
    Size ssize = src.size();
    Size dsize = dst.size();

    double inv_scale_x = (double)dsize.width / ssize.width;
    double inv_scale_y = (double)dsize.height / ssize.height;
    double scale_x = 1. / inv_scale_x, scale_y = 1. / inv_scale_y;

    int iscale_x = saturate_cast<int>(scale_x);
    int iscale_y = saturate_cast<int>(scale_y);

    bool is_area_fast = std::abs(scale_x - iscale_x) < DBL_EPSILON && std::abs(scale_y - iscale_y) < DBL_EPSILON;
    // in case of scale_x && scale_y is equal to 2
    // INTER_AREA (fast) also is equal to INTER_LINEAR
    if (is_area_fast && iscale_x == 2 && iscale_y == 2) {
        resize_area(src, dst);
        return 0;
    }

    int cn = dst.channels;
    int k, sx, sy, dx, dy;
    int xmin = 0, xmax = dsize.width, width = dsize.width*cn;
    bool fixpt = sizeof(_Tp) == 1 ? true : false;
    float fx, fy;
    int ksize = 2, ksize2;
    ksize2 = ksize / 2;

    AutoBuffer<uchar> _buffer((width + dsize.height)*(sizeof(int) + sizeof(float)*ksize));
    int* xofs = (int*)(uchar*)_buffer;
    int* yofs = xofs + width;
    float* alpha = (float*)(yofs + dsize.height);
    short* ialpha = (short*)alpha;
    float* beta = alpha + width*ksize;
    short* ibeta = ialpha + width*ksize;
    float cbuf[MAX_ESIZE];

    for (dx = 0; dx < dsize.width; dx++) {
        fx = (float)((dx + 0.5)*scale_x - 0.5);
        sx = fbcFloor(fx);
        fx -= sx;

        if (sx < ksize2 - 1) {
            xmin = dx + 1;
            if (sx < 0) {
                fx = 0, sx = 0;
            }
        }

        if (sx + ksize2 >= ssize.width) {
            xmax = std::min(xmax, dx);
            if (sx >= ssize.width - 1) {
                fx = 0, sx = ssize.width - 1;
            }
        }

        for (k = 0, sx *= cn; k < cn; k++) {
            xofs[dx*cn + k] = sx + k;
        }

        cbuf[0] = 1.f - fx;
        cbuf[1] = fx;

        if (fixpt) {
            for (k = 0; k < ksize; k++) {
                ialpha[dx*cn*ksize + k] = saturate_cast<short>(cbuf[k] * INTER_RESIZE_COEF_SCALE);
            }
            for (; k < cn*ksize; k++) {
                ialpha[dx*cn*ksize + k] = ialpha[dx*cn*ksize + k - ksize];
            }
        } else {
            for (k = 0; k < ksize; k++) {
                alpha[dx*cn*ksize + k] = cbuf[k];
            }
            for (; k < cn*ksize; k++) {
                alpha[dx*cn*ksize + k] = alpha[dx*cn*ksize + k - ksize];
            }
        }
    }

    for (dy = 0; dy < dsize.height; dy++) {
        fy = (float)((dy + 0.5)*scale_y - 0.5);
        sy = fbcFloor(fy);
        fy -= sy;

        yofs[dy] = sy;
        cbuf[0] = 1.f - fy;
        cbuf[1] = fy;

        if (fixpt) {
            for (k = 0; k < ksize; k++) {
                ibeta[dy*ksize + k] = saturate_cast<short>(cbuf[k] * INTER_RESIZE_COEF_SCALE);
            }
        } else {
            for (k = 0; k < ksize; k++) {
                beta[dy*ksize + k] = cbuf[k];
            }
        }
    }

    if (sizeof(_Tp) == 1) { // uchar
        typedef uchar value_type; // HResizeLinear/VResizeLinear
        typedef int buf_type;
        typedef short alpha_type;
        int ONE = INTER_RESIZE_COEF_SCALE;

        resizeGeneric_Linear<_Tp, value_type, buf_type, alpha_type, chs>(src, dst,
            xofs, fixpt ? (void*)ialpha : (void*)alpha, yofs, fixpt ? (void*)ibeta : (void*)beta, xmin, xmax, ksize, ONE);
    } else if (sizeof(_Tp) == 4) { // float
        typedef float value_type; // HResizeLinear/VResizeLinear
        typedef float buf_type;
        typedef float alpha_type;
        int ONE = 1;

        resizeGeneric_Linear<_Tp, value_type, buf_type, alpha_type, chs>(src, dst,
            xofs, fixpt ? (void*)ialpha : (void*)alpha, yofs, fixpt ? (void*)ibeta : (void*)beta, xmin, xmax, ksize, ONE);
    } else {
        fprintf(stderr, "not support type\n");
        return -1;
    }

    return 0;
}

template<typename _Tp, int chs>
static int resize_cubic(const Mat_<_Tp, chs>& src, Mat_<_Tp, chs>& dst)
{
    Size ssize = src.size();
    Size dsize = dst.size();

    double inv_scale_x = (double)dsize.width / ssize.width;
    double inv_scale_y = (double)dsize.height / ssize.height;
    double scale_x = 1. / inv_scale_x, scale_y = 1. / inv_scale_y;

    int cn = dst.channels;
    int k, sx, sy, dx, dy;
    int xmin = 0, xmax = dsize.width, width = dsize.width*cn;
    bool fixpt = sizeof(_Tp) == 1 ? true : false;
    float fx, fy;
    int ksize = 4, ksize2;
    ksize2 = ksize / 2;

    AutoBuffer<uchar> _buffer((width + dsize.height)*(sizeof(int) + sizeof(float)*ksize));
    int* xofs = (int*)(uchar*)_buffer;
    int* yofs = xofs + width;
    float* alpha = (float*)(yofs + dsize.height);
    short* ialpha = (short*)alpha;
    float* beta = alpha + width*ksize;
    short* ibeta = ialpha + width*ksize;
    float cbuf[MAX_ESIZE];

    for (dx = 0; dx < dsize.width; dx++) {
        fx = (float)((dx + 0.5)*scale_x - 0.5);
        sx = fbcFloor(fx);
        fx -= sx;

        if (sx < ksize2 - 1) {
            xmin = dx + 1;
        }

        if (sx + ksize2 >= ssize.width) {
            xmax = std::min(xmax, dx);
        }

        for (k = 0, sx *= cn; k < cn; k++) {
            xofs[dx*cn + k] = sx + k;
        }

        interpolateCubic<float>(fx, cbuf);

        if (fixpt) {
            for (k = 0; k < ksize; k++) {
                ialpha[dx*cn*ksize + k] = saturate_cast<short>(cbuf[k] * INTER_RESIZE_COEF_SCALE);
            }
            for (; k < cn*ksize; k++) {
                ialpha[dx*cn*ksize + k] = ialpha[dx*cn*ksize + k - ksize];
            }
        } else {
            for (k = 0; k < ksize; k++) {
                alpha[dx*cn*ksize + k] = cbuf[k];
            }
            for (; k < cn*ksize; k++) {
                alpha[dx*cn*ksize + k] = alpha[dx*cn*ksize + k - ksize];
            }
        }
    }

    for (dy = 0; dy < dsize.height; dy++) {
        fy = (float)((dy + 0.5)*scale_y - 0.5);
        sy = cvFloor(fy);
        fy -= sy;

        yofs[dy] = sy;
        interpolateCubic<float>(fy, cbuf);

        if (fixpt) {
            for (k = 0; k < ksize; k++) {
                ibeta[dy*ksize + k] = saturate_cast<short>(cbuf[k] * INTER_RESIZE_COEF_SCALE);
            }
        } else {
            for (k = 0; k < ksize; k++) {
                beta[dy*ksize + k] = cbuf[k];
            }
        }
    }

    if (sizeof(_Tp) == 1) { // uchar
        typedef uchar value_type; // HResizeCubic/VResizeCubic
        typedef int buf_type;
        typedef short alpha_type;

        resizeGeneric_Cubic<_Tp, value_type, buf_type, alpha_type, chs>(src, dst,
            xofs, fixpt ? (void*)ialpha : (void*)alpha, yofs, fixpt ? (void*)ibeta : (void*)beta, xmin, xmax, ksize);
    } else if (sizeof(_Tp) == 4) { // float
        typedef float value_type; // HResizeCubic/VResizeCubic
        typedef float buf_type;
        typedef float alpha_type;

        resizeGeneric_Cubic<_Tp, value_type, buf_type, alpha_type, chs>(src, dst,
            xofs, fixpt ? (void*)ialpha : (void*)alpha, yofs, fixpt ? (void*)ibeta : (void*)beta, xmin, xmax, ksize);
    } else {
        fprintf(stderr, "not support type\n");
        return -1;
    }

    return 0;
}

template<typename _Tp, int chs>
static int resize_area(const Mat_<_Tp, chs>& src, Mat_<_Tp, chs>& dst)
{
    Size ssize = src.size();
    Size dsize = dst.size();
    int cn = dst.channels;

    double inv_scale_x = (double)dsize.width / ssize.width;
    double inv_scale_y = (double)dsize.height / ssize.height;
    double scale_x = 1. / inv_scale_x, scale_y = 1. / inv_scale_y;

    int iscale_x = saturate_cast<int>(scale_x);
    int iscale_y = saturate_cast<int>(scale_y);

    bool is_area_fast = std::abs(scale_x - iscale_x) < DBL_EPSILON && std::abs(scale_y - iscale_y) < DBL_EPSILON;

    int k, sx, sy, dx, dy;

    // true "area" interpolation is only implemented for the case (scale_x <= 1 && scale_y <= 1).
    // In other cases it is emulated using some variant of bilinear interpolation
    if (scale_x >= 1 && scale_y >= 1) {
        if (is_area_fast) {
            int area = iscale_x*iscale_y;
            size_t srcstep = src.step / sizeof(_Tp);
            AutoBuffer<int> _ofs(area + dsize.width*cn);
            int* ofs = _ofs;
            int* xofs = ofs + area;

            for (sy = 0, k = 0; sy < iscale_y; sy++) {
                for (sx = 0; sx < iscale_x; sx++) {
                    ofs[k++] = (int)(sy*srcstep + sx*cn);
                }
            }

            for (dx = 0; dx < dsize.width; dx++) {
                int j = dx * cn;
                sx = iscale_x * j;
                for (k = 0; k < cn; k++) {
                    xofs[j + k] = sx + k;
                }
            }

            if (sizeof(_Tp) == 1) { // uchar
                typedef uchar T;
                typedef int WT;

                resizeGeneric_AreaFast<_Tp, T, WT, chs>(src, dst, ofs, xofs, iscale_x, iscale_y);
            } else if (sizeof(_Tp) == 4) { // float
                typedef float T;
                typedef float WT;

                resizeGeneric_AreaFast<_Tp, T, WT, chs>(src, dst, ofs, xofs, iscale_x, iscale_y);
            } else {
                fprintf(stderr, "not support type\n");
                return -1;
            }

            return 0;
        }

        FBC_Assert(cn <= 4);

        AutoBuffer<DecimateAlpha> _xytab((ssize.width + ssize.height) * 2);
        DecimateAlpha* xtab = _xytab, *ytab = xtab + ssize.width * 2;

        int xtab_size = computeResizeAreaTab<int>(ssize.width, dsize.width, cn, scale_x, xtab);
        int ytab_size = computeResizeAreaTab<int>(ssize.height, dsize.height, 1, scale_y, ytab);

        AutoBuffer<int> _tabofs(dsize.height + 1);
        int* tabofs = _tabofs;
        for (k = 0, dy = 0; k < ytab_size; k++) {
            if (k == 0 || ytab[k].di != ytab[k - 1].di) {
                assert(ytab[k].di == dy);
                tabofs[dy++] = k;
            }
        }
        tabofs[dy] = ytab_size;

        if (sizeof(_Tp) == 1) { // uchar
            typedef uchar T;
            typedef float WT;

            resizeGeneric_Area<_Tp, T, WT, chs>(src, dst, xtab, xtab_size, ytab, ytab_size, tabofs);
        } else if (sizeof(_Tp) == 4) { // float
            typedef float T;
            typedef float WT;

            resizeGeneric_Area<_Tp, T, WT, chs>(src, dst, xtab, xtab_size, ytab, ytab_size, tabofs);
        } else {
            fprintf(stderr, "not support type\n");
            return -1;
        }

        return 0;
    }

    int xmin = 0, xmax = dsize.width, width = dsize.width*cn;
    bool fixpt = sizeof(_Tp) == 1 ? true : false;
    float fx, fy;
    int ksize = 2, ksize2;
    ksize2 = ksize / 2;

    AutoBuffer<uchar> _buffer((width + dsize.height)*(sizeof(int) + sizeof(float)*ksize));
    int* xofs = (int*)(uchar*)_buffer;
    int* yofs = xofs + width;
    float* alpha = (float*)(yofs + dsize.height);
    short* ialpha = (short*)alpha;
    float* beta = alpha + width*ksize;
    short* ibeta = ialpha + width*ksize;
    float cbuf[MAX_ESIZE];

    for (dx = 0; dx < dsize.width; dx++) {
        sx = fbcFloor(dx*scale_x);
        fx = (float)((dx + 1) - (sx + 1)*inv_scale_x);
        fx = fx <= 0 ? 0.f : fx - fbcFloor(fx);

        if (sx < ksize2 - 1) {
            xmin = dx + 1;
            if (sx < 0) {
                fx = 0, sx = 0;
            }
        }

        if (sx + ksize2 >= ssize.width) {
            xmax = std::min(xmax, dx);
            if (sx >= ssize.width - 1) {
                fx = 0, sx = ssize.width - 1;
            }
        }

        for (k = 0, sx *= cn; k < cn; k++) {
            xofs[dx*cn + k] = sx + k;
        }

        cbuf[0] = 1.f - fx;
        cbuf[1] = fx;

        if (fixpt) {
            for (k = 0; k < ksize; k++) {
                ialpha[dx*cn*ksize + k] = saturate_cast<short>(cbuf[k] * INTER_RESIZE_COEF_SCALE);
            }
            for (; k < cn*ksize; k++) {
                ialpha[dx*cn*ksize + k] = ialpha[dx*cn*ksize + k - ksize];
            }
        } else {
            for (k = 0; k < ksize; k++) {
                alpha[dx*cn*ksize + k] = cbuf[k];
            }
            for (; k < cn*ksize; k++) {
                alpha[dx*cn*ksize + k] = alpha[dx*cn*ksize + k - ksize];
            }
        }
    }

    for (dy = 0; dy < dsize.height; dy++) {
        sy = fbcFloor(dy*scale_y);
        fy = (float)((dy + 1) - (sy + 1)*inv_scale_y);
        fy = fy <= 0 ? 0.f : fy - fbcFloor(fy);

        yofs[dy] = sy;
        cbuf[0] = 1.f - fy;
        cbuf[1] = fy;

        if (fixpt) {
            for (k = 0; k < ksize; k++) {
                ibeta[dy*ksize + k] = saturate_cast<short>(cbuf[k] * INTER_RESIZE_COEF_SCALE);
            }
        } else {
            for (k = 0; k < ksize; k++) {
                beta[dy*ksize + k] = cbuf[k];
            }
        }
    }

    if (sizeof(_Tp) == 1) { // uchar
        typedef uchar value_type; // HResizeLinear/VResizeLinear
        typedef int buf_type;
        typedef short alpha_type;
        int ONE = INTER_RESIZE_COEF_SCALE;

        resizeGeneric_Linear<_Tp, value_type, buf_type, alpha_type, chs>(src, dst,
            xofs, fixpt ? (void*)ialpha : (void*)alpha, yofs, fixpt ? (void*)ibeta : (void*)beta, xmin, xmax, ksize, ONE);
    } else if (sizeof(_Tp) == 4) { // float
        typedef float value_type; // HResizeLinear/VResizeLinear
        typedef float buf_type;
        typedef float alpha_type;
        int ONE = 1;

        resizeGeneric_Linear<_Tp, value_type, buf_type, alpha_type, chs>(src, dst,
            xofs, fixpt ? (void*)ialpha : (void*)alpha, yofs, fixpt ? (void*)ibeta : (void*)beta, xmin, xmax, ksize, ONE);
    } else {
        fprintf(stderr, "not support type\n");
        return -1;
    }

    return 0;
}

template<typename _Tp, int chs>
static int resize_lanczos4(const Mat_<_Tp, chs>& src, Mat_<_Tp, chs>& dst)
{
    Size ssize = src.size();
    Size dsize = dst.size();

    double inv_scale_x = (double)dsize.width / ssize.width;
    double inv_scale_y = (double)dsize.height / ssize.height;
    double scale_x = 1. / inv_scale_x, scale_y = 1. / inv_scale_y;

    int cn = dst.channels;
    int k, sx, sy, dx, dy;
    int xmin = 0, xmax = dsize.width, width = dsize.width*cn;
    bool fixpt = sizeof(_Tp) == 1 ? true : false;
    float fx, fy;
    int ksize = 8, ksize2;
    ksize2 = ksize / 2;

    AutoBuffer<uchar> _buffer((width + dsize.height)*(sizeof(int) + sizeof(float)*ksize));
    int* xofs = (int*)(uchar*)_buffer;
    int* yofs = xofs + width;
    float* alpha = (float*)(yofs + dsize.height);
    short* ialpha = (short*)alpha;
    float* beta = alpha + width*ksize;
    short* ibeta = ialpha + width*ksize;
    float cbuf[MAX_ESIZE];

    for (dx = 0; dx < dsize.width; dx++) {
        fx = (float)((dx + 0.5)*scale_x - 0.5);
        sx = fbcFloor(fx);
        fx -= sx;

        if (sx < ksize2 - 1) {
            xmin = dx + 1;
        }

        if (sx + ksize2 >= ssize.width) {
            xmax = std::min(xmax, dx);
        }

        for (k = 0, sx *= cn; k < cn; k++) {
            xofs[dx*cn + k] = sx + k;
        }

        interpolateLanczos4<float>(fx, cbuf);

        if (fixpt) {
            for (k = 0; k < ksize; k++)
                ialpha[dx*cn*ksize + k] = saturate_cast<short>(cbuf[k] * INTER_RESIZE_COEF_SCALE);
            for (; k < cn*ksize; k++)
                ialpha[dx*cn*ksize + k] = ialpha[dx*cn*ksize + k - ksize];
        } else {
            for (k = 0; k < ksize; k++)
                alpha[dx*cn*ksize + k] = cbuf[k];
            for (; k < cn*ksize; k++)
                alpha[dx*cn*ksize + k] = alpha[dx*cn*ksize + k - ksize];
        }
    }

    for (dy = 0; dy < dsize.height; dy++) {
        fy = (float)((dy + 0.5)*scale_y - 0.5);
        sy = fbcFloor(fy);
        fy -= sy;

        yofs[dy] = sy;

        interpolateLanczos4<float>(fy, cbuf);

        if (fixpt){
            for (k = 0; k < ksize; k++)
                ibeta[dy*ksize + k] = saturate_cast<short>(cbuf[k] * INTER_RESIZE_COEF_SCALE);
        } else {
            for (k = 0; k < ksize; k++)
                beta[dy*ksize + k] = cbuf[k];
        }
    }

    if (sizeof(_Tp) == 1) { // uchar
        typedef uchar value_type; // HResizeLanczos4/VResizeLanczos4
        typedef int buf_type;
        typedef short alpha_type;

        resizeGeneric_Lanczos4<_Tp, value_type, buf_type, alpha_type, chs>(src, dst,
            xofs, fixpt ? (void*)ialpha : (void*)alpha, yofs, fixpt ? (void*)ibeta : (void*)beta, xmin, xmax, ksize);
    } else if (sizeof(_Tp) == 4) { // float
        typedef float value_type; // HResizeLanczos4/VResizeLanczos4
        typedef float buf_type;
        typedef float alpha_type;

        resizeGeneric_Lanczos4<_Tp, value_type, buf_type, alpha_type, chs>(src, dst,
            xofs, fixpt ? (void*)ialpha : (void*)alpha, yofs, fixpt ? (void*)ibeta : (void*)beta, xmin, xmax, ksize);
    } else {
        fprintf(stderr, "not support type\n");
        return -1;
    }

    return 0;
}

} // namespace fbc

#endif // FBC_CV_RESIZE_HPP_