inline void rgb_to_yuv(unsigned char   b, unsigned char   g, unsigned char   r,

                       unsigned char & y, unsigned char & u, unsigned char & v)

{

    float yf, uf, vf;

    //Y = R * 0.299 + G * 0.587 + B * 0.114;

    //U = R * -0.169 + G * -0.332 + B * 0.500 + 128.0;

    //V = R * 0.500 + G * -0.419 + B * -0.0813 + 128.0;

    yf =    0.299f * static_cast<float>(r) +

            0.587f * static_cast<float>(g) +

            0.114f * static_cast<float>(b);

    yf = (yf > 255.0f) ? 255.0f: yf;

    yf = (yf < 0.0f) ? 0.0f: yf;

    y = static_cast<unsigned char>(yf);

    uf =   -0.169f * static_cast<float>(r) -

            0.332f * static_cast<float>(g) +

            0.500f * static_cast<float>(b) + 128.0;

    uf = (uf > 255.0f) ? 255.0f: uf;

    uf = (uf < 0.0f) ? 0.0f: uf;

    u = static_cast<unsigned char>(uf);

    vf =    0.500f * static_cast<float>(r) -

            0.419f * static_cast<float>(g) -

            0.081f * static_cast<float>(b) + 128.0;

    vf = (vf > 255.0f) ? 255.0f: vf;

    vf = (vf < 0.0f) ? 0.0f: vf;

    v = static_cast<unsigned char>(vf);

}

void RGB_to_YUV420(const unsigned char * rgb, unsigned char * yuv420, int width, int height)

{

    unsigned char * y_pixel = yuv420;

    unsigned char * u_pixel = yuv420 + width * height;

    unsigned char * v_pixel = yuv420 + width * height + (width * height / 4);

    unsigned char * U_tmp = new unsigned char [width * height];

    unsigned char * V_tmp = new unsigned char [width * height];

    int index = 0;

    for (int y = 0; y < height; ++y)

    {

        for (int x = 0; x < width; ++x)

        {

            rgb_to_yuv(rgb[3 * (y * width + x) + 0], rgb[3 * (y * width + x) + 1], rgb[3 * (y * width + x) + 2], y_pixel[index], U_tmp[index], V_tmp[index]);

            index++;

        }

    }

    index = 0;

    for (int y = 0; y < height; y+=2)

    {

        for (int x = 0; x < width; x+=2)

        {

            u_pixel[index] = U_tmp[y * width + x];

            v_pixel[index] = V_tmp[y * width + x];

            index++;

        }

    }

    delete [] U_tmp;

    delete [] V_tmp;

}