YUY2和RGB转换

YUY2经常用于电视制式以及许多摄像头的输出格式.而我们在处理时经常需要将其转化为RGB进行处理,这里简单介绍下YUY2(YUV)与RGB之间相互转化的关系:

http://msdn2.microsoft.com/en-us/library/ms893078.aspx

 

YUY2(YUV) To RGB:

C = Y - 16

D = U - 128

E = V - 128

R = clip(( 298 * C + 409 * E + 128) >> 8) G = clip(( 298 * C - 100 * D - 208 * E + 128) >> 8) B = clip(( 298 * C + 516 * D + 128) >> 8)

其中 clip()为限制函数,将其取值限制在0-255之间.

 

RGB To YUY2(YUV):

Y = ( ( 66 * R + 129 * G + 25 * B + 128) >> 8) + 16 U = ( ( -38 * R - 74 * G + 112 * B + 128) >> 8) + 128 V = ( ( 112 * R - 94 * G - 18 * B + 128) >> 8) + 128 上述两个公式在代码中的 int YUV2RGB(void* pYUV, void* pRGB, int width, int height, bool alphaYUV, bool alphaRGB); int RGB2YUV(void* pRGB, void* pYUVX, int width, int height, bool alphaYUV, bool alphaRGB); 函数中转换。 在诸如摄像头的数据获取中，我们往往需要直接在YUY2(YUV)空间上进行一些图象处理，我们希望能够在YUY2 (YUV)进行一些RGB上可以做到的处理。这里已blending为例，将两张带有透明度的YUY2(YUV)图片进行叠加，
以达到在RGB空间进行图像合成的效果。

RGB空间进行图像叠加，通常背景（BG）是不透明的，而前景（FG）是带有透明度的。在RGB空间，可以简单表示为：
Rdest = Rfg*alpha + Rbg*(1-alpha);
Gdest = Gfg*alpha + Gbg*(1-alpha);
Bdest = Bfg*alpha + Bbg*(1-alpha);
// Rdest、Gdest、Bdest 为最终合成后的像素值

考虑到
Y = ( ( 66 * R + 129 * G + 25 * B + 128) >> 8) + 16 U = ( ( -38 * R - 74 * G + 112 * B + 128) >> 8) + 128 V = ( ( 112 * R - 94 * G - 18 * B + 128) >> 8) + 128 我们可以推导出

(Ydest-16)<<8 = ((Yfg-16)<<8)*alpha + ((Ybg-16)<<8)*(1-alpha);
(Udest-128)<<8 = ((Ufg-128)<<8)*alpha + ((Ubg-128)<<8)*(1-alpha);
(Vdest-128)<<8 = ((Vfg-128)<<8)*alpha + ((Vbg-128)<<8)*(1-alpha);

从而可以得到
Ydest = (Yfg-16)*alpha + (Ybg-16)*(1-alpha) + 16;
Udest = (Ufg-128)*alpha + (Ubg-128)*(1-alpha) + 128;
Vdest = (Vfg-128)*alpha + (Vbg-128)*(1-alpha) + 128;

这个叠加过程在函数
int YUVBlending(void* pBGYUV, void* pFGYUV, int width, int height, bool alphaBG, bool alphaFG)
中实现。

由于本文针对摄像头采集所得的数据进行处理，因此数据为YUY2格式，即4个字节来表示两个像素点的YUV信息，
排列为Y1 U1 Y2 V2， 对于像素点1为(Y1, U1, V1)，像素点2为(Y2, U1, V1)。即两个像素点共用U、V信息。

这里假设带有alpha透明度的YUV格式用6个字节来表示两个像素点的YUV以及alpha信息，排列为 Y1 U1 Y2 V1 alpha1 alpha2
其中像素点1为(Y1, U1, V1, alpha1)，像素点2为(Y2, U1, V1, alpha2)。其中alpha为对应点的透明度信息。

而带有alpha透明度RGB格式的图片，假设为32bits的BMP图片，每个像素点用4bytes来表示，分别为B G R alpha信息。

上述函数的具体实现为：

  
  
  
  
//////////////////////////////////////////////////////////////////////////
// YUV2RGB
// pYUV         point to the YUV data
// pRGB         point to the RGB data
// width        width of the picture
// height       height of the picture
// alphaYUV     is there an alpha channel in YUV
// alphaRGB     is there an alpha channel in RGB
//////////////////////////////////////////////////////////////////////////
int YUV2RGB(void* pYUV, void* pRGB, int width, int height, bool alphaYUV, bool alphaRGB)
{
    if (NULL == pYUV)
    {
        return -1;
    }
    unsigned char* pYUVData = (unsigned char *)pYUV;
    unsigned char* pRGBData = (unsigned char *)pRGB;
    if (NULL == pRGBData)
    {
        if (alphaRGB)
        {
            pRGBData = new unsigned char[width*height*4];
        }
        else
            pRGBData = new unsigned char[width*height*3];
    }
    int Y1, U1, V1, Y2, alpha1, alpha2, R1, G1, B1, R2, G2, B2;
    int C1, D1, E1, C2;
    if (alphaRGB)
    {
        if (alphaYUV)
        {
            for (int i=0; i<height; ++i)
            {
                for (int j=0; j<width/2; ++j)
                {
                    Y1 = *(pYUVData+i*width*3+j*6);
                    U1 = *(pYUVData+i*width*3+j*6+1);
                    Y2 = *(pYUVData+i*width*3+j*6+2);
                    V1 = *(pYUVData+i*width*3+j*6+3);
                    alpha1 = *(pYUVData+i*width*3+j*6+4);
                    alpha2 = *(pYUVData+i*width*3+j*6+5);
                    C1 = Y1-16;
                    C2 = Y2-16;
                    D1 = U1-128;
                    E1 = V1-128;
                    R1 = ((298*C1 + 409*E1 + 128)>>8>255 ? 255 : (298*C1 + 409*E1 + 128)>>8);
                    G1 = ((298*C1 - 100*D1 - 208*E1 + 128)>>8>255 ? 255 : (298*C1 - 100*D1 - 208*E1 + 128)>>8);
                    B1 = ((298*C1+516*D1 +128)>>8>255 ? 255 : (298*C1+516*D1 +128)>>8);
                    R2 = ((298*C2 + 409*E1 + 128)>>8>255 ? 255 : (298*C2 + 409*E1 + 128)>>8);
                    G2 = ((298*C2 - 100*D1 - 208*E1 + 128)>>8>255 ? 255 : (298*C2 - 100*D1 - 208*E1 + 128)>>8);
                    B2 = ((298*C2 + 516*D1 +128)>>8>255 ? 255 : (298*C2 + 516*D1 +128)>>8);
                    *(pRGBData+(height-i-1)*width*4+j*8+2) = R1<0 ? 0 : R1;
                    *(pRGBData+(height-i-1)*width*4+j*8+1) = G1<0 ? 0 : G1;
                    *(pRGBData+(height-i-1)*width*4+j*8) = B1<0 ? 0 : B1;
                    *(pRGBData+(height-i-1)*width*4+j*8+3) = alpha1;
                    *(pRGBData+(height-i-1)*width*4+j*8+6) = R2<0 ? 0 : R2;
                    *(pRGBData+(height-i-1)*width*4+j*8+5) = G2<0 ? 0 : G2;
                    *(pRGBData+(height-i-1)*width*4+j*8+4) = B2<0 ? 0 : B2;
                    *(pRGBData+(height-i-1)*width*4+j*8+7) = alpha2;
                }
            }
        }
        else
        {
            int alpha = 255;
            for (int i=0; i<height; ++i)
            {
                for (int j=0; j<width/2; ++j)
                {
                    Y1 = *(pYUVData+i*width*2+j*4);
                    U1 = *(pYUVData+i*width*2+j*4+1);
                    Y2 = *(pYUVData+i*width*2+j*4+2);
                    V1 = *(pYUVData+i*width*2+j*4+3);
                    C1 = Y1-16;
                    C2 = Y2-16;
                    D1 = U1-128;
                    E1 = V1-128;
                    R1 = ((298*C1 + 409*E1 + 128)>>8>255 ? 255 : (298*C1 + 409*E1 + 128)>>8);
                    G1 = ((298*C1 - 100*D1 - 208*E1 + 128)>>8>255 ? 255 : (298*C1 - 100*D1 - 208*E1 + 128)>>8);
                    B1 = ((298*C1+516*D1 +128)>>8>255 ? 255 : (298*C1+516*D1 +128)>>8);
                    R2 = ((298*C2 + 409*E1 + 128)>>8>255 ? 255 : (298*C2 + 409*E1 + 128)>>8);
                    G2 = ((298*C2 - 100*D1 - 208*E1 + 128)>>8>255 ? 255 : (298*C2 - 100*D1 - 208*E1 + 128)>>8);
                    B2 = ((298*C2 + 516*D1 +128)>>8>255 ? 255 : (298*C2 + 516*D1 +128)>>8);
                    *(pRGBData+(height-i-1)*width*4+j*8+2) = R1<0 ? 0 : R1;
                    *(pRGBData+(height-i-1)*width*4+j*8+1) = G1<0 ? 0 : G1;
                    *(pRGBData+(height-i-1)*width*4+j*8) = B1<0 ? 0 : B1;
                    *(pRGBData+(height-i-1)*width*4+j*8+3) = alpha;
                    *(pRGBData+(height-i-1)*width*4+j*8+6) = R2<0 ? 0 : R2;
                    *(pRGBData+(height-i-1)*width*4+j*8+5) = G2<0 ? 0 : G2;
                    *(pRGBData+(height-i-1)*width*4+j*8+4) = B2<0 ? 0 : B2;
                    *(pRGBData+(height-i-1)*width*4+j*8+7) = alpha;
                }
            }
        }
    }
    else
    {
        if (alphaYUV)
        {
            for (int i=0; i<height; ++i)
            {
                for (int j=0; j<width/2; ++j)
                {
                    Y1 = *(pYUVData+i*width*3+j*4);
                    U1 = *(pYUVData+i*width*3+j*4+1);
                    Y2 = *(pYUVData+i*width*3+j*4+2);
                    V1 = *(pYUVData+i*width*3+j*4+3);
                    C1 = Y1-16;
                    C2 = Y2-16;
                    D1 = U1-128;
                    E1 = V1-128;
                    R1 = ((298*C1 + 409*E1 + 128)>>8>255 ? 255 : (298*C1 + 409*E1 + 128)>>8);
                    G1 = ((298*C1 - 100*D1 - 208*E1 + 128)>>8>255 ? 255 : (298*C1 - 100*D1 - 208*E1 + 128)>>8);
                    B1 = ((298*C1+516*D1 +128)>>8>255 ? 255 : (298*C1+516*D1 +128)>>8);
                    R2 = ((298*C2 + 409*E1 + 128)>>8>255 ? 255 : (298*C2 + 409*E1 + 128)>>8);
                    G2 = ((298*C2 - 100*D1 - 208*E1 + 128)>>8>255 ? 255 : (298*C2 - 100*D1 - 208*E1 + 128)>>8);
                    B2 = ((298*C2 + 516*D1 +128)>>8>255 ? 255 : (298*C2 + 516*D1 +128)>>8);
                    *(pRGBData+(height-i-1)*width*3+j*6+2) = R1<0 ? 0 : R1;
                    *(pRGBData+(height-i-1)*width*3+j*6+1) = G1<0 ? 0 : G1;
                    *(pRGBData+(height-i-1)*width*3+j*6) = B1<0 ? 0 : B1;
                    *(pRGBData+(height-i-1)*width*3+j*6+5) = R2<0 ? 0 : R2;
                    *(pRGBData+(height-i-1)*width*3+j*6+4) = G2<0 ? 0 : G2;
                    *(pRGBData+(height-i-1)*width*3+j*6+3) = B2<0 ? 0 : B2;
                }
            }
        }
        else
        {
            for (int i=0; i<height; ++i)
            {
                for (int j=0; j<width/2; ++j)
                {
                    Y1 = *(pYUVData+i*width*2+j*4);
                    U1 = *(pYUVData+i*width*2+j*4+1);
                    Y2 = *(pYUVData+i*width*2+j*4+2);
                    V1 = *(pYUVData+i*width*2+j*4+3);
                    C1 = Y1-16;
                    C2 = Y2-16;
                    D1 = U1-128;
                    E1 = V1-128;
                    R1 = ((298*C1 + 409*E1 + 128)>>8>255 ? 255 : (298*C1 + 409*E1 + 128)>>8);
                    G1 = ((298*C1 - 100*D1 - 208*E1 + 128)>>8>255 ? 255 : (298*C1 - 100*D1 - 208*E1 + 128)>>8);
                    B1 = ((298*C1+516*D1 +128)>>8>255 ? 255 : (298*C1+516*D1 +128)>>8);
                    R2 = ((298*C2 + 409*E1 + 128)>>8>255 ? 255 : (298*C2 + 409*E1 + 128)>>8);
                    G2 = ((298*C2 - 100*D1 - 208*E1 + 128)>>8>255 ? 255 : (298*C2 - 100*D1 - 208*E1 + 128)>>8);
                    B2 = ((298*C2 + 516*D1 +128)>>8>255 ? 255 : (298*C2 + 516*D1 +128)>>8);
                    *(pRGBData+(height-i-1)*width*3+j*6+2) = R1<0 ? 0 : R1;
                    *(pRGBData+(height-i-1)*width*3+j*6+1) = G1<0 ? 0 : G1;
                    *(pRGBData+(height-i-1)*width*3+j*6) = B1<0 ? 0 : B1;
                    *(pRGBData+(height-i-1)*width*3+j*6+5) = R2<0 ? 0 : R2;
                    *(pRGBData+(height-i-1)*width*3+j*6+4) = G2<0 ? 0 : G2;
                    *(pRGBData+(height-i-1)*width*3+j*6+3) = B2<0 ? 0 : B2;
                }
            }
        }
    }
    return 0;
}

//////////////////////////////////////////////////////////////////////////
// RGB2YUV
// pRGB         point to the RGB data
// pYUV         point to the YUV data
// width        width of the picture
// height       height of the picture
// alphaYUV     is there an alpha channel in YUV
// alphaRGB     is there an alpha channel in RGB
//////////////////////////////////////////////////////////////////////////
int RGB2YUV(void* pRGB, void* pYUV, int width, int height, bool alphaYUV, bool alphaRGB)
{
    if (NULL == pRGB)
    {
        return -1;
    }
    unsigned char* pRGBData = (unsigned char *)pRGB;
    unsigned char* pYUVData = (unsigned char *)pYUV;
    if (NULL == pYUVData)
    {
        if (alphaYUV)
        {
            pYUVData = new unsigned char[width*height*3];
        }
        else
            pYUVData = new unsigned char[width*height*2];
    }
    int R1, G1, B1, R2, G2, B2, Y1, U1, Y2, V1;
    int alpha1, alpha2;
    if (alphaYUV)
    {
        if (alphaRGB)
        {
            for (int i=0; i<height; ++i)
            {
                for (int j=0; j<width/2; ++j)
                {
                    B1 = *(pRGBData+(height-i-1)*width*4+j*8);
                    G1 = *(pRGBData+(height-i-1)*width*4+j*8+1);
                    R1 = *(pRGBData+(height-i-1)*width*4+j*8+2);
                    alpha1 = *(pRGBData+(height-i-1)*width*4+j*8+3);
                    B2 = *(pRGBData+(height-i-1)*width*4+j*8+4);
                    G2 = *(pRGBData+(height-i-1)*width*4+j*8+5);
                    R2 = *(pRGBData+(height-i-1)*width*4+j*8+6);
                    alpha2 = *(pRGBData+(height-i-1)*width*4+j*8+7);
                    Y1 = (((66*R1+129*G1+25*B1+128)>>8) + 16) > 255 ? 255 : (((66*R1+129*G1+25*B1+128)>>8) + 16);
                    U1 = ((((-38*R1-74*G1+112*B1+128)>>8)+((-38*R2-74*G2+112*B2+128)>>8))/2 + 128)>255 ? 255 : ((((-38*R1-74*G1+112*B1+128)>>8)+((-38*R2-74*G2+112*B2+128)>>8))/2 + 128);
                    Y2 = (((66*R2+129*G2+25*B2+128)>>8) + 16)>255 ? 255 : ((66*R2+129*G2+25*B2+128)>>8) + 16;
                    V1 = ((((112*R1-94*G1-18*B1+128)>>8) + ((112*R2-94*G2-18*B2+128)>>8))/2 + 128)>255 ? 255 : ((((112*R1-94*G1-18*B1+128)>>8) + ((112*R2-94*G2-18*B2+128)>>8))/2 + 128);
                    *(pYUVData+i*width*3+j*6) = Y1;
                    *(pYUVData+i*width*3+j*6+1) = U1;
                    *(pYUVData+i*width*3+j*6+2) = Y2;
                    *(pYUVData+i*width*3+j*6+3) = V1;
                    *(pYUVData+i*width*3+j*6+4) = alpha1;
                    *(pYUVData+i*width*3+j*6+5) = alpha2;
                }
            }
        }
        else
        {
            unsigned char alpha = 255;
            for (int i=0; i<height; ++i)
            {
                for (int j=0; j<width/2; ++j)
                {
                    B1 = *(pRGBData+(height-i-1)*width*3+j*6);
                    G1 = *(pRGBData+(height-i-1)*width*3+j*6+1);
                    R1 = *(pRGBData+(height-i-1)*width*3+j*6+2);
                    B2 = *(pRGBData+(height-i-1)*width*3+j*6+3);
                    G2 = *(pRGBData+(height-i-1)*width*3+j*6+4);
                    R2 = *(pRGBData+(height-i-1)*width*3+j*6+5);
                    Y1 = ((66*R1+129*G1+25*B1+128)>>8) + 16;
                    U1 = ((-38*R1-74*G1+112*B1+128)>>8+(-38*R2-74*G2+112*B2+128)>>8)/2 + 128;
                    Y2 = ((66*R2+129*G2+25*B2+128)>>8) + 16;
                    V1 = ((112*R1-94*G1-18*B1+128)>>8 + (112*R2-94*G2-18*B2+128)>>8)/2 + 128;
                    Y1 = (((66*R1+129*G1+25*B1+128)>>8) + 16) > 255 ? 255 : (((66*R1+129*G1+25*B1+128)>>8) + 16);
                    U1 = ((((-38*R1-74*G1+112*B1+128)>>8)+((-38*R2-74*G2+112*B2+128)>>8))/2 + 128)>255 ? 255 : ((((-38*R1-74*G1+112*B1+128)>>8)+((-38*R2-74*G2+112*B2+128)>>8))/2 + 128);
                    Y2 = (((66*R2+129*G2+25*B2+128)>>8) + 16)>255 ? 255 : ((66*R2+129*G2+25*B2+128)>>8) + 16;
                    V1 = ((((112*R1-94*G1-18*B1+128)>>8) + ((112*R2-94*G2-18*B2+128)>>8))/2 + 128)>255 ? 255 : ((((112*R1-94*G1-18*B1+128)>>8) + ((112*R2-94*G2-18*B2+128)>>8))/2 + 128);
                    *(pYUVData+i*width*3+j*6) = Y1;
                    *(pYUVData+i*width*3+j*6+1) = U1;
                    *(pYUVData+i*width*3+j*6+2) = Y2;
                    *(pYUVData+i*width*3+j*6+3) = V1;
                    *(pYUVData+i*width*3+j*6+4) = alpha;
                    *(pYUVData+i*width*3+j*6+5) = alpha;
                }
            }
        }
    }
    else
    {
        if (alphaRGB)
        {
            for (int i=0; i<height; ++i)
            {
                for (int j=0; j<width/2; ++j)
                {
                    B1 = *(pRGBData+(height-i-1)*width*4+j*8);
                    G1 = *(pRGBData+(height-i-1)*width*4+j*8+1);
                    R1 = *(pRGBData+(height-i-1)*width*4+j*8+2);
                    B2 = *(pRGBData+(height-i-1)*width*4+j*8+4);
                    G2 = *(pRGBData+(height-i-1)*width*4+j*8+5);
                    R2 = *(pRGBData+(height-i-1)*width*4+j*8+6);
                    Y1 = (((66*R1+129*G1+25*B1+128)>>8) + 16) > 255 ? 255 : (((66*R1+129*G1+25*B1+128)>>8) + 16);
                    U1 = ((((-38*R1-74*G1+112*B1+128)>>8)+((-38*R2-74*G2+112*B2+128)>>8))/2 + 128)>255 ? 255 : ((((-38*R1-74*G1+112*B1+128)>>8)+((-38*R2-74*G2+112*B2+128)>>8))/2 + 128);
                    Y2 = (((66*R2+129*G2+25*B2+128)>>8) + 16)>255 ? 255 : ((66*R2+129*G2+25*B2+128)>>8) + 16;
                    V1 = ((((112*R1-94*G1-18*B1+128)>>8) + ((112*R2-94*G2-18*B2+128)>>8))/2 + 128)>255 ? 255 : ((((112*R1-94*G1-18*B1+128)>>8) + ((112*R2-94*G2-18*B2+128)>>8))/2 + 128);
                    *(pYUVData+i*width*2+j*4) = Y1;
                    *(pYUVData+i*width*2+j*4+1) = U1;
                    *(pYUVData+i*width*2+j*4+2) = Y2;
                    *(pYUVData+i*width*2+j*4+3) = V1;
                }
            }
        }
        else
        {
            for (int i=0; i<height; ++i)
            {
                for (int j=0; j<width/2; ++j)
                {
                    B1 = *(pRGBData+(height-i-1)*width*3+j*6);
                    G1 = *(pRGBData+(height-i-1)*width*3+j*6+1);
                    R1 = *(pRGBData+(height-i-1)*width*3+j*6+2);
                    B2 = *(pRGBData+(height-i-1)*width*3+j*6+3);
                    G2 = *(pRGBData+(height-i-1)*width*3+j*6+4);
                    R2 = *(pRGBData+(height-i-1)*width*3+j*6+5);
                    Y1 = (((66*R1+129*G1+25*B1+128)>>8) + 16) > 255 ? 255 : (((66*R1+129*G1+25*B1+128)>>8) + 16);
                    U1 = ((((-38*R1-74*G1+112*B1+128)>>8)+((-38*R2-74*G2+112*B2+128)>>8))/2 + 128)>255 ? 255 : ((((-38*R1-74*G1+112*B1+128)>>8)+((-38*R2-74*G2+112*B2+128)>>8))/2 + 128);
                    Y2 = (((66*R2+129*G2+25*B2+128)>>8) + 16)>255 ? 255 : ((66*R2+129*G2+25*B2+128)>>8) + 16;
                    V1 = ((((112*R1-94*G1-18*B1+128)>>8) + ((112*R2-94*G2-18*B2+128)>>8))/2 + 128)>255 ? 255 : ((((112*R1-94*G1-18*B1+128)>>8) + ((112*R2-94*G2-18*B2+128)>>8))/2 + 128);
                    *(pYUVData+i*width*2+j*4) = Y1;
                    *(pYUVData+i*width*2+j*4+1) = U1;
                    *(pYUVData+i*width*2+j*4+2) = Y2;
                    *(pYUVData+i*width*2+j*4+3) = V1;
                }
            }
        }
    }
    return 0;
}

//////////////////////////////////////////////////////////////////////////
// pGBYUV           point to the background YUV data
// pFGYUV           point to the foreground YUV data
// width            width of the picture
// height           height of the picture
// alphaBG          is there an alpha channel in background YUV data
// alphaFG          is there an alpha channel in fourground YUV data
//////////////////////////////////////////////////////////////////////////
int YUVBlending(void* pBGYUV, void* pFGYUV, int width, int height, bool alphaBG, bool alphaFG)
{
    if (NULL == pBGYUV || NULL == pFGYUV)
    {
        return -1;
    }
    unsigned char* pBGData = (unsigned char*)pBGYUV;
    unsigned char* pFGData = (unsigned char*)pFGYUV;
    if (!alphaFG)
    {
        if (!alphaBG)
        {
            memcpy(pBGData, pFGData, width*height*2);
        }
        else
        {
            for (int i=0; i<height; ++i)
            {
                for (int j=0; j<width/2; ++j)
                {
                    *(pBGData+i*width*2+j*4) = *(pFGData+i*width*2+j*4);
                    *(pBGData+i*width*2+j*4+1) = *(pFGData+i*width*2+j*4+1);
                    *(pBGData+i*width*2+j*4+2) = *(pFGData+i*width*2+j*4+2);
                    *(pBGData+i*width*2+j*4+3) = *(pFGData+i*width*2+j*4+3);
                }
            }
        }
    }
    int Y11, U11, V11, Y12, Y21, U21, V21, Y22;
    int alpha1, alpha2;
    if (!alphaBG)
    {
        for (int i=0; i<height; ++i)
        {
            for (int j=0; j<width/2; ++j)
            {
                Y11 = *(pBGData+i*width*2+j*4);
                U11 = *(pBGData+i*width*2+j*4+1);
                Y12 = *(pBGData+i*width*2+j*4+2);
                V11 = *(pBGData+i*width*2+j*4+3);

                Y21 = *(pFGData+i*width*3+j*6);
                U21 = *(pFGData+i*width*3+j*6+1);
                Y22 = *(pFGData+i*width*3+j*6+2);
                V21 = *(pFGData+i*width*3+j*6+3);
                alpha1 = *(pFGData+i*width*3+j*6+4);
                alpha2 = *(pFGData+i*width*3+j*6+5);

                *(pBGData+i*width*2+j*4) = (Y21-16)*alpha1/255+(Y11-16)*(255-alpha1)/255+16;
                *(pBGData+i*width*2+j*4+1) = ((U21-128)*alpha1/255+(U11-128)*(255-alpha1)/255 + (U21-128)*alpha2/255+(U11-128)*(255-alpha2)/255)/2+128;
                *(pBGData+i*width*2+j*4+3) = ((V21-128)*alpha1/255+(V11-128)*(255-alpha1)/255 + (V21-128)*alpha2/255+(V11-128)*(255-alpha2)/255)/2+128;
                *(pBGData+i*width*2+j*4+2) = (Y22-16)*alpha2/255+(Y12-16)*(255-alpha2)/255+16;
            }
        }
    }
    else
    {
        for (int i=0; i<height; ++i)
        {
            for (int j=0; j<width/2; ++j)
            {
                Y11 = *(pBGData+i*width*3+j*6);
                U11 = *(pBGData+i*width*3+j*6+1);
                Y12 = *(pBGData+i*width*3+j*6+2);
                V11 = *(pBGData+i*width*3+j*6+3);

                Y21 = *(pFGData+i*width*3+j*6);
                U21 = *(pFGData+i*width*3+j*6+1);
                Y22 = *(pFGData+i*width*3+j*6+2);
                V21 = *(pFGData+i*width*3+j*6+3);
                alpha1 = *(pFGData+i*width*3+j*6+4);
                alpha2 = *(pFGData+i*width*3+j*6+5);

                *(pBGData+i*width*3+j*6) = (Y21-16)*alpha1/255+(Y11-16)*(255-alpha1)/255+16;
                *(pBGData+i*width*3+j*6+1) = ((U21-128)*alpha1/255+(U11-128)*(255-alpha1)/255 + (U21-128)*alpha2/255+(U11-128)*(255-alpha2)/255)/2+128;
                *(pBGData+i*width*3+j*6+3) = ((V21-128)*alpha1/255+(V11-128)*(255-alpha1)/255 + (V21-128)*alpha2/255+(V11-128)*(255-alpha2)/255)/2+128;
                *(pBGData+i*width*3+j*6+2) = (Y22-16)*alpha2/255+(Y12-16)*(255-alpha2)/255+16;
            }
        }
    }
    return 0;
}

经测试，功能已经实现，如有错误或者不妥的地方，恳请指出。
mosesyuan at gmail dot com