RGB565图像转灰度图像解决办法

#define RGB565_MASK_RED        0xF800   
#define RGB565_MASK_GREEN      0x07E0   
#define RGB565_MASK_BLUE       0x001F   


void Convert(unsigned char *img565, unsigned char *imgGray, int iWidth, int iHeight)
{
    WORD *pData565 = (WORD*)img565;
    int iIndex = 0;
    for (int x = 0; x < iHeight; ++x)
    {
        for (int y = 0; y < iWidth; ++y)
        {
            unsigned char chR = *(pData565 + iIndex) & RGB565_MASK_RED >> 11;
            unsigned char chG = *(pData565 + iIndex) & RGB565_MASK_GREEN >> 5;
            unsigned char chB = *(pData565 + iIndex) & RGB565_MASK_BLUE;
//            unsigned char chGray = (chB*11 +chR*30 +chG*59+50)/100;
            unsigned char chGray = (chB*0.3 +chR*0.11 +chG*0.59);
//            unsigned char chGray = (chR + chG + chB) / 3.0;
//            unsigned char chGray = (chB*29 +chR*77 +chG*150+128)/256;
//            unsigned char chGray = (chB/31.0*0.3 +chR/31.0*0.11 +chG/63.0*0.59)*255;
            *(imgGray + x * iWidth + y) = chGray;
            ++iIndex;
        }
    }
}