RGB565图像转灰度图像
各位大侠，我写了个RGB565转灰度图像的算法，但是转换后的灰度图像过暗，不知道是怎么回事，求帮助啊...

#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;
}
}
}

565图像
[img=http://my.csdn.net/yhterry/album/detail/1178890][/img]
灰度图像
[img=http://my.csdn.net/yhterry/album/detail/1178891][/img]
[解决办法]
unsigned char chR = ((*(pData565 + iIndex) & RGB565_MASK_RED) >> 11 ) << 3;
unsigned char chG = ((*(pData565 + iIndex) & RGB565_MASK_GREEN) >> 5) << 2;
unsigned char chB = (*(pData565 + iIndex) & RGB565_MASK_BLUE) << 3 ;

>> 的优先级比 & 高， 再加括号的说...