输入为积分图，输出为均值
inline void pbgBoxFilter(zfloat_t* aver, const uint32_t *pSum, zfloat_t c, int32_t sumStride,
int32_t rdStride, int32_t ldStride, int32_t ruStride, int32_t luStride)
{
int32_t blkWidth = BLK_DOWN_SIZE;
const uint32_t* pSumRow = pSum;
int32_t idx = 0;
for (int32_t h = 0; h < blkWidth; h++)
{
uint32_t winSum = 0;
for (int32_t w = 0; w < blkWidth; w++)
{
winSum = pSumRow[rdStride + w] - pSumRow[ruStride + w]
- pSumRow[ldStride + w] + pSumRow[luStride + w];
aver[idx] = winSum * c;
idx ++;
}
pSumRow += sumStride;
}
}