1. readImageBW_8U

    MinimalImageB* img = new MinimalImageB(m.cols, m.rows);
    memcpy(img->data, m.data, m.rows*m.cols);
    return img;

2. Undistort::undistort
   主要调用
   photometricUndist->processFrame<T>(image_raw->data, exposure, factor);
   内部：
   float* data = output->image;
   for(int i=0; i<wh;i++)
   {
   data[i] = factor*image_in[i];
   }
   output->exposure_time = exposure_time;
   output->timestamp = 0;
   还有另一个分支
   data[i] = G[image_in[i]];
   反正就是要对 像素值 进行转换， 转为一种 浮点型数据

photometricUndist->output->copyMetaTo(*result);
other.exposure_time = exposure_time;

else
{
memcpy(result->image, photometricUndist->output->image, sizeof(float)wh);
}

至此，得到了ImageAndExposure* ret2