[Insight-developers] fast image pixel access method

[Bradley Lowekamp]

Hello,

On May 13, 2013, at 11:03 AM, "Gao, Yi" <gaoyi.cn at gmail.com> wrote:
> When using NeighborhoodIterator, i'm not sure if the boundary checking is automatically turned on. I guess if that is by default on, then there is not much speed gain with it.


Because the region you specify to the Iterator is on the boundary it will turn on the boundary checking. You can either turn off the condition:

http://www.itk.org/Doxygen/html/classitk_1_1ConstNeighborhoodIterator.html#a438cb0146b802b04a771a2461952cff8

or you can change the region size you initialize the Iterator with.

You can just use the operator<< to check what the iterator is doing.

Also consider using a large type for the accumulation type, such as itk::NumericTraits<T>::AccumulatorType;

And consider using std::accumulate(it.Begin(), it.End(), 0 )

Brad