about mask_t

[gioipv]

Hello,
I see that, in mask_t. It is mask of t_f , It should be binary image. But when i calculate histogram of pixel value. ( from 0 to 255), There are some value between the value 0 and 255. (Ex: 12, 13, ...)
So that, can u tell me. U have been check there value. about the value, are there still correct. ?
I'm looking forward the answer from u