image variable attributes

These attributes provide additional information about the state and type of the image data contained in the MINC 2.0 file.

1. complete - A boolean attribute (with values ``true_'' or ``false'') that indicates whether the variable has been written in its entirety. This can be used to detect program failure when writing out images as they are processed : complete is set to false at the beginning and set to true_ when all data has been processed and written to the file.

2. valid_range - A vector of two numbers which specifies both the minimum and maximum valid values for this variable. Values outside this range must be treated as missing or uninitialized. In MINC, the order of the two values in the vector is not significant.

   This attribute should be considered mandatory for the MINC image variable, unless the variable uses the default range, which is defined to be the full range of an (possibly signed or unsigned) integer type or the interval (0.0, 1.0) for floating point types. It is not required for any other MINC variable.