The [n] and [x] parts of the name are optional. If used [n] indicates the number of dimensions of the data (1 to 3, the default is 2) and [x] the data type (one of R, D, I, W, UW, B or UB, the default is R). So for instance if you wanted to use 3-D data with a data type of INTEGER, the subroutine that you should call is IMG_NEW3I.
IMG Simple Image Data Access