Help for SAMPLER

PURPOSE

 Performs sampling on input images and creates an output ibis file. If
 sampletype is stratified then a ngridx X ngridy grid is placed over
 the image and a sample is randomly chosen from each of the grid cells.

 The output ibis file contains two more columns than the number of
 input files. The first two columns of the output ibis file contain
 respectively the zero-based grid line and sample numbers of the
 samples. The remaining columns contain the samples for each of the
 input images.

 The output ibis file from sampler typically is consumed by the
 clusterer program.

 ORIGINAL PROGRAMMER:   P. Kim  16 Sep 2011

 REVISIONS:
  2016-10-20 WLB - Migrated to MIPL, enhanced test case and documentation.
  2017-08-11 WLB - Removed DEBUG from imake.
  2019-09-06 WLB - IDS-7922 - Initialized some variables; cleaned up -Wall warnings.