New programs for stack filter design
-------------------------------------

coeff_v2
  Computation of cost coefficients
  Same algorithm as previous coeff, with the following enhancements:
  - allows multiple noisy files (corrupting the same desired image),
    numbered "_00", "_01" etc.
  - MERGE_SORT is a compilation option which activates merge sort.
    If not active, insertion sort is used.
    Merge sort is better for window size > 12, but this may depend
    on the machine, compiler etc.
  - costs are saved as integers.
  - two bugs fixed.
  Compile with:
    cc coeff_v2.c -o coeff_v2.out -lm
  Run with:
    coeff_v2.out desired_image noisy_image costs_file


fast_v2
  Design of a stack filter starting from costs.
  Uses the algorithm of the previous program "fast", with the
  following modifications:
  (Referred as FASTAR* in tec_report.ps)
  - the gain of changing the value of an undecided node is
  computed with a recursive procedure.
  - the costs are read as integers.
  Compilation options:
    REC_COMP_COST - activate recursive gains computation
		    (should be always on)
  Compile with:
    cc fast_v2.c -o fast_v2.out -lm
  Run with:
    fast_v2.out costs_file filter_file


fast_v3
  Design of a stack filter starting from costs.
  A new algorithm using a very fast suboptimal heuristic,
  whose description may be found in tec_report.ps.
  Same I/O as fast_v2.
  Compilation options:
    REC_COMP_COST - activate recursive gains computation
		    (should be always on)
    COMBINE_SONS  - activate the second improvement step,
		    which may have low efficiency
		    (try it)
    RUN_LP	  - activate the linear programming routines
		    (should be disactivated for large windows
		    and is useful only for medium size windows)
  Compile with:
    cc fast_v3.c -o fast_v3.out -lm
  Run with:
    fast_v3.out costs_file filter_file


train_nsip97
  Design of a stack filter starting from costs.
  The algorithm of Fong, Adams, Coyle and Yoo presented
  at NSIP '97.
  Same I/O as fast_v2.
  Define:
    NUMBER_ITER	  - number of iterations. To be tuned function
		    of the window size, image, etc.
		    (This define was introduced since it is
		    very difficult to implement an automatic
		    stopping criterion.)
    DEC_THR	  - maximal value allowed to "soft decisions".
		    (It doesn't seem to make great difference
		    if sufficiently large, e.g. > 1000.)
  Compile with:
    cc train_nsip97.c -o train_nsip97.out -lm
  Run with:
    train_nsip97.out costs_file filter_file


filter_v2
  Filter a noisy image.
  Identical with previous filter program, with two bugs fixed.
  Compile with:
    cc filter_v2.c -o filter_v2.out -lm
  Run with:
    filter_v2.out desired_image noisy_image filter_file filtered_image