Help for CONCOMP1

 PURPOSE:

concomp1 is a VICAR applications program used to remove high frequency
information (noise) components from digital images.  It is usually used as a
post-processing procedure to remove visually distracting detail from classified
or stratified images such as images produced by VICAR programs FASTCLAS or
USTATS.  Such images usually are composed of a number of regions, where each
pixel in a region has the same DN except possibly for some isolated noise
pixels. CONCOMP1 changes the DNs of these isolated noise pixels to match the DN
of the surrounding pixels and writes the resulting image to an output file. 
A mask of changed pixels can be generated on request. 
 EXECUTION:

In order to determine which DNs to change, concomp1 applies a test to each
pixel in the input image.  The test involves looking at a 3 by 3 (pixel)
window centered around the pixel being tested.  The number of other pixels
in the window with the same DN as the pixel being tested is found.  If this
number is less than the threshold value specified by the THRESH parameter,
then the DN for the pixel being tested is changed.  The new value of the DN
is determined by the MODE or REPLACE parameters specified by the user.  If
REPLACE is specified, the new value is just the value specified for the REPLACE
parameter.  If MODE is specified, the new value is generally the mode of the DN
distribution within the window.  More precisely, if MODE is specified, the
new DN is the most frequent DN in the window that lies in the range of DNs
specified for the RANGE parameter.  In case of a tie in determining the 
most frequent DN, the lowest of the DNs in the tie is used.  If no DN in
the specified range occurs in the window, the DN of the pixel tested is not
changed.  The range is commonly set according to the range of DNs for the
regions of the image.  When a DN is changed, the change is not included in 
the subsequent windows. 

A mask file is specified by entering a second output file name for the OUT
parameter.  The mask file is the same size as the (first) output file.  A
pixel in the mask file has a DN of 0 if the DN for the corresponding pixel
in the output file was changed.  All other pixels in the mask file have a
DN of 255.   It is possible that the DN of a pixel in the image be change to
itself, particularly if the value of the THRESH parameter is greater than 3.
In this case, the corresponding pixel in the mask file will be 0.


TAE COMMAND LINE FORMAT
      The following command line formats show the major allowable forms:
      concomp1 INP=a OUT=b SIZE=(sl,ss,nl,ns) optional parameters
      concomp1 INP=a OUT=b  SL=sl SS=ss NL=nl NS=ns optional parameters
      concomp1 a b (sl,ss,nl,ns) optional parameters
      concomp1 a b optional parameters

      concomp1 INP=a OUT=(b,m) SIZE=(sl,ss,nl,ns) optional parameters
      concomp1 INP=a OUT=(b,m)  SL=sl SS=ss NL=nl NS=ns optional parameters
      concomp1 a (b,m) (sl,ss,nl,ns) optional parameters
      concomp1 a (b,m) optional parameters

       Here 'a' represents the input image file name, 
       'b' represents the output image file name,
       and 'm' represents the mask file name.
EXAMPLE

      concomp1 INP=A OUT=B THRESH=1 'MODE

      In this example the center pixel of the window will be changed unless it
      is connected to at least 1 other pixel with the same value.  The new
      value is found by taking the mode of the distribution of values in the
      window.


RESTRICTIONS
1. The input, output, and mask images must be byte data.
 OPERATION:

The operation of concomp1 is similar to the operation of a box-filtering
routine as it uses a moving window.  However, the pixel replacements are
based on a different decision rule.  concomp1 searches for and removes 
isolated pixels  and/or groups of pixels.  A 3 by 3 moving window is used
to find isolated pixels by comparing the central pixel of the window with
its adjacent pixels.  The number of other pixels in the window with the
same value is the 'connectivity factor'.  If the connectivity factor is
less than the THRESH parameter, the central pixel is replaced either by a 
user specified value or by the mode of the distribution within the window.

The window for pixels along the edges of the image is defined by conceptually
reflecting the image data about the edges.  Thus, the second line of the image
is conceptually duplicated above the first line, and the second pixel of each
line is conceptually duplicated to the left of the first pixel in a line.  The
next to last line of the image and the next to the last pixel in each line are
handled analogously.  This method compensates for the fact that edge pixels
have fewer real neighbors. 

The following window operations will demonstrate the operation of concomp1
on various windows.

Example 1:  specifying THRESH=1 and 'MODE

                    5   5   5                   5   5   5 

            INPUT:  3   2   5          OUTPUT:  3   5   5

                    4   3   3                   4   3   3

Example 2:  specifying THRESH=4

                    5   5   5

            INPUT:  3   2   2          OUTPUT:  no change

                    2   2   2 

Example 3:  specifying THRESH=6, 'MODE, and RANGE=(1,5)

                    0   0   0                   0   0   0

            INPUT:  0   0   0          OUTPUT:  0   2   0

                    2   2   1                   2   2   1


 WRITTEN BY:             Steve Pohorsky              14 Dec 1983

 COGNIZANT PROGRAMMER:   S. Z. Friedman              19 Dec 1980

 REVISIONS:
  1994-10-03 CRI - Made portable for UNIX
  2016-07-15 R. J. Bambery - Removed 2 GB maximum image size.
             by changing stacka call with stacka_big call
              Centos-7.2 & gcc-4.8.5
  2017-05-31 W. L. Bunch - Restored stacka

PARAMETERS: