IGCONV-Convolve an image with a specified filter

Description:

This Figaro function convolves an image with a box array that is defined in a text file as a set of numbers. This is more flexible - though less efficient - than the simple convolution performed by ICONV3.

Parameters:

IMAGE

The name of a 1- or 2-dimensional data file that is to be convoled with the data array defined in the file specified by the CONVOL parameter.

CONVOL

A text file (default extension .cvf) which contains the definition of the data array that the IMAGE data is to be convolved with. The convolution data often referred to as a filter, since one of the main uses of this routine is to apply sharpening or smoothing filters to images) is specified as a series of numbers in free format (blank lines and lines starting with '*' being ignored). Normally one line of the filter is specified by one line of the file, but a line can be continued by ending it with a 'character.

OUTPUT

The name of the resulting data file. This will be a copy of the input file, except that the main data array will have been convolved with the specified array.

Source comments:

 I G C O N V

 This is a general-purpose convolution program, able to convolve the
 main data array in a Figaro file with a rectangular array of any
 dimensions. This is a more flexible routine than ICONV3, where the
 convolution is with a 3x3 array specified only by a center and an
 edge value, but the additional flexibility probably makes it
 noticeably slower, particularly for very large convolution arrays.

 Command parameters -

 IMAGE    The name of the structure containing the image.

 CONVOL   This is the name of a text file that contains the
          definition of the convolution array. See below for the
          format.

 OUTPUT   The name of the result of the operation.  This can
          be the same as for IMAGE.  If not, a new structure
          is created, with everything but the data a direct
          copy of the input.

 File format:
    The text file defining the convolution array should simply contain
    the values for the array in a free format, one line at a time. Lines
    beginning with a '*' are ignored, as are blank lines. If the data for
    a line of the array has to be continued onto another line, a '\'
    should appear at the end of the line to be continued.

 11th Mar 1994.  Original version.  KS / AAO