IAVG(1)
======
:doctype: manpage

Name
----
iavg - Image combiner

Synopsis
--------
*iavg* [options] imagefile1 imagefile2 ...

Description
-----------

In default mode, *iavg* calculates an average of a stack of images.

Options
-------

**-b__n__**:: Set black level to _n_ + 2.

**-e**:: Fill black area near top edge with first nonblack
   pixel. (This is mainly a hack for a specific application.)

**-h**:: Calculate ``HV'' histograms.

**-m**:: Enable use of x-ramps. (This is a hack for a specific
   application.)

**-q**:: Quiet (may be repeated to suppress yet more verbosity).

**-r**:: Invert black/white in input images.

**-w__n__**:: Set white level to _n_ + 2.

Other options select modes as in the following table:

|======================================================================
| *Option* | *Mode*
|   -0 or -a   | Average of images with contrast rescaling (``adaptive'')
|           -1   | Range (maximum - minimum) of images           
|           -2   | Minimum of images                             
|           -3   | Minimum of images                             
|           -4   | Average of horizontal contrast image
|   -5 or -s   | Stack (output raw image data without headers) 
|   -6 or -i   | Stack of cumulative sums in z (no headers)    
|   -7   or -p   | Average only of non-black pixels
|   -+           | Add all images together
|   -&#45;           | Subtract sum of secondary images from first image
|======================================================================

Of these, **-p** (only) takes an optional argument that specifies the
minimum number of images to consider. (Default is 4; if fewer are
nonblack, the output value is 150.)

If no mode is specified, the default is simply averaging all pixel values.

Output is always written to stdout as a pgm image.

Notes
-----
In mode 7, an additional image file called ``pixcnt.pgm'' is created that
holds the counts of nonblack pixels.

If histograms are enabled, a (normalized) histogram image is created
that is 256 x (W+H) pixels large and contains the gray-value
histograms taken over rows and columns of the source images. This
image is saved as ``xy_hists.pgm''.

Authors
-------
*iavg* was written by Tom Wetzel. This page was written by Daniel
 Wagenaar.
