This directory contains the source for the program mergescan, written 
April 2011 on Expedition 335 to merge 4 outer-core tiff images from the SHIL
to a single simulated unrolled 360-degree image.  This was developed and
tested on a MacBook Pro (OS 10.6.7; gcc version 4.2.1), but should work on any
unix or unix-like system that can support tifflib.

Compilation:  If gcc, zlib, and tifflib are all installed, compilation should
be a simple matter of typing 'make mergescan' in this directory.  I found 
tifflib (v3.9.5) installation to be straightforward once I realized zlib was
already installed.

Usage:  For the sake of easy development, the program only runs in command-line
mode, for example in the Mac Terminal utility.  The basic usage is

mergescan file1.tif file2.tif file3.tif file4.tif

where file*.tif are SHIL files of the same core listed in clockwise-downcore
order.  Output is by default written to the file mergeout.tif in the
working directory, which if successful will need to be renamed to something
meaningful that won't be overwritten by the next run of the program.

Options:  There are three options so far, one for the core diameter, one
for the decimation factor for file size reduction, and one for the output
filename.  The core diameter defaults to 58.0 mm and the decimation factor
defaults to 4 (reducing 20 pixels per mm to 5 per mm).  Option syntax is

mergescan f1.tif f2.tif f3.tif f4.tif diameter=55.5 decimate=2 out=myfile.tif

with option(s) coming after filenames and no spaces around the equal sign.
The program has no trouble writing at decimate=1, but having another 
application read the file can be a problem.


Details:  The program assumes cores are perfect cylinders and fills the
unrolled image one scan line at a time by stepping uniformly through
destination pixels on the circumference, using simple trigonometry to find
the appropriate source pixel in the images.  If not decimated, some source 
pixels will be duplicated away from each source image center to achieve the 
appropriate stretching.  Several properties of the source images, such as
resolution, image width, and header length, are compiled into the program.
There's no reason the program can't be modified to read jpegs instead of
tiffs, but I find tifflib much better documented than any jpeg library
I've looked at.  Due to very poor recovery on Exp 335, the program has 
only been applied to two real cores.

-------
Doug Wilson,  May 2011