This is an amended version of simple_take.c.

The files below are all in the directory /opt/EDTpdv/hartmann/src

1. simple_hartmann.c   - the C code to access the frame grabber, retrieve an image, load the MATLAB engine and pass the image to MATLAB for centroiding
2. centroid_image.m  - the MATLAB routine that centroids the image
3. get_defocus.m - the MATLAB function that determines the defocus in the centroids
4. build_simple_hartmann.sh - a shell script I wrote that contains the compile and link options to build the thing correctly 

/**
 * @file
 * An example program to show usage of EDT PCI DV library to acquire and
 * optionally save single or multiple images from devices connected to EDT
 * high speed digital video interface such as the PCI DV C-Link or PCI DV
 * FOX / RCX.
 * 
 * Provided as a starting point example for adding digital video acquisition
 * to a user application.  Includes optimization strategies that take
 * advantage of the EDT ring buffer library subroutines for pipelining image

function defocus = get_defocus(centroids)
% 
% a function to extract the defocus of the gradient field
%
% 'centroids' structure
% --------------------
% centroids.image_background_level  - the background intensity of an image
%                                     with no illumination on it
%          .spot_radius             - the radius of a hartmann spot
%          .spot_threshold_level    - the minimum intensity of pixels used to