function GRABIT Extracts data points from an image file.
%
% GRABIT starts a GUI program for extracting data from an image file.
% It is capable of reading in BMP, JPG, TIF, GIF, and PNG files (anything
% that is readable by IMREAD). Multiple data sets can be extracted from a
% single image file, and the data is saved as an n-by-2 matrix variable in
% the workspace. It can also be renamed and saved as a MAT file.
%
% Following steps should be taken:
% 1. Load the image file.
% 2. Calibrate axes dimensions. You will be prompted to select 4 points
% on the image. Zoom and pan enabled.
% 3. Grab points by clicking on points. Right-click to delete a point.
% Image can be zoomed and panned.
% 4. Multiple data sets will remain in memory so long as the GUI is open.
% Variables can be renamed, saved to file, or edited in Array Editor.
%
% Panning is achieved by clicking and dragging on the image. Double-click
% to center view. Right click and drag to zoom in and out. In addition,
% there are keyboard shortcuts for zooming:
% <a> - zoom in
% <b> - zoom out
% <space> - reset view
%
% This code will also work for extracting data points from a tilted or a
% skewed image (even upside-down or mirrored). The calibration stage
% ensures that the imperfect orientation or quality of the image is
% accounted for.
%
% The types of files that will most likely work are BMP, JPG, TIF, GIF (up
% to 8-bit), and PNG files. Basically, any format supported by the IMREAD
% is accepted.
%
% GRABIT(FILENAME) will start the GUI program and open the image file
% FILENAME.
