EXPORT_OVERLAY(FILENAME, OUTPUT, RECT)

SYNTAX:
export_overlay(filename, output, [N, S, E, W])
export_overlay(filename, output, [N, S, E, W, R])

INPUT:
filename: must be either:
1. Google Earth supported image file (see below), OR
2. MATLAB format .fig file, OR
3. a figure object handle (use gcf for current figure)

output: .kmz file name (string, relative or full path)

rect: 4 or 5-element vector in the following format:
[north boundary, south bound, east bound, west bound, rotation]

NOTE: If you specify a figure handle or .fig file, it will be exported
as a TRANSPARENT .png file.

GOOGLE EARTH SUPPORTED FORMATS:
.bmp, .dds, .gif, .jpg, .pgm, .png, .ppm, .tga, .tiff, .tif

EXAMPLE 1:
% this will place an overlay of a random plot over Hawaii.
plot(1:1:10, rand(10,1), 'w');
rect = [21.37, 21.36, -157.971, -157.973];
export_overlay(gcf, 'output.kmz', rect);

EXAMPLE 2:
% this will overlay a PNG image over the same location.
% (Assuming 'contour.png' is defined)
rect = [21.37, 21.36, -157.971, -157.973];
export_overlay('contour.png', 'contour.kmz', rect);

EXAMPLE 3:
% you may also use full or relative paths to various images you would
% like to overlay.
rect = [21.37, 21.36, -157.971, -157.973];
file1 = '/home/user/Desktop/contour.png';
file2 = 'figfiles/myfig.fig';
export_overlay(file1, 'contour.kmz', rect);
export_overlay(file2, 'myfig.kmz', rect);