GEOTIFF_READ: read geotiff using imread and assign map info from infinfo.

I = GEOTIFF_READ('filename');
Reads whole images
I = GEOTIFF_READ('filename','pixel_subset', [minx maxx miny maxy]);
I = GEOTIFF_READ('filename','map_subset' , [minx maxx miny maxy]);
extract subset of the specified.

% output:
I.z, image data
I.x, x coordinate in map
I.y, y coordinate in map
I.info, misc. info

imshow(I.z, 'xdata', I.x, 'ydata', I.y);
shows image with map coordinate

% Version by Yushin Ahn
% Glacier Dynamics Laboratory,
% Byrd Polar Resear Center, Ohio State University
% Referenced enviread.m (Ian Howat)