FILLFIGURE resets the position of an axes, and either its XLim or its YLlim, so that the axes completely fills its parent figure. After calling FILLFIGURE, you can make use of the entire figure window while zooming and panning an image.
The image used in the screen shot and first example, ngc6543a.jpg, is part of the standard MATLAB distribution. This image was created by the Space Telescope Science Institute, operated by the Association of Universities for Research in Astronomy, Inc., with support from NASA contract NAS5-26555, and is reproduced with permission from AURA/STScI. Digital renditions of images produced by AURA/STScI are obtainable royalty-free. Credits: J. P. Harrington and K. J. Borkowski (University of Maryland), and NASA.