Infill/Fill with surrounding color

[a-lobsterman]

[attachment=6929]Working with a TIFF file of aerial orthoimagery from the State of Maine. Because the passes I'm using were only for land-forms (tide levels) portions of the imagery were omitted. The attachment shows a white space in the aerial runs which I would like to try to fill to more or less match the surrounding color/patters. Been struggling with the Fill with Pattern but perhaps this is not the right tool? Pointers to examples or tutorials very welcome.