The easiest way to get _lots_ of nifty spatial tools is to down load "FWTools: Open Source GIS Binary Kit for Windows and Linux"
GDAL includes useful command line tools for manipulating spatial data. And we can treat gigapans as spatial data.
Shrink a large image to 10% of its' original size:
gdal_translate -outsize 10% 10% infile.tif outfile.tif
RGBA Tiff images can be split into component parts. This is an interesting effect:
gdal_translate -b 1 -of JPEG -outsize 10% 10% maia_hands.tif m_b1.jpg
gdal_translate -b 2 -of JPEG -outsize 10% 10% maia_hands.tif m_b2.jpg
gdal_translate -b 3 -of JPEG -outsize 10% 10% maia_hands.tif m_b3.jpg
Merge two bands, with output greyscaled:
gdal_translate -b 1 -b 2 -outsize 10% 10% maia_hands.tif m_b12.tif
Crop an image
offset where the top left is 0,0.