This is from the README.MinGW. I'm pretty sure these are the ones I have
and they work...
libtiff, libjpeg, and zlib
Needed for image handling support in the GNUstep gui libary
(not required for GNUstep-base, though zlib can be used by the base
library).
Get the binary packages from -
http://prdownloads.sourceforge.net/gnuwin32/tiff-3.5.7-lib.zip
http://prdownloads.sourceforge.net/gnuwin32/tiff-3.5.7-bin.zip
http://prdownloads.sourceforge.net/gnuwin32/libjpeg-6b-lib.zip
http://prdownloads.sourceforge.net/gnuwin32/libjpeg-6b-bin.zip
http://prdownloads.sourceforge.net/gnuwin32/zlib-1.1.4-lib.zip
http://prdownloads.sourceforge.net/gnuwin32/zlib-1.1.4-bin.zip