Toico converts PNG, GIF, TIFF, BMP (uncompressed) and XPM images to the Windows icon format (ICO). It is possible to create multi-resolution icon with full alpha channel.

Command line options:

toico [-vd] [-k RRGGBB] [-o icon] pic1 [pic2...]
toico [-h]
 -o  output to a file instead of stdout
 -d  force 1-bit transparency
 -k  transparency key for BMP files (usually magenta: FF00FF)
 -v  be verbose


Source: toico-1.1.tar.gz ()
Windows binary: toico.exe (154K)

Libraries (optional): libpng, libtiff, zlib.

Note: MIME type of ICO is image/