sharpen gif ??

[Christian Wenz]

i scaned a coulor picture with gimp and saved it in a gif-format. after
that i load it in xfig to add some arrows and such stuff and write it as
an eps-file. now i see that the edges of the picture are not so sharp as
i expect. if i save the same one as postscript and after work with xfig
as eps i get more sharp edges but a huge file. is there a way to improve
the quality of gif with gimp or is it more a problem of the gif-format
itself ???