The libfprint ebuild contains a dependency on x11-libs/gtk+:2 but it actually builds fine without it installed. Reproducible: Always Looking at the configure script it looks like it could use gdk-pixbuff instead of imagemagick, maybe that's where the confusion came from?
Also, DEPEND="${DEPEND} <-- fail
+ 13 Feb 2012; Michael Weber <xmw@gentoo.org> libfprint-0.4.0.ebuild: + Drop x11-libs/gtk+:2 dependency. Thanks Andrei Slavoiu (bug 403189) for + clarification. +
Thanks for pointing that out! @@ -16,12 +16,10 @@ KEYWORDS="~amd64 ~x86" IUSE="debug static-libs" -RDEPEND="dev-libs/glib:2 - dev-libs/libusb:1 +RDEPEND="dev-libs/libusb:1 dev-libs/nss - x11-libs/gtk+:2 - || ( media-gfx/imagemagick media-gfx/graphicsmagick[imagemagick] )" -DEPEND="${DEPEND} + || ( media-gfx/imagemagick media-gfx/graphicsmagick[imagemagick] x11-libs/gdk-pixbuf )" +DEPEND="${RDEPEND} dev-util/pkgconfig" S=${WORKDIR}/${MY_PV}