These are the packages that would be merged, in order:

Calculating dependencies ... done!
Dependency resolution took 1.60 s (backtrack: 0/20).

[ebuild  N     ] media-libs/giflib-6.1.3:0/7::gentoo  USE="-doc -static-libs" 460 KiB
[ebuild   R    ] media-libs/tiff-4.7.1:0/6::gentoo  USE="cxx jpeg lzma* opengl zlib zstd* -jbig -lerc -libdeflate -static-libs -test -verify-sig -webp" 2304 KiB
[ebuild  N     ] media-libs/simage-1.8.5:0/20::gentoo  USE="gif jpeg png tiff zlib -qt6 -sndfile -test -vorbis" 6639 KiB
[ebuild  N     ] media-libs/coin-4.0.10::gentoo  USE="exceptions threads -debug -doc -openal -qch -test" 11578 KiB

Total: 4 packages (3 new, 1 reinstall), Size of downloads: 20979 KiB

The following USE changes are necessary to proceed:
 (see "package.use" in the portage(5) man page for more details)
# required by media-libs/simage-1.8.5::gentoo[tiff]
# required by media-libs/coin-4.0.10::gentoo
# required by =media-libs/coin-4.0.10 (argument)
>=media-libs/tiff-4.7.1 lzma zstd