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

Calculating dependencies ... done!
Dependency resolution took 1.05 s (backtrack: 0/20).

[ebuild  N     ] media-libs/giflib-6.1.3:0/7::gentoo  USE="-doc -static-libs" 460 KiB
[ebuild  N     ] media-libs/libexif-0.6.26::gentoo  USE="nls -doc -verify-sig" 1305 KiB
[ebuild  N     ] media-libs/libwebp-1.6.0:0/7::gentoo  USE="gif jpeg opengl png tiff -static-libs -swap-16bit-csp" CPU_FLAGS_X86="avx2 sse2 sse4_1" 4196 KiB
[ebuild  N     ] media-gfx/jp2a-1.3.2::gentoo  USE="-curl" 503 KiB

Total: 4 packages (4 new), Size of downloads: 6462 KiB