I tried searching through my file explorer for location of the boot.img file but no luck other than through CWM. What I'd recommend is, if you have custom recovery, "backup current ROM" and then extract the boot.img from a file explorer to add to what you need to reflash the ROM. I believe the boot.img is made via the recovery backup and I wasn't able to find any by Google search.
Far into the unknown, the Galaxy is all you know.
Samsung S5 - Stock - Rooted
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