I’m having the same issue - can’t find the module via NPM. I’m using it in a bare react native project, and have done the pre-steps for unimodules installation (https://github.com/unimodules/core).
$ npm install --save expo-image-manipulator
npm ERR! code E404
npm ERR! 404 Not Found: expo-image-manipulator@latest
npm ERR! A complete log of this run can be found in:
npm ERR! .../.npm/_logs/2019-03-03T12_28_39_901Z-debug.log
...$ npm install --save expo-image-manipulator
npm ERR! code E404
npm ERR! 404 Not Found: expo-image-manipulator@latest