PhotoX is a lightweight image viewer for Mac. Right click on a image and open with PhotoX. The image you selected is displayed at the center. The others in the same folder appear at the bottom as thumbnails. You can zoom, rotate, flip, and switch images. You can scale images and sort by name or date. You can copy, cut, move to trash, delete, get info, and more.
The app supports shortcut keys: ← = previous, → = next, ↑ = zoom out, ↓ = zoom in, esc = exit, and also supports zoom by mouse wheel.