A MacOS Automator application that converts Keynote slides to PNGs.
The source included is just the single AppleScript action that performs the conversion in Keynote, the rest of the Automator Application is available within the Releases list.
Download key2png.dmg and double-click to open the disk image. Drag to "Applications" folder to install.
Run installed application "Slides to Images," select the Keynote (or PowerPoint or whatever) presentations you want to convert, then select the destination directory. After those selections are done, Keynote will launch for every necessary file and perform the conversion to individual PNG files.