I'm currently in the middle of creating a graphics hack for the NES game, The Last Starfighter (MSX Uridium sprites) using YY-CHR. Just wondering how to create a patch from the hack?
When you have your hack ready, you will also need the original Rom of it. Open Lunar IPS, select Create patch. When it asks for Original Rom, choose the original Rom file, and when it asks for the Modified Rom, choose your hack. Then it will ask for the name of the IPS. That's it.
This IPS will then contain all the changes you made to the game. Changes only and can be applied to original Rom. But you also need to drop the original rom you used into the hash calculator to look up the CRC-32 id. The users need to use the exact same original Rom to patch to. If they don't use the exact same one, the result will be a bugged rom.
Additionally you can choose other formats like UPS, xdelta etc, which also include the security check, since they remember the CRC of the original rom and the info is in the patch itself, so users can not patch wrong, they can only get a "CRC target mismatch".