do i have to ask someone to post their picture?

The picture is his, you only edited it. Ask him if you can post the picture. It's very likely he's going to ask you to make sure you give him credit as the photographer, which is only fair. Label it specifically that you are just the editor. Do that for all the pictures you post, as it will save you a lot of headache in the future. Plus, by giving people credit, the likelihood of them using you again will rise significantly. Especially, if it also has the possibility of bringing them more business.

Both... You can post it and ask later... Its just photographs... Not a statement to ask or question...

A photograph always belongs to the one who took it unless there is a contract that tells otherwise. 

If you were the one who took the picture, sure, you can post it but again, that is unless there is a contract that tells you not to do so.

If you were the one who just manipulated the picture, you still do not own the photograph. You can not post the picture unless you are able to get consent from the photograph's owner.

If this is an example of you "fixing" it for him then you have a lot to learn. This photo is poorly done and it's out of focus.

As for your question, whoever took the photo owns the copyright, not you. If you're editing photos that you did not take you can be sued by the copyright owner. Just because you edit a photo doesn't mean it's yours.

The copyright laws in the United States (you do not mention where on the Earth you live, but I'll assume you're in the U.S.) clearly state that whomever takes the picture owns the copyrights.  Even if a complete stranger steals your camera and takes pictures with it, the thief owns the copyrights.

Therefore, since your friend pressed the button (or tapped the screen on a phone) he or she is the legal owner of the copyrights.  The fact that you edited or manipulated the image is irrelevant. 

Think of it this way:  You painted a great painting.  Over the years it has become tattered.  You take it to be restored.  The restorer fixes missing pieces of paint, cracks and puts the painting into a new frame.  Does the restorer own any rights to the painting?  No, of course not.  The restorer would need a signed release to use the painting to use as a promotion for his restoration business or anything else for that matter including taking photos of it.

As a side note, a very common misconception among the public is that if the photo is of them, then this somehow gives them the rights to do what they want with the image (e.g.  copying, editing, posting, etc...) which is 100% not true.  The fact that the photo is of you and that you paid for it is irrelevant.  Again, whomever presses the button owns the copyrights.