Krylon mat finish spray. Do not confuse it with Krylon photo dulling spray, that won't work. Mat finish spray is a great spray for inexpensive photos, it will hide fingerprints and other minor damage. This will NOT work on computer generated ink jet prints, it will ruin them. If you spray it on a regular photo print, you can sometimes get a white blushing or fog. Just let it dry completely for a few hours. In the meantime chill the Krylon can in the refrigerator, then re-spray the photo. That should remove the fog or blushing.
You can also remove the entire Krylon spray coating by using pretty much any non photochemically reactive solvent. Make sure it says that on the can somewhere. This will also serve as a test to see if it really was an actual photographic print rather than ink jet. It won't hurt the photo at all, it will destroy the ink jet print.
Krylon mat spray is especially handy if you have to put a photographic print directly against the glass, as in photo frames. It will prevent the print from fusing to the glass. Make sure the spray coating is completely dry before fitting it.
John