"Add one" to every color in an image
Mathematica, 78 bytes

Image@Apply[16#+#2&amp;,Mod[IntegerDigits[#~ImageData~"Byte",16,2]+1,16]/255,{3}]&amp;


Takes and returns an image object (to create an image object, just paste the image into Mathematica).

Result for the test case:



Taking input and returning output as a 3D array of integer channel values, this reduces to 51 bytes:

Apply[16#+#2&amp;,Mod[IntegerDigits[#,16,2]+1,16],{3}]&amp;


But those meta posts don't have an overwhelming amount of support yet, so I'm going with the 78-byte version for now.