If only one of the previous examples is in your Image Unit folder, then everything works fine. The problem comes in when you have both of them in the Image Unit folder. In that case, neither show up in the UI. The problem is Core Image cannot uniquely identify the filters (i.e. it thinks they are the same, and gets confused.)
At first, I thought I just needed to add a unique bundle identifier to my Image Unit package. Unfortunately, that is not the case, which makes sense because you can have several filters in one Image Unit package.
The problem lies in the Description.plist. From the template, there are three keys which have the value “MyKernelFilter”, and one key which itself is “MyKernelFilter.” Two of the values and the key need to be changed to something unique.
If you look under the first key in the Description file, CIPlugInFilterList, you’ll see a dictionary of filter descriptions. You’ll note that in my examples, such as the HSB Mixer, I left the key for my filter description alone, as MyKernelFilter. I need to change it to be unique, like so:
Now that I’ve picked “HSBMixer” as my unique key, I need to replace MyKernelFilter with it in a couple of places, namely the CIFilterClass and CIKernelFile values. So at the bottom of the Description file:
CIHasCustomInterface didn’t change, I just left it in there because it was sandwiched between the two values that I did change.
That should cover it. If you rebuild and add both of the examples to your Image Units folder, they will both show up. This is pretty tedious work, so in future posts, I will just assume this is known and skip over it.