Wanted to follow up and say that while including the proprietary Instagram shaders is wrong, the author did a nice job with this.

We're currently working on some filtering stuff using GPUImage as well, and it's nice to see this stuff progress.

One filter that is missing here BTW is Lux, which is Instagram's equivalent of the Camera+ Clarity filter. The reason (I suspect) is that the Lux "filter" is actually not implemented using shaders, but rather CoreGraphics.

Would love to hear your take on it if you know more.