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Listing 2-5 sets two input parameters—the input image and the input angle. Filters, except for generator filters, require an input image. Some require two or more images or textures. The input angle for the hue adjustment filter refers to the location of the hue in the HSV and HLS color spaces. This is an angular measurement that can vary from 0.0 to 2 pi. A value of 0 indicates the color red; the color green corresponds to pi/3 radians, and the color blue is 2/3 pi radians.

I was first alerted tot he mistake in that the measurements go from 0 -> 2pi, but in fact they had indicated two points that would appear in the first pi radians, and nothing in the second half of the circle. Thinking this is weird I pulled out my handy copy of art directors toolkit to check. pi/3 radians (60 degrees) is yellow, and not green, however 2/3pi radians (120 degrees) is green and not blue.

In fact, apple has made the simple mistake of not thinking in 2pi radian space. The values they are after are 2/3pi radians for green and 4/3pi radians for blue.

So it is with great joy, that I bring you this basic colour conversion table for the hue in an image.