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Using the first six sliders—ctl(0) though
ctl(5)—to create a hue shift filter.

That's a hue shift filter. All it's saying is take the numeric value of the red, green and blue channels and add one slider value while subtracting another. In the case of red, we have the first slider—ctl(0)—minus the second slider—ctl(1). So whenever ctl(0) and ctl(1) are equal, you wind up with your original channel value. When ctl(0) is at 0, then ctl(1) is subtracted from the initial channel value. When ctl(1) is at 0, then ctl(0) is added to the initial value.

Video hue-shifted using Filter Factory.

You've just written your first filter. It doesn't do much, but it is keyframable, so you can cycle through hues just by changing the slider values as various keyframes. If you want, you can now save this filter to be used later. (See below for further instructions.)

Example 2: channel shifting
That wasn't so painful. Now let's try building upon this. Instead of changing the intensity of the individual channels, let's instead change the position of their pixels. In other words, we're going to separate the channels to achieve a sort of bad video effect that will have a look similar to a 3D movie.

Here, instead of using the values r, g and b in our R, G and B fields, we're going to use "src." To accomplish this, we need only state the x and y coordinates to which we want each channel's pixels to move—dynamically and interactively, of course.

The channel-shift effect.

Your formula will look like this for the R channel: "src(x-ctl(0),y-ctl(1))." This will allow you to shift the pixels in the R channel a number of pixels equal to the value of the first two sliders, ctl(0) and ctl(1).

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