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27 , 2001
Try entering the formulas you see below.
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 sliderctl(0)minus the second sliderctl(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.
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.)
2: channel shifting
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 movedynamically and interactively, of course.
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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