Like the Threshold value, the Flare Intensity has both a slider and a text input field for specifying its value. This button may or may not have much effect on an image. However, pressing this button will provide a new value to be computed for the saturation of each pixel. In practice I couldn't see much difference between the two, but the code was there from John's original code, so I thought I'd add the ability to choose one or the other. This is simply the maximum length of the spikes in pixels.
Larger values mean longer spikes radiating from a pixel.
The length is computed to be exact in the X and Y directions, but obviously the number of pixels at 45 degree angles from these axis' won't be exactly the length value. This value determines the number of spikes to radiate from a pixel. The default value of 6 was used for the example images and appears to be a fairly reasonable value. Larger values might produce some interesting effects, including feathering around a set of points. This is the angle between each spike.