What is the theory behind the Light Glow effect of "After Effects"?

What is the theory behind the Light Glow effect of "After Effects"? I wanna use GLSL to make it happen. But if I at least get closer to the theory behind it, I could replicate it.

I will answer my own question just in case someone gets to here at the same point. With more precision (actually 100% of precision) I got to the exact After Effects's glow. The way it works is:

1. Apply a gaussian blur to the original image.
2. Extract the luma of this blurred image
3. Like in After Effects, you have two colors (A and B). So the secret is to make a gradient map between these color, acoording to the desired "Color Looping". If you don't know, a gradient map is an interpolation between colors (A and B in this case). Following the same vocabulary of After Effects, you need to loop X times over the "Color Looping" you chose... it means, suppose you are using the Color Looping like A->B->A, it will be considered one loop over your image (one can try this on Photoshop).
4. Take the luma your extract on step 2 and use as a parameter of your gradient map... in other words: luma=(0%, 50%, 100%) maps to color (A, B, A) respectively... the mid points are interpolated.
5. Blend your image with the original image according to the "Glow Operation" desired (Add, Multiply, etc)

This procedure work like After Effects for every single pixel. The other details of the Glow may be easily done after in basic procedure... things like "Glow Intensity", "Glow Threshold" and so on needs to be calibrated in order to get the same results with the same parameters.