This could be usefull, but wouldn't this result in a regular blur in images with more details/transitions? ... If you want to do a real bloom, you should first do a bright pass where you filter out the dark parts, then blur that and then mix it with the original image.

The pow() does a not-too-shabby job of filtering out the dark bits. The higher the exponent, the stronger the filter. But it's definitely all cheap fakery.

If you are interested I could send you a non-working example project.

Sure! :)