The way filters are set is a bit confusing by setting the effect property to a string:
image.fill.effect = "filter.name"
Once this is set, image.fill.effect is not a string, but a user data object!
Then to set the filter parameter(s):
image.fill.effect.paramName = paramValue
This could be even more confusing or impossible if multiple filters (highly desired feature) are applied.
Something like this would be much simpler:
Also, is there a way to disable a filter effect or reset the image? I tried setting image.fill.effect to nil and empty string without success.