random low contrast text with bayes

[Eric Shubert]

I've seen an uptick of spam lately with random low contrast (hidden) 
text. This appears to be lowering bayes probabilities.

I'd like to strip low contrast text from messages before they're learned 
by sa-learn in order to combat this.

1) does anyone have some guidance for building such a filter?

2) Is there perhaps a better way of dealing with this type of spam?

Thanks.

--
-Eric 'shubes'