Forum Moderators: not2easy
So I agree completely with what was said above - you need to contact them and get their written permission. Most companies who are specialized in the field of picture sales are somewhat very sensitive when it comes to protecting their own content.
It seems that simple photoshop filters like blurring, sharpening, tweaking colors, etc (to say nothing of cropping or resizing) are NOT enough ... these companies make lots of money through intellectual property (their image sets), so they go to great lengths to protect it.
When the bots do help catch someone using their images illegally, I'm guessing a DMCA note followed by litigation happens next.
Best bet: get written permission. Or, don't use it. Or, spend the dough (tough to do, I admit).
If money's an issue, there are other sites with quality stock photos, at much lower prices (depends on the subject, of course).