I have the same question.... I saw that this hasn't been replied to.
It doesn't realyl make sense to use RB on still images. The algorithm simply doesn't work that well if it cannot find any moving edges. You'll get much better results using Photoshop's Edge refinement tools, which have been greatly enhanced in CS5.
Thanks for your reply Mylenium!
I am stuck in a bit of a workflow catch 22...
Here's what I'm trying to do:
I have a bunch of slides (Powerpoint) in .pdf form. They go along with a video of the live presentation. I am overlaying the slides for better viewer visability and I am also animating them a bit since the lecturer uses a laser pointer, to point out specifics on the slides, but I lose that in the overlay, hence the added animation.
Since the slides are pretty cartoony, and roto/masking quality is really not much concern, the roto brush works pretty excellent for quickly singling out the subject matter I want the audience to focus on.
I have all the .pdf's in my comp, timed out and ready for animation. I am not sure how to get these .pdf's into, and back out of photoshop without having to line them up each time with the original (in this case, the original being the comp .pdf that I wanna use as the base for compositing on top of - since .pdf's are vector, they have no dimensions that carry over to photoshop) Maybe there's a workflow trick for this?... if not...
Then the roto brush works very fast, BUT freezing it treats the .pdf as footage, rendering each frame. How can I just apply it to the still, or just one frame, and stretch that frame?
Got Illustrator? You could also open a pdf in Illustrator, and select the appropriate paths to put them into separate Illustrator layers. When saved as an illustrator document and imported into AE as a comp, the Illustrator layers become AE layers. This means means you can do any number of things to them.
Of course, all bets are off if the pdf is nothing more than one big bitmap.
I think you are using the wrong tool for the job.
Photoshop CS5's Quick Selection Tool with Refine Edge will work better than RotoBrush on stills.
You could also try Photoshop's Background Eraser Tool. Even the terrible Magic Wand would probably yield acceptable results much much faster.
What if you can only afford one Adobe application, currently. I do motion graphics so I am logically, using After Effects. However, I can't afford the full CC package, also, I am not that familiar with Photoshop. Plus, no one has still yet answered the question of can it work with still images or not. I have used the roto brush tool on an image and it was able to outline the image perfectly in one small action... if I could figure out what to do next (by that, I mean turn the outlines into masks to be manipulated, independently, ect...) it would literally save me about hour of work. Instead of just advising me to use other programs such as Photo Shop and Illustrator, is there anyone who can try to answer this question for someone like me who can only afford one program right now? Thanks, guys.
Actually they have answered the question. Rotobrush will not work on still images. You can use all kinds of tools in AE to extract mattes. If you showed us a sample then we can point you in the right direction. Knocking out text against almost any background would be a very simple procedure if the text was mostly one color. If the background is one color it's easy as can be. Rotobrush only works if you have moving pixels.
is there anyone who can try to answer this question for someone like me who can only afford one program right now?
As Rick said, the question was answered sufficiently. Rotobrush is simply the wrong tool, but nothing stops you to use masks, mattes, effects and the conventional paint tools even on still images.