I use iFrame in my application in which I open other applications from different domains. I want to capture content of these applications either as raw text data or as an image (then I will apply OCR on this image).
This is correct. It's a major security issue when one webserver can reach out through a client and muck around with another webserver. In fact, a lot of the trouble we've been having with the CodeRanch JForum software lately stems from our work on plugging loopholes in that restriction that can come from a compromised client program.
You should be able to copy/paste and drag/drop manually between the IFrames, I believe, but automated data transfer and control is haram.
JSF doesn't work all that well with frames in any event, whether original-style or IFrame.
An IDE is no substitute for an Intelligent Developer.