Speed up mosaicing using only a part

edit

Hi all! I'ma writing a program that make a mosaic from aerial videos. The obvious problem is that when the mosaic became larger, it takes more time to calculate feature. I've let run the program for 3 hour, but at a certain point an error comes out (like IDxONE and INTMAX stuff). So I though to take just a part of the mosaic for doing the calculation for speed it up and for avoid memory-based errors. I can extract the ROI with the instruction current_frame=Mat(mosaic,Rect(x,y,w,h)) and do the calculation, but the question is: How can I remap the point in the global mosaic coordinates?

Thanks!

I'm using visual studio 2013 and c++

EDITI'm using this code http://answers.opencv.org/question/60...