Need to improve crop performance

[azagaya]

Hi! I'm developing an app in which i used OpenCV. Now I'm replacing all the opencv code for Cimg. So far i had no big problems. But something i noticed is that crop is much slower than the equivalent in OpenCV. I need to use crop because in some operations i need to extend the image with other images as neighbours, and apply a blur to all of them, and then crop the original image from it. Whish would be the best way to do this? I'm doing something like this:

current_parallax.crop(s.width(), s.height(), 2*s.width()-1, 2*s.height()-1);

where s.height() and s.width() are the size of the original image, surrounded by different neighbours of the same size.

I also tryed to define openmp, but i'm not sure how to do it. Is there any info about this?

Also, which would be the best way to apply som math operations to only a portion of the image? Im using Qt, and the app is being compiled dor windows, linux and mac.