Thumbnails : resize proportionally add borders

Hi,

I have a theme (that i bought on themeforest) that was using TimThumb.
I need all my thumbnails to be the exact same size (i use them as “featured images”) on the posts and on the excerpts. I need 100×100 squares, with the original ratio.

I already resize them before uploading using a resize application, but it doesent resize borders.
I used “Resize proportionally to fit entire image into specified dimensions, and add borders if required ” option in TimThumb http://www.binarymoon.co.uk/demo/timthumb-zoom-crop/

But now, the theme i have as made an update, and doesnt use TimThumb anymore.
Is there a way to do the same thing than before (Resize proportionally to fit entire image into specified dimensions, and add borders if required) with the wordpress cropping engine?
Or another way by modifying the code, using a plugin, or a program that resizes and add borders