How can I Center an image within a fixed specified crop frame with graphicsmagick C library

Hey, I was wondering if someone knows a good way to scale an image whi开发者_如何学JAVAle maintaining aspect ratio, and then center it with respect to a specified fixed crop area.

The first part is straight forward (resizing while maintaining ratio), just need help with the second part.

Here is a link to something that does this with php and image gd.. PHP crop image to fix width and height without losing dimension ratio

Another link to what I want to achieve is the "Crop" strategy on this page: http://transloadit.com/docs/image-resize#resize-strategies

I want to do this using the graphicsmagick C library.

Thanks a lot.