How to get the pixels that are surrounded with Rectangle?

I have some silverlight page and on him i have some Rectangle. I fill up this Rectangle with some ImageSource and i created small Rectangle that can move across the imageSource.

Now, I the user need to press on "OK" button and the ImageSource that will be surrounded with the moving Rectangle need to copy to some other page.

My question:

1. I don't know how to fine the location of the 'moving Rectangle' in the right Scale that is the Scale of the Rec开发者_如何学运维tangle that fill up with the ImageSource.

2. Because i want to copy the surrounded pixels to some new Image ... How can i locate the surrounded ImageSource ?

I had this problem a long time ago under WPF and not SL.. I couldn't find the code for it but I do remember that the following link helped me allot.

http://www.codeproject.com/KB/WPF/CropAdorner.aspx