How can I select parts of an Image

How can I select parts of a Big Image.bmp?

I want add a image control in order to see the zones I choose of a big image, something ike a zoom. The "cNnormalImage" propiety just pick the upper-left corner of the image, is there any other posibility?

Thanks in advance:sign0085:

See this post: http://www.b4x.com/forum/showthread.php?p=1617