crop images in Flex

[abhishek]

hey frnds,
I have 1 query,
user is uploading 1 image , on it i have 1 transparent image like
phone front side image.
user should see only that part of 1st image which comes under the
above transparent image.
User can adjust image image and can see a part of uploaded image which
comes exact under of above transparent image.
Then i want to crop this part which is showing now. Means i want to
cut or crop only that part of uploaded image which is visible now.
Plz tell me how can i do this,

same like this site
https://www.gelaskins.com/skinner.php
thx in advanced,
:)