I want to implement Ajax image upload and cropping function On my site.

You'll probably want to look for a jQuery (or other JavaScript) library which implements most of that functionality for you (preferably one that already works with CI, though that's optional). At that point, you would just need to adapt it to your site's specific needs and CI's upload library: http://www.codeigniter.com/user_guide/li...ading.html

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