How to recolor an image on specific area?
<p>I'm trying to create an iOS recoloring app (<a href="https://itunes.apple.com/us/app/recolor-coloring-book-for/id1027352017" rel="nofollow">this is my reference</a>), and i need to know how recolor some portion of the image when user taps on a given area. All the loaded pictures will be black/white initially.</p>

<p>Is there any prebuilt library? Or which graphics framework should i use?</p>

<p>Any help will be appreciated.</p>