Joost van Schaik posted a solution he developed for multi touch pan/zoom behaviour for Multi Scale Images on Windows Phone 7.
Some may have read my foray into using Windows Phone 7 to view maps, utilizing a Multi Scale Image
(msi), MVVM Light and some extension properties. This application works quite
well, but being mainly a study in applied architecture, the user experience
leaves much to be desired. Studying Laurent Bugnion’s Multi Touch Behaviour got me on the right track. Although
Laurent’s behaviour is very good, it basically works by translating, resizing
(and optionally rotating) the control(s) inside the FrameworkElement is is
attached to. For various reasons this is not an ideal solution for a map viewer.
So I set out to make my own behaviour, the first one I ever made by the way,
and it turned out to remarkably easy – less than 90 lines of code, including
whitespace and comments.