RadImageEditor is an extensible control and you can define custom tools and adorners. We have not implemented touch support for RadImageEditor and it is possible that there may be some setbacks, as touch is not tested and officially supported yet.
However, in case you still want to give it a try, I am attaching an example of how a custom tool can be implemented. In the sample, I have included the default CropTool, just that I have renamed it and used it as a custom one. The example is for Silverlight, but it should be fairly easy to copy the two classes and use them in a WPF application. I hope this helps.
the Telerik team
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