使用MVVM，当控件没有“Command”属性时该怎么办？

In my program I need a way to click on an Image control, the program takes in the X,Y position of where the click took place, and then produce a rectangle around that position. My problem is that I'm using MVVM, so all my code is in a separate file (ViewModel file rather than the code-behind file). The Image control doesn't have a Command property so what's the best way to implement this?In my program I need a way to click on an Image