ExtJs wind direction chart -

i want create wind direction chart, here example : http://www.windguru.com can't find how draw arrows on chart in extjs 4.

thank you

one way have image each direction of arrow (say 12 different images)

in grid, display image in cell

use template this:

<img src="/images/arrows/{direction}.gif"> 

and replace {direction} value store such "nw" north-west