You can do it like this:
Code:
[VarSet,txtrInfo,""]
[VarSet,txtrWidth,0]
[VarSet,txtrHeight,0]
[VarSet,txtrInfo,[IGetInfo,Tool:Texture Map:TextureMap]]//this is the info that appears when the cursor is over the thumbnail
[VarSet,index,[StrFind,"Width=",txtrInfo]]//StrFind will return -1 if string not found
[If,index>-1,[VarSet,txtrWidth,[StrExtract,txtrInfo,index+6,index+10]]]
[VarSet,index,[StrFind,"Height=",txtrInfo]]
[If,index>-1,[VarSet,txtrHeight,[StrExtract,txtrInfo,index+7,index+11]]]
[Note,[StrMerge,"Texture Width = ",#txtrWidth,"\nTexture Height = ",#txtrHeight]]