 Sample image
The task is to demonstrate the creation of a series of vertical pinstripes across the entire width of the display.

 in the first quarter the pinstripes should alternate one pixel white, one pixel black = 1 pixel wide vertical pinestripes
 Quarter of the way down the display, we can switch to a wider 2 pixel wide vertical pinstripe pattern, alternating two pixels white, two pixels black. 
 Half way down the display, we switch to 3 pixels wide, 
 for the lower quarter of the display we use 4 pixels.


c.f. Colour_pinstripe/Display

   load'viewmat'
   NB. size=. 2{.".wd'qm'          NB. J6
   NB. size=. getscreenwh_jgtk_ '' NB. J7
       size=. 3{".wd'qscreen'      NB. J8
   'rgb'viewmat- (4<.@%~{:size)# ({.size) $&> 1 2 3 4#&.> <0 1