code expand-rect  ( src dst w h --- )
   dx  pop              \ Height of source image in pixels
   4 [sp] edi xchg
   8 [sp] esi xchg
   begin
      0 [sp]  cx mov   \ Width of source image in pixels
      begin
         op: ax lods                \ Get a pixel
         op: ax d# 2400 [edi] mov   \ Write to next line
         op: ax stos                \ Write to this line + increment
         op: ax d# 2400 [edi] mov   \ Write to next line
         op: ax stos                \ Write to this line + increment
      loopa
      d# 2400 # edi add             \ Skip the next output line - already written
      edx dec
   0= until
   eax pop   \ Discard source width
   edi pop   \ Restore EDI
   esi pop   \ Restore ESI
c;