x,y bounds of quadlet
[lox,hix,loy,hiy] = quadbounds(d,bx,by,n)
depth in splitting
box coordinates at that depth
extent of image
lower x-index of quadlet
lower y-index of quadlet
upper x-index of quadlet
upper y-index of quadlet
This routine is called by other, higher-level Wavelab functions and is not intended to be useful for most users.