[R] Remove "gray grid" from levelplot

[Prof Brian Ripley]

On Mon, 6 Mar 2006, Martin Sandiford wrote:

[...]

> P.S. To me, the png() device does not appear to do sub-pixel
> rendering.  The postscript() and pdf() devices do.

What could you possibly mean by that?

The postscript() and pdf() produce vector graphics and have no concept of 
a pixel.  There are filled polygons as part of the language they output. 
(Of course the coordinates are output to finite resolution, in fact 0.01dp 
= 1/7200", so you could think of that as the positioning quantum.)

The png device writes on a bitmap.  It outputs a rectangular grid of 
either pre-defined colour indices or RGB values.  There is nothing in the 
PNG standard to allow anything finer.

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595