Better anti-aliasing

[Paul Fox]

bert wrote:
 > 
 > On 25.04.2008, at 15:07, Paul Fox wrote:
 > > unlike a traditional display, every pixel has a single color.
 > > given this, it seems wrong to talk about the "red channel of the
 > > first pixel".  you either use some of that pixel, or you don't.
 > > in effect, the display is implementing sub-(full-color-)pixel
 > > rendering all by itself.  (which i think is what bert was saying,
 > > but the "channel" thing confused me.)
 > 
 > In the display memory (a.k.a. framebuffer), each pixel has a red and a  
 > green and a blue value. I called these components "channel", which is  
 > not entirely correct. Still, the DCON selects only the red component  
 > of a framebuffer pixel to be displayed for a red physical pixel, the  

ah!  the missing piece.  thanks.  i was so focused on the display itself
that i'd never worked backwards to think about it from the
perspective of the framebuffer.

 > value of the green and blue components do not matter. If the 5-tap  
 > antialising filter is enabled, then the 4 adjacent pixel's red  
 > components are averaged, and mixed with the center pixel's red  
 > component. Again, the green and blue components are ignored, hence I  
 > spoke of "selecting". Makes sense?

yes.

 > 
 > > with the backlight off, this doesn't matter -- all pixels are the
 > > same color anyway.  but with the backlight on in monochrome mode,
 > > you see a lot of color in single-pixel-width lines.  if the line
 > > is perfectly aligned with the diagonal of the pixels, it will be
 > > completely colored (i just tried it), but mostly you just get a
 > > lesser or stronger fringing effect.
 > >
 > > for backlit ebook mode, this might not matter so much, since ebooks
 > > might not have a lot of diagonal single-pixel-width lines, but the
 > > effect is definitely there.
 > 
 > 
 > But it is greatly diminished by the antialiasing hardware filter. See  
 > if reading
 > 
 > 	http://wiki.laptop.org/go/Display
 > 
 > clears things up. With "selecting the red channel" I meant the DCON  
 > "swizzling" as described on that page.

yes, i see.

since this sub-topic came up in the context of using the
backlight in e-book (monochrome) mode, are you saying that the
unimplemented "swizzled not antialiased" mode would be better
than either of the two modes currently available ("monochrome"
and "swizzled antialiased")?

paul
=---------------------
 paul fox, pgf at foxharp.boston.ma.us (arlington, ma, where it's 70.7 degrees)