Rich Felker wrote:
On Fri, Aug 04, 2006 at 02:05:00PM +1000, Russell Shaw wrote:
Subpixel only works on LCDs, which produce ugly output.
I think sub-pixel rendering also works for a crt, but a sudden change
in pixel value (such as the edge of a black square on a white background)
is smeared (convolved with the step response of analog electronics
bandwidth) into a few pixels on the crt. It shouldn't make sharpness any
>>worse.
No, this is absolutely incorrect. Subpixel is fundamentally impossible
on a CRT because the CRT's rgb cells have nothing to do with the video
card's idea of "pixel". You can enable it and the degree to which it
looks bad will depend on a lot of factors, but it's most certainly not
doing what subpixel is intended to do.
Not so. The videa card DAC is putting out an analog signal that is a
readout of consecutive pixel values from the video ram.
The analog signal passes through various stages that cause the voltage
from a single pixel to contribute to other pixels next to it, so that
all video-ram pixels end up contributing overlapping values in a horizontal
direction on the crt. The amount of overlap depends on the analog bandwidth
of all the amplifiers and cable between the video DAC and electron gun.
(The crt gun output is the convolution of the DAC output and intermediate
channel impulse response).
Also it does not give more vertical resolution which is actually what's
>>>needed in certain scripts for small fonts to look good.
It does give the effect of extra vertical resolution.
No it does not. If you claim this you should back it up with an
explanation.
I have. There is effectively antialiasing with a granularity of single r/g/b
cells instead of rgb triplets (or whole pixels).
The effect is that of a small amount of sub-pixel antialiasing, making
>>sloping lines look less jaggered.
Yes, sloping lines. This is because the increase in resolution is
horizontal, not vertical.
What i mean is that even though the increase in resolution is horizontal,
that still makes sloping lines less jaggered.
With a black edge on a white background, sub-pixel rendering makes the
>>individual r/g/b sub-pixels go from 100%(white)->67%->33%->0%(black).
Full-pixel anti-aliasing is what really wrecks the sharpness and darkness
of a glyph.
It sounds like everything you're saying comes from a very vague
understanding from a user standpoint rather than knowing what the
terms actually mean and what they do..
Well, since designing analog and radio-frequency electronics from when i was
10 and still doing it daily, i have a somewhat detailed understanding of it all.
--
Russell Shaw, B.Eng, M.Eng(Research)
--
Linux-UTF8: i18n of Linux on all levels
Archive: http://mail.nl.linux.org/linux-utf8/
