Fuzzy Fonts on TV
RWi...@acorn.co.uk
generating these things for the Archimedes range of RISC machines using UK
TV standards (more lines vertically). The short answer is *no* - the real
problem is that the number of pixels per inch vertically (around 45) is
inadequate for the use of anti-aliasing - the grey pixels are way too
obvious. [The answer can also be considered *yes* if you just have to have
an accurate representation of the typeface on this style of display].
[Archimedes machines provide 640x256 pixels with up to 8 bits per pixel on
UK TV standards.]
However, you don't need to do any of this if all you want is one, obviously
computer, font giving you 80 characters per line. Archimedes and its
predecessors - the BBC Microcomputer etc - can all manage to display a fully
legible 80 characters across using 640x256 and a carefully designed
character set [I know, I was that designer]. The basic technique used in the
computer to provide the display is a 16MHz pixel rate - far above what one
expects the TV to handle - and this does indeed cause colour aliasing if one
places different coloured pixels too close together (like adjacent! - which
gives an 8MHz square wave to the TV). I nullified this effect in the
character set design by making all vertical lines two pixels wide - reducing
the characteristic frequency to only 4MHz, easy enough for most TV sets. The
font is highly legible, capable of coping with being broadcast by a TV
station (the BBC, usually) and displayed on a cheap colour TV with a large
triad pitch. Naturally, connecting the computer straight to a TV is better
and using a monochrome TV better still.
Where can you get hold of this stuff? BBC machines were sold in the US for
some time, so perhaps there are unwanted second hand ones. Archimedes
machines are only sold in UK, Europe, Australia *and* Canada (by Olivetti -
ask for Dorothy Netherwood).
More (boring) information on anti-aliasing on Archimedes by popular demand.
But you really have to see it to believe in it! This article typed in on
Archimedes using 8 point on a 90 pixel per inch monitor.
Roger *if it ain't fuzzy it don't look right*
rwi...@acorn.co.uk
Peter da Silva
> The short answer is *no* - the real
> problem is that the number of pixels per inch vertically (around 45) is
> inadequate for the use of anti-aliasing - the grey pixels are way too
> obvious.
Doesn't this depend on the number of grey levels you have available?
--
Peter da Silva, Xenix Support, Ferranti International Controls Corporation.
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