Teletext separated mosaic graphics

William_J_G Overington wjgo_10009 at
Thu Oct 8 07:40:12 CDT 2020

Doug Ewell wrote:
> Of course, I can create a program or a protocol that takes ordinary 
> graphic characters such as < and >, and handles them in some special 
> way, but then I am creating a new layer on top of plain text.
So could the twenty-seven control characters in the 1976 teletext 
specification be encoded as ordinary displayable characters in plane 14 
such that they may, but need not, be used as control characters in such 
a program or protocol please?
Other codes used in later teletext formats and videotext formats could 
also be encoded if so desired.
By the way, I once had a page on viewdata. I saw an article on viewdata 
by Mr Fedida in an issue of the magazine Wireless World and I wrote to 
him enclosing a design for a page and he kindly arranged for it to be 
keyed in on page 786.
I saw it on a viewdata television in September 1977 and I wonder if it 
survives in an archive somewhere. I suppose that it is now part of the 
historic graphic art from that era.
I produced my design on a sheet of paper from one of those 
quadrille-ruled notebooks intended for arithmetic.
I used black ink for the text, one character per square, and red ink for 
the control codes, providing a key below the page diagram.
G for Alphanumerics Green, g for Graphics Green, and so on, H for Hold 
In fact, this design, which I called Colour Check, used only the seven 
graphic colour codes and the Hold Graphics code, and the graphic 
character corresponding to lowercase e.
There was a large red filled rectangle at the left, a large green filled 
rectangle at the right, and a large blue filled rectangle centred and 
lower  down the page. The top line of the green filled rectangle was not 
on the same line as the top line of the red filled rectangle: I am not 
sure whether it was higher or lower. The three filled rectangles 
overlapped and where the overlaps occurred the contiguous graphic 
characters were in yellow, white, magenta, cyan as appropriate.
A line typically started with a graphic colour code, green possibly, 
red, or blue according to which line, followed by a space and then a 
Hold graphics code. So where the control codes to change colour within 
the image occurred there was not a space displayed as the Hold Graphics 
facility repaced the space with a copy of the previous graphic 
The background was black and the fact that I used the graphic equivalent 
of a letter e produced the effect that the coloured areas were not solid 
filled but had a teletext-format look.
The graphic was centred, there was black to the left, to the right, 
above and below.
Some early teletext pages have been recovered from super-VHS tapes that 
had recorded television programs.
I am wondering if the early ITV Oracle graphic of the Blue Lady has been 
William Overington
Thursday 8 October 2020

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