Pseudographics Nostalgia

According to the Wikipedia, "text-based semigraphics or pseudographics is a primitive method used in early text mode video hardware to emulate raster graphics without having to implement the logic for such a display mode."

When I was a child, I was obsessed with the text-based pseudographics of Teletext, especially when they looked like high contrast photos. Outside of Europe, Teletext never became popular, but in my home country the system still exists today. In the 2000s I even briefly worked as a Teletext editor for a Dutch public broadcasting network.

An acquaintance of my father had a television with a Teletext printer in the late 1980s. He could print his own "newspaper" with news that was just minutes old. Teletext was already a slow old-fashioned system in my childhood, but to me it was the future.

Teletext but also several computers from the early 1980s had a Mullard SAA5050-chip that made it possible to convert characters into patterns, a 2*3 block graphic.

Some channels got the most out of that chip. The Dutch "Teletekst" showed semigraphics every year in December with Holiday wishes.

During a thunderstorm, I discovered that bad reception revealed the alphanumeric characters behind the semigraphics. I was wondering if I could make the alphanumeric characters of every page visible by unplugging the antenna cable of the television. It worked. I wrote down the characters on a piece of paper and was able to convert them back into graphics on my computer, a Philips P2000t.

Now, many years later, the internet has an emulator for almost every computer from the 1980s. So I could finally do what I always wanted as a child. Converting a photo into semigraphics (comparable with 78*72 pixels in raster graphics.)

As an experiment I wrote a conversion program to convert a monochrome bitmap into a mode 7 program for the Acorn BBC Micro. This is the result, a "picture" of Mister Bean.

Semigraphical characters are still incorporated into the BIOS of any VGA compatible video card (▄? █ ?), so maybe I should work on a photo-to-text mode converter.