Machines · Study 074
Dot Matrix Marquee
An amber dot matrix sign scrolls messages and the current time across a grid of round lamps. Your pointer sets the scroll speed.
What you're looking at
The message is first drawn as ordinary text onto a hidden canvas sixteen pixels tall. The sign then reads that image one pixel per lamp: a lamp is lit if the pixel beneath it is mostly opaque. Scrolling is just a matter of reading from a starting column that advances over time.
The idea behind it
Physical signs work the same way, with a controller shifting a bitmap along a matrix of LEDs or, in older signs, incandescent bulbs or electromagnetic flip discs. Sixteen rows is enough for legible capitals with a little room for descenders, which is why so many transit signs settled near that height.
Try this
Move the pointer left for a slow crawl or right for a fast one. Click or tap to skip to the next message.
