Sixel

Sixel, short for "six pixels", is a bitmap graphics format supported by terminals and printers from DEC.

Each possible pattern is assigned an ASCII character, making the sixels easy to transmit on 7-bit serial links.

Sixel was first introduced as a way of sending bitmap graphics to DEC dot matrix printers like the LA50.

After being put into "sixel mode" the following data was interpreted to directly control six of the pins in the nine-pin print head.

The system was later re-used as a way to send bitmap data to the VT200 series and VT320 terminals when defining custom character sets.

Sixel encodes images by breaking up the bitmap into a series of 6-pixel high horizontal strips.

The "String Terminator" sequence ESC+\ returned the device back to normal character mode again.

The colors in the registers are defined using either RGB or HLS values in a peculiar DEC format.

Since the capabilities of the hardware vary widely, a color sixel drawing can only be output to targeted devices.