Sixel Graphics

Telnet callers whose terminal has sixel graphics (xterm -ti vt340, mlterm, foot, WezTerm, Windows Terminal, iTerm2, SyncTERM and others) see the logo as a picture above the system's name. The logo is logo = /etc/bbs/logo.png, or, if that is not set, the system's name drawn in a pixel font.

The BBS asks every ANSI terminal for its device attributes (CSI c; sixel is attribute 4) and for its character cell size in pixels (CSI 16 t, to fit the logo to the window), so nothing changes for terminals without sixel. A caller can turn sixel off (or on, if their terminal has it) in their profile, and the choice is kept for their later calls.

sixel = auto is the default for telnet listeners, and no for raw and rlogin listeners, because a picture is slow over a modem.

Pictures

Pictures on the image boards are shown with sixel too. Terminals without sixel get the best they can show: kitty's graphics protocol on kitty and Ghostty, iTerm2's inline images on iTerm2 and mintty, and coloured half blocks on any other UTF-8 terminal with colour. Pictures on/off (M) in the profile turns them off for a caller. 3270s have their own ways of showing pictures, with vector graphics or blocks (see TN3270).

See also: TN3270 graphics, Configuration, Image boards