load/save .ANS files

[saulpw]

This would be super useful for any kind of interop outside of VisiData.

ref #11

[AdrianGroty]

I believe saving is already implemented in save_ans.py. It only works if there are no frames or frame values, iirc.

[AdrianGroty]

ANSI art, as it turns out, is more of a loose suggestion of a format than a standard, despite its namesake. Here is a list of compatibility considerations. The ones I've encountered so far, anyway.

• CP437
• UTF-8
• 16-color codes
• 256-color codes
• PabloDraw 24-bit RGB codes
  • ESC[(0|1);R;G;Bt
  • 0=bg, 1=fg, RGB=(0-255), t terminator
  • always follows a 16-color code
  • overrides preceding 16-color code
• cursor positioning codes
  • some ANSI use positioning codes instead of newlines
• styling codes
• iCE colors/blinking
  • contemporary terminals use [5m and [6m for blinking
  • period ANSI would blink if a bright bg was used
  • or blinking was disabled to allow bright bg
  • but never both
• one-line files which rely on 80-column wrap
  • some ANSI have no explicit line advancement
  • and assume it will happen automatically every 80 columns
• Amiga?
  • character mapping is a bit different
• SAUCE record?
  • documentation

Might as well include

• ANSI music
  • certain viewers (maybe just one) could play back PC speaker music sequenced in the escape codes
  • documentation
  • also documentation

[AdrianGroty]

The current ANSI-saving implementation also seems to have some issues. (My bad!) If no color is specified for an object in DarkDraw, the output .ans will assume 7 (light grey) instead of using the terminal default. Colors and style codes are also sometimes lost in the conversions, but not consistently, and I'm not sure why.

I've attached a simple test of the various style escape codes and a doodle that loses some style codes in conversion, both in .ddw and .ans format.

ans_save_issue.zip

[AdrianGroty]

Legacy Update: widths other than 80 were also standard, and 80 cannot be assumed of an inline ANSI file. My understanding is that most modern softwares that open or operate on ANSI art have a way to manually set the line wrap because there's just no way to do this consistently via parsing.