[sixel] incorrect handling of HLS colors

[dnkl]

I was testing sixels in the HLS color space in several terminal emulators and noticed that wezterm doesn't handle them correctly:

Environment

• Linux Wayland
• wezterm 20210502-154244-3f7122cb

To Reproduce

Run img2sixel -t hls <image>. Compare with img2sixel -t rgb <same image>.

Expected behavior

Additional context

In Sixels, the primary color hues are:

• blue: 0°
• red: 120°
• green: 240°

I suspect wezterm uses

• red: 0°
• green: 120°
• blue: 240°

See https://archive.org/details/bitsavers_decstandar0VideoSystemsReferenceManualDec91_74264381/page/n927/mode/2up, or/and https://vt100.net/docs/vt3xx-gp/chapter2.html#S2.4.2 (scroll down to "Table 2-3 VT340 Default Color Map")

Also worth noting is that XTerm's implementation has issues too, but e.g. mlterm works as expected.

[wez]

Thanks for the report! I've pushed a change that fixes this for me!

[dnkl]

Works as far as I can tell. Thanks for the super quick fix!

[github-actions]

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