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    Customizable color text formatting with presets for ANSI & HTML.

    This package provides a number of color and other styling format constants, as well as formatting functions to interpret and apply these abstract format identifiers for different output formats.

    Format identifiers

    The format constants provided by this package are primarily (not exclusively) aimed at being used with the package. The text canvas stores all characters in a Uint32Array with the lower 16 bits used for the UTF-16 code and the upper 16 bits for abitrary formatting data.

    The format IDs provided here are tailored for some of the included ANSI & HTML formatters, but users are free to choose use any other interpretation (but then will also need to implement a custom string formatter impl).


    These color IDs MUST be prefixed with either FG_ (foreground) or BG_ (background):

    • BLACK
    • RED
    • GREEN
    • YELLOW
    • BLUE
    • CYAN
    • GRAY
    • WHITE

    Stylistic variations

    • BOLD
    • DIM

    Combined formats

    Format IDs can be combined via the binary OR operator, e.g.:



    These above listed built-in format IDs are only compatible with these bundled formatters (described below):

    • FMT_ANSI16

    String conversion format presets

    String formatting is completely customizable via the StringFormat interface. Currently the following presets are supplied:

    • FMT_ANSI16 - translate built-in format IDs to 4-bit ANSI escape sequences
    • FMT_ANSI256 - uses all 16 format bits for fg & bg colors (ANSI esc sequences)
    • FMT_ANSI565 - uses all 16 format bits for RGB565 fg colors (ANSI esc sequences)
    • FMT_ANSI_RAW - verbatim use of format IDs to ANSI sequences
    • FMT_HTML_INLINE_CSS - HTML <span> elements with inline CSS
    • FMT_HTML_TACHYONS - HTML <span> elements with Tachyons CSS class names
    • FMT_HTML565 - HTML <span> elements with RGB565 color coding
    • FMT_NONE - dummy formatter outputting plain text only (all format information discarded, e.g. for NO_COLOR support)

    256 color ANSI format

    If targeting this output format, all 16 bits available for formatting information are used to encode 2x 8bit foreground/background colors. Therefore, none of the above mentioned preset color names and/or any additional formatting flags (e.g. bold, underline etc.) cannot be used. Instead, use the format256() function to create a format ID based on given FG, BG colors.

    ANSI256 color pallette

    Source: Wikipedia

    16bit color ANSI & HTML formats

    Similar to the above custom ANSI format, here all available 16 bits are used to store color information, but here in the standard RGB565 format (5bits red, 6bits green, 5bits blue). This too means, only either the text or background color(1) can be controlled and no other formatting flags (bold, underline etc.) are available.

    (1) In the ANSI version it's always only the text color.

    These formats are primarily intended for image display, see the readme for usage examples...

    Ad-hoc formatting of strings

    String formatters can also be used in an ad-hoc manner, without requiring any of the other text canvas functionality.

    // create & use a HTML formatter
    defFormat(FMT_HTML_INLINE_CSS, FG_LIGHT_RED | BG_GRAY)("hello")
    // "<span style="color:#f55;background:#555;">hello</span>"
    // create & use an ANSI formatter
    defFormat(FMT_ANSI16, FG_LIGHT_RED | BG_GRAY)("hello")
    // "\x1B[91;100mhello\x1B[0m"
    // ANSI syntax sugar (same result as above)
    defAnsi16(FG_LIGHT_RED | BG_GRAY)("hello")
    // "\x1B[91;100mhello\x1B[0m"

    Furthermore, defFormatPresets() can be used to create formatting functions for all 16 preset foreground color IDs for a given string format strategy:

    const ansi = defFormatPresets(FMT_ANSI16);
    `${"hello")} ${ansi.lightRed("world")}!`;
    // '\x1B[32mhello\x1B[0m \x1B[91mworld\x1B[0m!'
    const html = defFormatPresets(FMT_HTML_TACHYONS);
    `${"hello")} ${html.lightRed("world")}!`;
    // '<span class="dark-green ">hello</span> <span class="red ">world</span>!'


    STABLE - used in production

    Search or submit any issues for this package

    Related packages

    • - Text based canvas, drawing, tables with arbitrary formatting (incl. ANSI/HTML)


    yarn add

    ES module import:

    <script type="module" src=""></script>

    Skypack documentation

    For Node.js REPL:

    # with flag only for < v16
    node --experimental-repl-await
    > const textFormat = await import("");

    Package sizes (gzipped, pre-treeshake): ESM: 1.71 KB


    Usage examples

    Several demos in this repo's /examples directory are using this package.

    A selection:

    Screenshot Description Live demo Source
    3D wireframe textmode demo Demo Source
    Textmode image warping w/ 16bit color output Demo Source


    Generated API docs



    Karsten Schmidt

    If this project contributes to an academic publication, please cite it as:

      title = "",
      author = "Karsten Schmidt",
      note = "",
      year = 2020


    © 2020 - 2022 Karsten Schmidt // Apache Software License 2.0


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