koishi - v1.0.4

koishi

koishi: render Open Graph (og:image) SVG images from HTML strings and Lustre element trees, using the npm packages @comamoca/komeiji and satori.

Install the npm packages before use (see README):

npm install @comamoca/komeiji satori

Types

Font

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A font for satori rendering.

data is the raw font file bytes. satori accepts TTF, OTF, and WOFF (not WOFF2 — use .woff fixtures such as @fontsource’s .woff files).

pub type Font {
  Font(
    name: String,
    data: BitArray,
    weight: Int,
    style: FontStyle,
  )
}

Constructors 

  • Font(name: String, data: BitArray, weight: Int, style: FontStyle)

FontStyle

</> 
pub type FontStyle {
  NormalStyle
  Italic
}

Constructors 

  • NormalStyle
  • Italic

Options

</>

Rendering options. fonts must contain at least one font; satori fails with a SatoriError otherwise.

pub type Options {
  Options(
    width: Int,
    height: Int,
    fonts: List(Font),
    debug: Bool,
  )
}

Constructors 

  • Options(width: Int, height: Int, fonts: List(Font), debug: Bool)

PngError

</>

Error returned when SVG to PNG rendering fails.

pub type PngError {
  PngError(message: String)
}

Constructors 

  • PngError(message: String)

PngOptions

</>

Options for rendering an SVG to PNG with resvg.

Set width or height to a positive value to scale the output. If both are zero, the SVG’s intrinsic size is used. background accepts any CSS color string; use an empty string to keep the default (transparent).

pub type PngOptions {
  PngOptions(width: Int, height: Int, background: String)
}

Constructors 

  • PngOptions(width: Int, height: Int, background: String)

SatoriError

</> 
pub type SatoriError {
  SatoriError(message: String)
}

Constructors 

  • SatoriError(message: String)

Values

to_png

</> 
pub fn to_png(
  svg: String,
  options: PngOptions,
) -> promise.Promise(Result(BitArray, PngError))

Render an SVG string to a PNG image as a BitArray.

Uses the npm package @resvg/resvg-js (Rust resvg bindings).

koishi.to_png(svg, koishi.PngOptions(width: 1200, height: 0, background: ""))
// -> Promise(Result(BitArray, PngError))

to_svg

</> 
pub fn to_svg(
  html: String,
  options: Options,
) -> promise.Promise(Result(String, SatoriError))

Render an HTML string to an SVG string.

Internally: @comamoca/komeiji’s html() parses the HTML into a satori-friendly VNode, then satori() renders it to SVG.

koishi.to_svg("<div style=\"color:black;\">hi</div>", options)
// -> Promise(Result(String, SatoriError))
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