Grayness

This is a proof of concept typst wasm-plugin to allow simple image editing functions from within typst, written in Rust. It uses the wasm-minimal-protocol crate to define the plugin functions. The image editing functionality is provided by the image crate.

Usage

The simplest way to use this plugin is to import the package grayness into your typst code and use it's wrapper functions:

#import "@preview/grayness:0.1.0":*
#let imagedata = read("path-to-your-picture.jpg", encoding: none)
#grayscale-image(imagedata)

The manual provides further details.

You can also use this plugin directly, e.g. if you have compiled the wasm binary yourself.

This plugin provides the following functions:

• blur(imagebytes, sigma): performs a Gaussian blur on the image. Sigma is a measure of how much to blur by.

  Warning: This operation is SLOW

  Example usage:

  #let pl = plugin("gray_ness.wasm")
  #image.decode(
    pl.blur(
      read("example.jpg",encoding: none), //read raw bytes from file
      bytes("10") //specify bluring amount. Integers need to be converted to bytes from string
    )
  )
  

• convert(imagebytes): used to display filetypes not directly supported by typst such as WebP by converting to PNG internally.

  Supported filetypes:

  • Bmp
  • Dds
  • Farbfeld
  • Gif
  • Hdr
  • Ico
  • Jpeg
  • OpenExr
  • Png
  • Pnm
  • Qoi
  • Tga
  • Tiff
  • WebP

Example usage:

#let pl = plugin("gray_ness.wasm")
#image.decode(
  pl.convert(read("example.webp",encoding: none))
)

• crop(imagebytes, startx, starty, width, height): crop the image starting from the given x,y coordinates (top left corner) to the specified width and height from there. All values are in pixels

  Example Usage:

  #let pl = plugin("gray_ness.wasm")
  #image.decode(
    pl.crop(
      read("example.jpg",encoding: none), //read raw bytes from file
      bytes("10"), //start x location in pixels
      bytes("20"), //start y location in pixels
      bytes("100"), //width in pixels
      bytes("200") //height in pixels
    )
  )
  

• grayscale(imagebytes): turn the image into a black-and white version of itself

  Example Usage:

  #let pl = plugin("gray_ness.wasm")
  #image.decode(
    pl.grayscale(
      read("example.jpg",encoding: none)
    )
  )
  

• flipv(imagebytes): flip the image vertically

  Example Usage:

  #let pl = plugin("gray_ness.wasm")
  #image.decode(
    pl.flipv(
      read("example.jpg",encoding: none)
    )
  )
  

• fliph(imagebytes): flip the image horizontally

  Example Usage:

  #let pl = plugin("gray_ness.wasm")
  #image.decode(
    pl.fliph(
      read("example.jpg",encoding: none)
    )
  )
  

• transparency(imagebytes, alpha): add (or change) the transparency of the image to the level given by alpha (0-255)

  Example Usage:

  #let pl = plugin("gray_ness.wasm")
  #image.decode(
    pl.transparency(
      read("example.jpg",encoding: none), //formats without transparency support will be converted to PNG
   bytes("128") //50% transparent
    )
  )
  

Compile

To compile this plugin, you need to have a working Rust toolchain. Then you need to install the wasm32-unknown-unknown target:

rustup target add wasm32-unknown-unknown

Then, build the crate with this target:

cargo build --release --target wasm32-unknown-unknown