samsa core

samsa-core

Library for processing TrueType font files.

Features:

• variations
• avar1 and avar2
• COLRv0 and COLRv1
• SVG generation
• shaping:
  • GSUB (includes basic ligatures and Emoji)
  • GPOS (includes class pair kerning with exceptions)
  • Feature Variations
  • script and language selection

This repo is for Version 2 development. Version 1 is managed in the Samsa GUI repo.

How to use

The essential steps are:

• load a font file into an ArrayBuffer
• create a SamsaBuffer object from the ArrayBuffer
• create a SamsaFont object from the SamsaBuffer
• create a SamsaInstance object from the SamsaFont
• call renderText() on the SamsaInstance to obtain SVG strings

Here is sample code for Node.js that loads filename from disk, creates a SamsaFont object, creates a SamsaInstance object with variation axes set to certain locations, renders the string hello, world! as SVG, then saves the SVG to the file render.svg.

const nodeBuffer = fs.readFileSync(filename);
const arrayBuffer = nodeBuffer.buffer;
const samsaBuffer = new SamsaBuffer(arrayBuffer);
const font = new SamsaFont(samsaBuffer);
const instance = font.instance({ wght: 900, wdth: 200 });
const svg = instance.renderText({ text: "hello, world!", fontSize: 72 });
fs.writeFileSync("render.svg", svg);

In a browser, you obtain an ArrayBuffer and process it similarly. The resulting SVG can be inserted into the DOM.

const samsaBuffer = new SamsaBuffer(arrayBuffer);
const font = new SamsaFont(samsaBuffer);
const instance = font.instance({ wght: 900, wdth: 200 });
const svg = instance.renderText({ text: "hello, world!", fontSize: 72 });
document.getElementById("myDiv").innerHTML = svg;

If loading a font file from a remote URL, you’ll probably use fetch() then response.arrayBuffer() to obtain the ArrayBuffer. If a font file is dragged onto the browser, the ArrayBuffer is obtained by enumerating the e.dataTransfer.items array, where e is the drop event. For each item in the array (there may be multiple items), if its kind property is equal to file, set file = item.getAsFile() and the promise file.arrayBuffer() will yield the ArrayBuffer.

Flow diagram

The diagram illustrates how Samsa creates a SamsaFont object from an ArrayBuffer, creates a SamsaInstance from the SamsaFont, then renders text as SVG.

flowchart TD
    F1[TTF] --> A[ArrayBuffer]
    F2[WOFF2] --> A[ArrayBuffer]
    A[ArrayBuffer] --> B[SamsaBuffer]
    B --> C[SamsaFont]
    B[SamsaBuffer] --> |"SamsaBuffer.decodeWOFF2()"| C[SamsaFont]
    C --> |"SamsaFont.instance(axisSettings)"| D(SamsaInstance)
    D --> |"SamsaInstance.renderText({text: myText, fontSize: mySize, color: myColor})"| E(SVG)

In use

• samsa-core v2 simple demo (CodePen)
• RenderStack (repo)
• figma-colrv1
• Samsa-GUI (repo, uses Version 1, upgrade planned)

Links

• GitHub repo
• npm package