Typos: Rendering Typst Documents for Thermal Printers
A Go-based utility bridging Typst typesetting with ESC/POS thermal printing hardware.
1Solving Thermal Printing Limitations
The Typos project addresses the difficulty of handling CJK fonts on thermal printers. Standard ESC/POS code pages often fail to render Korean characters correctly. By bypassing internal printer fonts, this tool provides a more reliable method for printing complex documents, ensuring that specific language requirements are met without relying on limited hardware capabilities.
2Typst to Image Workflow
The core mechanism involves converting Typst documents into images before sending them to the printer. This rasterization approach allows for high-fidelity output that preserves the intended formatting of the original document. By treating the output as an image, the system avoids the common pitfalls associated with proprietary printer font sets and encodings.
3Go-Powered CLI Architecture
The project features a hand-written command-line interface built entirely in Go. This choice of language ensures efficient performance and cross-platform compatibility for users managing print jobs. The developer focused on creating a clean, modular codebase that handles the printer communication logic directly, providing a robust foundation for the entire document rendering pipeline.
4Optional REST Server Integration
Beyond the CLI, Typos includes an optional REST server designed for remote job management. This server utilizes an asynchronous job queue to handle incoming print requests efficiently. Users can leverage template support to automate document generation, making the tool suitable for environments where multiple print tasks need to be processed in sequence.
5AI-Assisted API Development
While the core printer logic was hand-written, the developer experimented with AI tools via Opencode to construct the REST API. This disclosure highlights a hybrid development approach where automation assisted in secondary feature implementation. The developer maintains full transparency regarding this process within the project's README file for all interested contributors.
6Focus on CJK Compatibility
The primary motivation for this development was the specific challenge of printing Korean text. Many thermal printers lack native support for the full range of CJK characters, leading to garbled output. Typos solves this by rendering the text as a graphic, effectively rendering the printer's internal font limitations irrelevant for the end user.
7Open Source Collaboration
The project is hosted on GitHub under the repository shlewislee/typos. The creator is actively seeking feedback from the developer community, specifically regarding code quality and architectural improvements. By opening the source, the developer invites contributions that could enhance the existing ESC/POS logic or expand the template support for various document types.
8Future Utility and Scope
Typos serves as a practical solution for developers integrating thermal printing into modern workflows. By bridging the gap between sophisticated typesetting tools like Typst and legacy hardware protocols like ESC/POS, it enables more versatile document output. Future iterations may focus on optimizing the image conversion process or adding support for additional printer models.
Original article: Hacker News: Show HN — Typos: Rendering Typst Documents for Thermal Printers