carlos7ags / folio

Folio A modern PDF library for Go — layout engine, HTML to PDF, forms, digital signatures, barcodes, and PDF/A compliance. **Try it live in your browser** --- Install Requires Go 1.21+. One external dependency: . --- Quick Start --- HTML to PDF The fastest way to generate PDFs — paste any HTML template and get a PDF. No Chrome, no Puppeteer, no server required. Supports 40+ HTML elements, inline and block CSS, flexbox, CSS grid, SVG, named/hex/rgb colors, rules, and tables with colspan. **Try HTML to PDF live in your browser** --- Layout Engine Folio uses a plan-based layout engine — layout is a pure function with no mutation during rendering. Elements can be laid out multiple times safely, which makes page break splitting clean and predictable. Layout Elements | Element | Description | |---|---| | | Word-wrapped text with alignment, leading, orphans/widows | | | H1-H6 with preset sizes, spacing, and auto-bookmarks | | | Borders, colspan, rowspan, header repetition, auto-column widths | | | Bullet, numbered, Roman, alpha, nested | | | Container with borders, background, padding | | | Flexbox layout with direction, wrap, alignment | | | JPEG, PNG, TIFF with aspect ratio preservation | | | Horizontal rule (solid, dashed, dotted) | | | Tab stops with dot leaders (for TOCs) | | | Clickable text with URL or internal destination | | | Left/right floating with text wrap | | | Multi-column layout with automatic balancing | | | Explicit page break | | | Code128, QR, EAN-13 inline in layout | --- Styled Text --- Tables --- Barcodes --- Interactive Forms --- Digital Signatures Supports PAdES B-B, B-T (timestamped), and B-LT (long-term validation with embedded OCSP responses and CRLs). Also supports external signers (HSM, KMS) via the interface. Uses Go stdlib crypto. --- Reading and Merging PDFs --- Headers, Footers, Watermarks --- Standards and Compliance --- Colors --- CLI --- Architecture • **No mutation** during layout — elements can be laid out multiple times safely • **Content splitting** across pages via overflow elements • **Intrinsic sizing** via MinWidth/MaxWidth for auto-column tables • **Deterministic output** — byte-for-byte reproducible PDFs • **One external dependency** — --- Package Structure --- Roadmap • [ ] Template library — invoice, report, certificate, resume • [ ] Hosted cloud API — POST HTML, get PDF • [ ] Java SDK via Panama FFI • [ ] .NET SDK via P/Invoke --- Contributing Contributions welcome. Please open an issue before submitting large PRs. --- License Apache License 2.0 — see LICENSE.