altscribe 0.1.1

AI-powered WCAG 2.1 AA compliant image alt-text generator for documents via pandoc

altscribe

AI-powered, WCAG 2.1 AA compliant image alt-text generator for documents — built on pandoc and Claude.

Designed for California State University faculty to meet accessibility obligations under ADA Title II, Section 508, and the CSU Accessible Technology Initiative.

Features

• Automatic image classification — detects decorative, informative, functional, complex, and text images per the W3C WAI Images Tutorial
• WCAG 2.1 Level AA compliant (SC 1.1.1 Non-text Content, SC 1.4.5 Images of Text)
• Context-aware — passes surrounding text and section headings to the model for better descriptions
• Complex image support — generates both short alt-text and structured long descriptions for charts, graphs, and diagrams
• Functional image detection — identifies images inside links/buttons and describes the action, not appearance
• Decorative image handling — produces empty alt="" for non-informational images
• Images of text — transcribes visible text verbatim
• Any format in, any format out — leverages pandoc to read and write Markdown, HTML, DOCX, RST, LaTeX, and more

Installation

Prerequisites

• Python 3.10+
• pandoc installed and on PATH
• An Anthropic API key

Install from PyPI

pip install altscribe

Install from source

git clone https://github.com/ahb-sjsu/altscribe.git
cd altscribe
pip install -e .

Usage

# Set your API key (or pass --api-key)
export ANTHROPIC_API_KEY=sk-ant-...

# Process a Markdown file
altscribe lecture-notes.md -o lecture-notes-accessible.md

# Convert HTML to accessible Markdown
altscribe syllabus.html -f html -t markdown -o syllabus.md

# Regenerate alt-text even for images that already have it
altscribe slides.md --overwrite -o slides-fixed.md

# Output to stdout
altscribe document.md

Options

Flag	Description
-o, --output FILE	Output file path (default: stdout)
-f, --from FORMAT	Pandoc input format (default: auto-detect)
-t, --to FORMAT	Pandoc output format (default: markdown)
--api-key KEY	Anthropic API key (or set ANTHROPIC_API_KEY)
--overwrite	Regenerate alt-text for images that already have it

How It Works

1. Parse — reads the input document into a pandoc AST via panflute
2. Walk — traverses every Image node in the document
3. Classify — sends each image to Claude's vision API, which classifies it into one of five W3C WAI categories (decorative, informative, functional, complex, text)
4. Generate — produces category-appropriate alt-text:
   • Decorative: alt=""
   • Informative: concise description under 125 characters
   • Functional: describes the action/destination of the parent link or button
   • Complex: short alt-text plus a structured long description inserted after the image
   • Text: verbatim transcription of all visible text
5. Output — writes the modified document in any pandoc-supported format

Compliance

altscribe is designed to satisfy the following standards as they apply to CSU:

Regulation	Standard	Deadline
ADA Title II (2024 Final Rule)	WCAG 2.1 Level AA	April 24, 2026
Section 508 (Revised 2017)	WCAG 2.0 Level AA	Ongoing
California Gov. Code 11135	Section 508 compliance	Ongoing
California AB 434	WCAG 2.0 Level AA+	Biennial
CSU Executive Order 1111	CSU ATI Policy	Ongoing

WCAG success criteria addressed

• 1.1.1 Non-text Content (Level A) — all images receive appropriate text alternatives
• 1.4.5 Images of Text (Level AA) — text in images is transcribed verbatim

Image handling per W3C WAI guidelines

Image type	alt-text strategy	Long description
Decorative	alt=""	No
Informative	Concise description	No
Functional	Action/destination label	No
Complex (charts, diagrams)	Short identifying label	Yes — inserted as adjacent text block
Images of text	Verbatim transcription	No

Note: AI-generated alt-text should be reviewed by a human for accuracy. altscribe is a productivity tool that drafts compliant alt-text — final responsibility for accessibility rests with the content author.

Development

# Install dev dependencies
pip install -e . ruff black pytest

# Run tests
pytest tests/ -v

# Lint
ruff check src/ tests/

# Format
black src/ tests/

License

MIT