Content
# CHM to Markdown Converter
A Python utility for converting Compiled HTML Help (`.chm`) files into clean Markdown, with built-in support for multiple document types through a profile system.
Originally built for Autodesk Revit API documentation; the generic profile works with any CHM file.
## Features
- **Profile-based conversion** — `generic` profile for any CHM, `revit` profile for Autodesk Revit API docs
- **Auto encoding detection** — handles UTF-8, GB18030, GBK, GB2312, and more via `chardet`
- **Cross-platform 7-Zip detection** — finds `7z`/`7za`/`7zz` on PATH (Windows, Linux, macOS)
- **Flexible CHM structure support** — handles `html/` subdirectory, flat, and deeply nested layouts (e.g. DirectX SDK)
- **`--preserve-structure`** — optionally mirrors the CHM's internal folder hierarchy in the output instead of flattening everything into `data/`
- **Code block preservation** — detects language from class names and named divs; supports C#, VB, C++, F#, Python, Java, JS/TS, Bash, SQL, XML, JSON
- **Table normalization** — cleans and re-formats Markdown tables
- **Index generation** — produces `file_index.json`, `id_lookup.json`, and `index.md` for search and AI integration
- **Async + batched processing** — bounded concurrency and periodic GC prevent memory overflow on large CHM files (6 000+ pages)
## Project Structure
```
chm_converter/ # Core package
├── config.py # ConversionConfig dataclass + built-in profiles
├── encoding.py # Encoding detection (chardet + CJK fallbacks)
├── extractor.py # CHM extraction via 7-Zip; HTML folder detection
├── html_processor.py # HTML cleaning, link rewriting, code block extraction
├── md_converter.py # HTML → Markdown conversion + post-processing
├── indexer.py # File dictionary building + index file generation
└── pipeline.py # High-level async pipeline (process_chm_file, process_all_chm_files)
chm_to_markdown.py # CLI entry point
resources/ # Place CHM files here
output/ # Generated Markdown (created automatically)
```
### Output layout
```
output/
└── <name>/
├── core/
│ ├── file_index.json # id → {title, filename, version}
│ ├── id_lookup.json # lowercase id → {title, filename, keywords, version}
│ └── index.md # alphabetical navigation page
└── data/
├── Topic1.md
├── Topic2.md
└── ...
```
## Requirements
- Python 3.10+
- [7-Zip](https://www.7-zip.org/) — `7z` must be reachable via the default install path or `PATH`
- Windows: installs to `C:\Program Files\7-Zip\7z.exe` by default, or add to `PATH`
- Linux: `sudo apt install p7zip-full`
- macOS: `brew install p7zip`
## Installation
```bash
git clone https://github.com/DTDucas/chm-converter.git
cd chm-converter
pip install -r requirements.txt
```
## Usage
Place `.chm` files in the `resources/` folder, then run:
```bash
# Interactive menu (lists available CHM files)
python chm_to_markdown.py
# Convert a single file
python chm_to_markdown.py --single resources/docs.chm
# Convert all CHM files in resources/
python chm_to_markdown.py --all
# Use the Revit API profile (strips Revit help-viewer boilerplate)
python chm_to_markdown.py --all --profile revit
# Preserve the original folder hierarchy inside data/ (e.g. for DirectX SDK)
python chm_to_markdown.py --single resources/directx_sdk.chm --preserve-structure
# Keep extracted HTML for debugging
python chm_to_markdown.py --single resources/docs.chm --keep-html
# Tune performance
python chm_to_markdown.py --all --workers 4 --batch-size 25 --semaphore 10
```
### CLI arguments
| Argument | Short | Default | Description |
| ---------------------- | ----- | --------- | --------------------------------------------------------------- |
| `--single FILE` | `-s` | — | Convert a single CHM file |
| `--all` | `-a` | — | Convert all CHM files in `resources/` |
| `--profile` | `-p` | `generic` | Conversion profile: `generic` or `revit` |
| `--keep-html` | `-k` | off | Retain extracted HTML after conversion |
| `--workers N` | `-w` | `8` | Thread-pool size for CPU-bound conversion |
| `--batch-size N` | `-b` | `50` | Files processed per async batch |
| `--semaphore N` | — | `20` | Max concurrent I/O operations |
| `--preserve-structure` | — | off | Mirror CHM folder hierarchy in `data/`; preserve relative links |
## Profiles
| Profile | Description |
| --------- | ---------------------------------------------------------------------------------------------------------------------- |
| `generic` | Minimal cleanup — works with any CHM file |
| `revit` | Strips Autodesk Revit help-viewer UI chrome (collapsible regions, feedback links, code-tab toolbars, boilerplate text) |
Custom profiles can be created programmatically:
```python
from chm_converter.config import ConversionConfig
from chm_converter.pipeline import process_chm_file
import asyncio
cfg = ConversionConfig(
classes_to_remove=["my-nav-bar", "site-footer"],
ids_to_remove=["cookie-banner"],
cleanup_patterns=[
(r"Rate this article.*?---", "---"),
],
)
asyncio.run(process_chm_file("docs.chm", "extracted", "output", cfg=cfg))
```
## AI Integration
The `core/` folder is designed for RAG and AI search pipelines:
- `file_index.json` — maps every file ID to its title, filename, and version
- `id_lookup.json` — lowercase-keyed with extracted keyword lists for full-text search
- `index.md` — human-readable alphabetical index with anchor links
## Troubleshooting
| Problem | Solution |
| ----------------------------------------------- | ------------------------------------------------------------------------------------------ |
| `7z not found` | Install 7-Zip and ensure it is on `PATH`; see Requirements above |
| Empty output / `No HTML files found` | CHM uses a nested folder layout — add `--preserve-structure` to enable recursive traversal |
| Revit 2025+ pages contain only a title, no body | Fixed in current version: `TopicContent` is no longer stripped from the Revit profile |
| Garbled CJK text | The tool auto-detects encoding via `chardet`; try `--profile generic` if issues persist |
| Memory errors on large CHM | Reduce `--workers` and `--batch-size` |
| Permission errors | Run the terminal with administrator / sudo privileges |
## License
MIT License
## Author
**Duong Tran Quang (DTDucas)**
baymax.contact@gmail.com
[github.com/DTDucas](https://github.com/DTDucas)
Author: [dtducas.com](https://dtducas.com)
### Contributors
- **Jiangxumin** — Chinese encoding support, cross-platform 7-Zip detection, memory-safe batch processing ([PR #11](https://github.com/DTDucas/chm-converter/pull/11))
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