Transformers

Upload a file → pick a target format → download the converted output. Works via web UI or JSON API.

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Features

• Image, video, audio, and PDF conversions (via ffmpeg & poppler).
• Safe uploads with size cap (50 MB) and MIME sniffing.
• Extension ↔ MIME validation, path sanitization, and strict static serving.
• Concurrency gate (3 concurrent jobs) + 150s conversion timeout.
• Security headers, request ID (X-Request-ID), and graceful shutdown.
• JSON or HTML responses (auto‑select via Accept header).

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Requirements

Install the external tools first:

• ffmpeg (images / audio / video)
• poppler (for PDF → image/text via pdftoppm / pdftotext)

macOS (Homebrew):

brew install ffmpeg poppler

Linux (Debian/Ubuntu):

sudo apt-get update && sudo apt-get install -y ffmpeg poppler-utils

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Run locally

go run .
# Server will start at http://localhost:3030

Static assets:

• UI: templates/index.html, templates/select_format.html
• Uploaded files: uploads/
• Converted files: converted/ (also served at /converted/…)

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Supported conversions

Images

• jpeg ↔ png ↔ webp ↔ bmp ↔ gif
• tiff → jpg/png
• gif → mp4/webm (animated GIF → video)

Video

• mp4 ↔ webm, mp4/webm → gif, any → mp3

Audio

• mp3 ↔ wav ↔ ogg ↔ flac; aac/m4a ↔ mp3/wav

Documents

• pdf → png/jpg/txt

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Web UI

Open http://localhost:3030

1. Upload a file
2. Choose a target format (only valid options shown)
3. Download the converted file

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JSON API

The server auto‑detects Accept: application/json and returns JSON.

1) Upload

POST /upload (multipart/form-data)

• Field: file — the file to upload

curl -H "Accept: application/json" \
  -F [email protected] \
  http://localhost:3030/upload

Response

{
  "filename": "1730112345678_ab12cd_example.mp4",
  "original": "example.mp4",
  "formats": ["WEBM","AVI","MOV","GIF","MP3"]
}

2) Convert

POST /convert (application/x-www-form-urlencoded or JSON)

• Params:
  • filename — server‑side stored name from /upload
  • original — original filename (used to suggest download name)
  • format — target extension (e.g., webm, mp3, png)

curl -H "Accept: application/json" \
  -X POST http://localhost:3030/convert \
  -d "filename=1730112345678_ab12cd_example.mp4" \
  -d "original=example.mp4" \
  -d "format=webm"

Response

{
  "download": "/download?file=1730112345678_ab12cd_example.webm&name=example.webm",
  "downloadName": "example.webm"
}

3) Download

GET /download?file=<stored>&name=<suggested>

Supports HEAD. Sets immutable caching & Content-Disposition for attachment.

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Safety & limits

• Upload limit: 50 MB (maxUploadSize)
• Conversion timeout: 150 s (conversionTimeout)
• Concurrency: 3 parallel conversions (maxConcurrentConversions)
• Security headers: CSP, X-Content-Type-Options, X-Frame-Options, Referrer-Policy, Permissions-Policy
• Request ID: every response includes X-Request-ID

Adjust these in the const block in main.go if needed.

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Project structure

.
├─ templates/
│  ├─ index.html
│  └─ select_format.html
├─ static/                # optional CSS/JS
├─ uploads/               # runtime (gitignored)
├─ converted/             # runtime (gitignored)
└─ main.go