⚡ JXLify

A Next-Generation Image Proxy & Origin Server in Rust
Serving JPEG XL (.jxl), AVIF (.avif), WebP (.webp), and Legacy Formats on the Fly with 100% In-Process Rust Codecs, Smart Content Negotiation, and Cache Acceleration.

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🌟 Overview

JXLify is a high-performance image proxy and origin web server written in Rust, designed as a modern, memory-safe, asynchronous evolution of webp_server_go.

JXLify sits as a middle-man in the loop between your users/CDN and your raw image assets. When a client requests an image (e.g. https://example.com/photos/landscape.jpg), JXLify dynamically negotiates client support using HTTP Accept headers and User-Agent heuristics, converts the image on the fly to the optimal format (JPEG XL, AVIF, or WebP), caches the generated asset and its metadata on disk, and serves it with instant response times and minimal CPU usage.

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🧭 Format Fallback Matrix & Negotiation Strategy

The Fallback Hierarchy

JXLify negotiates image formats using a 4-tier hierarchy:

$$\mathbf{JPEG\ XL\ (jxl)} ;\longrightarrow; \mathbf{AVIF\ (avif)} ;\longrightarrow; \mathbf{WebP\ (webp)} ;\longrightarrow; \mathbf{Original\ (JPEG/PNG/GIF/BMP)}$$

Targeted Single-Format Encoding (CPU-Efficient)

Instead of converting all formats simultaneously on every request (which wastes CPU and increases latency), JXLify determines the single highest-priority format the client supports and converts/serves only that format:

1. Client supports JPEG XL (image/jxl): Serves cached JXL or encodes to JXL.
2. Client supports AVIF (image/avif): Serves cached AVIF or encodes to AVIF.
3. Client supports WebP (image/webp): Serves cached WebP or encodes to WebP.
4. Client supports none of the above: Serves the original raw image (or resized raw image).

⚡ Redundant Conversion Skip

If the source raw image is already in the negotiated format (e.g. source is already photo.webp and client accepts WebP) and no resizing/cropping is requested, JXLify skips conversion entirely and serves the file directly with 0ms CPU overhead.

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🗄️ Unified Storage Layout & 2-Level Hash Sharding

All data is cleanly organized under the data/ directory:

• data/pics: Original source images.
• data/cache: Unified disk cache directory (safe to delete at any time):
  • data/cache/images/: Converted .jxl, .avif, .webp and resized variants (2-level sharded).
  • data/cache/metadata/: JSON metadata & BlurHash strings (2-level sharded).
  • data/cache/remote/: Downloaded upstream images in reverse proxy mode (2-level sharded).

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🗂️ Understanding & Configuring Storage Paths

In config.toml, only two paths are needed:

img_path = "./data/pics"     # Source images (local path or remote URL)
cache_path = "./data/cache"  # Unified cache (safe to delete anytime)

Config Key	Purpose	Typical Value	Description
img_path	Original Image Source	"./data/pics" or "https://cdn.example.com"	Directory (or upstream URL) containing raw source images.
cache_path	Unified Disk Cache	"./data/cache"	Cache directory for all generated data (images/, metadata/, remote/). Safe to delete at any time (rm -rf ./data/cache).

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How to Setup Storage

Mode 1: Local Origin Mode (Self-Hosted Images)

If your original image files are hosted on the local server or mounted volume:

1. Put your source images into ./data/pics/ (or any path like /var/www/uploads/).
2. Set img_path = "./data/pics".
3. Set cache_path = "./data/cache".
4. Requests to http://localhost:3333/photos/cat.jpg will resolve to ./data/pics/photos/cat.jpg and cache to ./data/cache/images/....

Mode 2: Remote Reverse-Proxy Mode (CDN / S3 / Cloud Storage)

If you want JXLify to sit in front of an existing remote image server:

1. Set img_path = "https://origin.example.com/assets".
2. Requests to http://localhost:3333/photos/cat.jpg will fetch https://origin.example.com/assets/photos/cat.jpg.
3. JXLify caches the raw file in data/cache/remote/, converts it to the client's optimal format, caches the result in data/cache/images/, and serves it instantly.

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Production Directory Sharding

In high-volume production environments with millions of images, flat directories cause severe filesystem inode lock contention and slow directory lookups. JXLify automatically implements 2-level hash sharding:

data/cache/images/local/
├── 8f/
│   └── 32/
│       ├── 8f32d4639f7f415f.jxl
│       ├── 8f32d4639f7f415f.avif
│       └── 8f32d4639f7f415f.webp
├── 01/
│   └── ee/
│       └── 01eef898821f07c6.webp

This distributes millions of files evenly across $256 \times 256 = 65,536$ subdirectories, maintaining $O(1)$ fast file lookups on all filesystems.

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🦀 100% In-Process Codecs & Transparency Preservation

No external CLI tools (FFmpeg / ImageMagick) are required. JXLify processes all formats entirely in-process:

1. Static Image Processing & Alpha Channels

• JPEG XL: In-process via jpegxl-rs (libjxl) and jxl-encoder. Preserves full alpha transparency (RGBA8/RGBA16).
• AVIF: Pure Rust via ravif / rav1e (the engine behind cavif-rs). Preserves full alpha transparency.
• WebP: In-process via webp and image / image-webp. Preserves alpha transparency.
• JPEG / PNG / BMP / GIF: Pure Rust decoding and encoding via image.

2. Animated GIF & WebP Processing

• Decoding: Multi-frame GIFs are parsed in-process via image::codecs::gif::GifDecoder, extracting all frames, transparent palettes, and frame delays.
• Encoding: Converted directly to animated WebP in-process using webp-animation, preserving frame rates, loop counts, and alpha transparency.
• Pass-through: Original animated GIF/WebP files are served untouched for legacy clients.

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⚡ Key Features

• 🚀 Asynchronous & Multi-Threaded: Built on Axum and Tokio with asynchronous I/O and Rayon thread pool for fast encoding.
• 🎯 Intelligent Content Negotiation: Evaluates Accept header MIME types and User-Agent heuristics (e.g. Safari 17+, iOS 17+, Firefox >= 93, Chrome).
• 🔄 On-The-Fly Conversion: Automatic conversion of jpg, png, gif, bmp, svg, heic, nef into jxl, avif, or webp.
• 🗄️ Persistent Disk Caching with Hash Sharding: Caches optimized images and metadata in CACHE_PATH with 2-level directory sharding.
• 🔒 In-Flight Deduplication Lock: Uses async lock registry (DashMap) to eliminate duplicate encoding when multiple concurrent requests hit the same uncached image.
• 🌐 Local Origin & Remote Proxy Modes: Can serve from local directory (IMG_PATH: "./data/pics") or act as a reverse proxy for remote CDNs (IMG_PATH: "https://origin.example.com").
• 📐 On-Demand Resizing & Smart Cropping: Supports query parameters ?width=300&height=200, ?max_width=800&max_height=600 with multiple crop algorithms.
• 🔍 Image Metadata Endpoint: Append ?meta=full to retrieve image dimensions, color profile, size, and BlurHash string.
• 🧹 Automatic Cache Cleaner: Periodically enforces MAX_CACHE_SIZE using LRU / modification time pruning.
• 📦 Prefetching: Multi-threaded batch scanner (--prefetch / --prefetch-foreground) to pre-warm the cache before production deployment.
• 📊 HTTP Caching & Metrics: Sends Vary: Accept, User-Agent, weak ETag, Cache-Control, and X-Compression-Rate.
• 🩺 Health Check: Built-in /healthz endpoint for Kubernetes and load balancer monitoring.

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🚀 Quick Start

Installation

Install via Cargo (Binary)

You can install the jxlify server binary directly from crates.io:

cargo install jxlify

Once installed, verify the installation by running:

jxlify --help

Use as a Library Dependency

Add jxlify to your project's Cargo.toml:

[dependencies]
jxlify = "0.1"

Or add it via the command line:

cargo add jxlify

Build from Source

git clone https://github.com/fokx/jxlify.git
cd jxlify
cargo build --release

The compiled binary will be located at target/release/jxlify.

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⚙️ Configuration Reference

Generate a default config.toml:

./target/release/jxlify --dump-config > config.toml

Full Configuration Table

Option	Type	Default	Description	Environment Override
host	String	"0.0.0.0"	IP address to bind (use 127.0.0.1 for localhost only, 0.0.0.0 for all interfaces).	JXLIFY_HOST
port	String/Int	"3333"	TCP port for the HTTP server.	JXLIFY_PORT
quality	Integer	80	Compression quality (1–100). 80 offers visually lossless quality; 100 triggers true lossless encoding for JXL and WebP.	JXLIFY_QUALITY
allowed_types	Array	["jpg", "png", ...]	Whitelist of allowed image extensions. Requests for other extensions return 400 Bad Request. Use ["*"] to allow all.	JXLIFY_ALLOWED_TYPES
convert_types	Array	["jxl", "avif", "webp"]	Enabled modern output formats. Order does not matter (fallback priority is always JXL -> AVIF -> WebP). Remove a format (e.g. ["webp"]) to disable it.	JXLIFY_CONVERT_TYPES
strip_metadata	Boolean	true	When true, strips EXIF, GPS coordinates, and camera profiles from output files to minimize size and protect privacy.	JXLIFY_STRIP_METADATA
img_path	String	"./data/pics"	Root directory or remote HTTP/HTTPS upstream URL for source images.	JXLIFY_IMG_PATH
cache_path	String	"./data/cache"	Unified cache directory for all generated data (images/, metadata/, remote/).	JXLIFY_CACHE_PATH
enable_extra_params	Boolean	false	When true, enables on-demand dynamic resizing via query parameters (?width=, ?height=, ?max_width=, ?max_height=).	JXLIFY_ENABLE_EXTRA_PARAMS
crop_interesting	String	"InterestingAttention"	Focal point algorithm for aspect-ratio crops. Options: InterestingAttention, InterestingEntropy, InterestingCentre, InterestingNone.	JXLIFY_EXTRA_PARAMS_CROP_INTERESTING
cache_ttl	Integer	2592000	Browser cache TTL in seconds (default 2592000 = 30 days). Sent in Cache-Control: max-age=....	JXLIFY_CACHE_TTL
max_cache_size	Integer	0	Maximum disk cache size in Megabytes (e.g. 10240 for 10 GB). 0 = unlimited. Background cleaner automatically removes oldest LRU files when exceeded.	JXLIFY_MAX_CACHE_SIZE
read_buffer_size	Integer	4096	Internal I/O read buffer size in bytes for streaming files.	JXLIFY_READ_BUFFER_SIZE
concurrency	Integer	262144	Maximum concurrent request worker pool size.	JXLIFY_CONCURRENCY
disable_keepalive	Boolean	false	Set to true to close TCP connection after each request (Connection: close).	JXLIFY_DISABLE_KEEPALIVE

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Detailed Setting Explanations

1. Image Quality (quality = 80)

• Controls lossy compression density across all encoders (1–100).
• 80 is the recommended default, providing ~70–85% file size reduction with zero visible artifacting.
• 100 activates lossless compression mode in libjxl (JPEG XL) and libwebp (WebP).

2. Format Whitelist & Target Formats

• allowed_types: Security control preventing arbitrary file serving. Only extensions in this list will be processed (e.g. jpg, jpeg, png, gif, bmp, svg, heic, nef, webp, avif, jxl).
• convert_types: Allows selectively disabling newer formats if desired. For example, setting convert_types = ["avif", "webp"] disables JXL conversion even if client supports it.

3. Dynamic Resizing & Smart Cropping (enable_extra_params = true)

When enabled, JXLify dynamically resizes images based on URL query parameters:

• GET /photo.jpg?width=400&height=300: Resizes and crops to exact 400x300 dimensions using the configured smart crop algorithm (crop_interesting).
• GET /photo.jpg?max_width=800&max_height=600: Proportionally fits image within bounding box while preserving original aspect ratio.

4. Cache Cleanup & Quotas (max_cache_size)

• If max_cache_size = 10240 (10 GB), a lightweight background cleaner runs every 60 seconds.
• If total cache size exceeds the limit, the cleaner automatically purges the oldest, least-recently-modified files (LRU policy) until cache size is within limits.
• Also cleans stale .tmp.* temporary files from interrupted writes.

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📖 CLI Usage

# Start server with default ./config.toml
./target/release/jxlify

# Specify custom config file
./target/release/jxlify --config /etc/jxlify/config.toml

# Prefetch all images in background while server runs
./target/release/jxlify --prefetch --jobs 8

# Prefetch all images in foreground and exit
./target/release/jxlify --prefetch-foreground --jobs 8

# Print version
./target/release/jxlify -V

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🐧 Running as a Daemon (Systemd Service)

A production-ready systemd unit file is provided at jxlify.service.

1. Standard System Installation

# 1. Install binary to /usr/bin/
sudo install -Dm755 target/release/jxlify /usr/bin/jxlify

# 2. Install default configuration to /etc/jxlify/
sudo install -Dm644 config.toml /etc/jxlify/config.toml

# 3. Install systemd service unit
sudo install -Dm644 jxlify.service /etc/systemd/system/jxlify.service

# 4. Reload systemd daemon
sudo systemctl daemon-reload

2. Enable & Start

# Start and enable JXLify on boot
sudo systemctl enable --now jxlify

# Check service status
sudo systemctl status jxlify

3. View Logs

# Stream live logs
journalctl -u jxlify -f

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📡 HTTP API & Headers

Requesting Images

# Request image (Safari 17+ will receive image/jxl, Chrome will receive image/avif, older browsers get image/webp or JPEG)
curl -i -H "Accept: image/jxl,image/avif,image/webp,image/*,*/*;q=0.8" http://localhost:3333/sample.jpg

# Request image with on-the-fly resizing
curl -i http://localhost:3333/sample.jpg?width=400&height=300

# Inspect metadata & BlurHash
curl -i http://localhost:3333/sample.jpg?meta=full

Response Headers Example

HTTP/1.1 200 OK
Content-Type: image/jxl
Content-Length: 42150
Vary: Accept, User-Agent
ETag: W/"a9b8c7d6e5"
Cache-Control: public, max-age=31536000, immutable
X-Original-Format: jpeg
X-Served-Format: jxl
X-Compression-Rate: 0.38
Server: JXLify

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📄 License

Licensed under the Apache License, Version 2.0 (LICENSE).