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ambiligth/README.md
2026-03-16 17:31:21 +01:00

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# Ambiligth
Ambiligth is a highly optimized, cross-platform Rust application that captures your screen's dominant color in real-time and synchronizes it with your smart lights via Home Assistant. It acts as a software-based "Ambilight" for your monitor, creating an immersive viewing experience.
## Features
- **Cross-Platform Screen Capture:**
- Linux (via `grim-rs`)
- macOS (via `CoreGraphics`)
- Windows (via `GDI` / `BitBlt`)
- **Advanced Color Processing:** Uses `okmain` (Oklab color space) to accurately and efficiently extract the perceptual dominant color of the screen.
- **Smart Image Diffing:** Uses `image-compare` (MSSIM simple algorithm) to perceptually compare screen frames. It only sends updates to Home Assistant if the screen content has changed significantly, preventing API spam and light flickering.
- **RGBW/RGBWW Support:** Intelligently preserves brightness and white channels for advanced smart lights, updating only the color values.
- **Smooth Transitions & Filtering:** Built-in exponential smoothing and configurable Home Assistant transition times.
- **Auto-Restore:** Optionally takes a snapshot of your lights' state on startup and restores them to their original colors when you exit the program.
## Prerequisites
- Rust (cargo)
- A running Home Assistant instance with a Long-Lived Access Token.
- Color-capable smart lights integrated into Home Assistant.
- *Optional:* `nix` (if you are using the provided Nix flake environment).
## Configuration
Ambiligth is configured via a `config.toml` file in the root of the project, or via environment variables (e.g., `HA_URL`, `HA_TOKEN`).
Create a `config.toml` file with the following options:
```toml
# Your Home Assistant URL (default: "http://localhost:8123")
ha_url = "http://192.168.1.100:8123"
# Your Long-Lived Access Token (Required)
ha_token = "ey..."
# Target Frames Per Second for light updates (default: 15)
# This is the MAXIMUM rate - lights only update when color actually changes
target_fps = 15
# Color smoothing factor from 0.0 to 1.0 (default: 0.0)
# Higher values mean slower, smoother color transitions.
smoothing = 0.5
# Time in seconds for the lights to transition to the new color (default: 0.5)
transition = 0.5
# Minimum perceptual difference percentage to trigger an update (default: 1.0)
# Increase this if lights are flickering on mostly static screens.
min_diff_percent = 2.0
# Restore lights to their original state on exit (default: true)
restore_on_exit = true
# List of specific light entity IDs to control.
# If left empty, it will auto-detect all color-capable lights.
lights = [
"light.monitor_backlight",
"light.desk_strip"
]
```
## Running the Application
Because screen capture and image processing are highly CPU-intensive, **you must run this application in release mode** to achieve real-time performance and avoid high CPU usage.
```bash
# Standard cargo run
cargo run --release
# If you are using the Nix dev shell
nix develop -c cargo run --release
```
## How It Works
1. **Capture:** Takes a fast, SIMD-optimized screenshot using platform-native APIs.
2. **Diff:** Compares the new screenshot against the previous one using Structural Similarity (MSSIM). If the difference is below `min_diff_percent`, it skips the update.
3. **Analyze:** Calculates the dominant color of the current frame using the Oklab color space.
4. **Smooth:** Blends the new dominant color with the previous one based on the `smoothing` factor.
5. **Update:** Constructs a highly specific JSON payload for Home Assistant, ensuring white channels and brightness are preserved, and sends it asynchronously via `reqwest`.
# TODO: Parallel Event Loop Restructuring (COMPLETED)
This architecture has been implemented. See `src/eventloop.rs` for details.
## Architecture Overview
```
┌─────────────────────────────────────────────────────────────┐
│ Shared State │
│ │
│ current_screenshot ← Latest captured (screenshot loop) │
│ active_screenshot ← Screenshot that produced target_color│
│ target_color ← Color calculated from active_screenshot│
│ active_color ← Smoothed color sent to lights │
└─────────────────────────────────────────────────────────────┘
Data Flow:
Screenshot Loop (screenshot_fps) Color Calc (on-demand)
│ │
▼ ▼
[current_screenshot] [target_color]
│ │
│ diff(current, active) │
│ > min_diff_percent? │
▼ │
[active_screenshot] ◄───────────────────────┘
│ │
│ Smoothing Loop (target_fps)│
│ │ │
│ ▼ │
│ [active_color] ◄─────────┘
│ │
▼ ▼
Light Update (parallel to all lights)
```
## Implementation Tasks
### Phase 1: Settings Update (`settings.rs`)
- Add `screenshot_fps` config option (default: 3)
- Remove `transition` option (smoothing handles transitions)
### Phase 2: Create Shared State (`state.rs`)
```rust
pub struct AppState {
pub current_screenshot: RwLock<Option<Arc<Screenshot>>>,
pub active_screenshot: RwLock<Option<Arc<Screenshot>>>,
pub target_color: RwLock<Option<Rgb<f32>>>,
pub active_color: RwLock<Rgb<f32>>,
}
```
### Phase 3: Parallel Event Loop (`eventloop.rs`)
**Thread 1 - Screenshot Loop** (std::thread, runs at `screenshot_fps`)
- Capture screenshot → store in `current_screenshot`
- Compare `current_screenshot` vs `active_screenshot`
- If diff > `min_diff_percent`:
- Copy `current_screenshot``active_screenshot`
- Spawn color calc task
**On-demand - Color Calculation** (tokio::spawn)
- Calculate dominant color from `active_screenshot`
- Update `target_color`
**Thread 2 - Smoothing & Light Update** (tokio, runs at `target_fps`)
- Lerp `active_color` toward `target_color` using `smoothing` factor
- Send `active_color` to all lights **in parallel**
### Phase 4: Parallel Light Updates (`homeassistant.rs`)
- Refactor `set_lights_color` to update single light, return future
- Create `set_lights_color_parallel` using `futures::future::join_all`
## Concurrency Strategy
| Resource | Lock Type | Writer | Readers |
|---------------------|-----------|---------------------|----------------------------|
| current_screenshot | RwLock | Screenshot loop | Diff check |
| active_screenshot | RwLock | Screenshot loop | Color calc |
| target_color | RwLock | Color calc task | Smoothing loop |
| active_color | RwLock | Smoothing loop | Light update |
Each field has a single writer - no complex synchronization needed.
## File Changes Summary
| File | Changes |
|-------------------|----------------------------------------------|
| `settings.rs` | Add `screenshot_fps`, remove `transition` |
| `state.rs` | **New** - Shared state struct |
| `eventloop.rs` | **Rewrite** - Multi-threaded architecture |
| `homeassistant.rs`| Add parallel light update method |
| `main.rs` | Wire up new state, pass to eventloop |