- Overview
- Key Features
- Technical Details
- Supported Image Formats
- PSD / PSB Decoding Model
- Keyboard Shortcuts & Controls
- Dependencies
- Installation
- Configuration & Data Files (UNIX specific)
Lyra is a high-performance, minimalist image viewer designed for speed, fluid navigation, and precision. It handles modern and professional image formats without the overhead of full editing suites or Electron-based tools. Built for anyone who relies on images as a core resource in their workflow:
- 2D/3D artists and game developers browsing texture maps and baked assets
- Photographers reviewing large batches of exports
- Developers inspecting UI assets, icons, and generated output
- And ordinary advanced users
- Fast navigation through large directories of images or texture assets.
- SVG support for previewing scalable vector assets.
- Adjustable background modes to improve visibility of transparent images
- Sampling toggle, useful for pixel-perfect graphics or UI assets.
- EXIF metadata display for viewing embedded image information.
- Zoom-to-cursor and panning for intuitive inspection at any scale.
- Reasonable support for modern image formats, with limited support for older formats that refuse to die.
Lyra is built on .NET 9 with SDL3 for windowing and input, and SkiaSharp for hardware-accelerated rendering via OpenGL or Metal. It is not an Electron app - there is no embedded browser, no web runtime, and no hidden resource overhead (and definitely no AI client). The architecture is designed around fast, non-blocking image loading:
- Decoded images are cached and adjacent files are preloaded in the background, so navigation feels instant even in large directories.
- Large PSD/PSB files use streaming and tiled decoding to avoid loading entire documents into memory - tested with files exceeding 3 GB.
Lyra integrates lightweight native interop wrappers for HDR and EXR decoding, and delegates format-specific work to focused libraries rather than bundling large native dependencies. System libraries like libheif, OpenJPEG and OpenEXR are expected from the package manager (e.g. Homebrew). Originally built for workflows involving texture maps, HDRIs, and assets exported from tools like Blender and Quixel Bridge - but the design generalizes well to any image-heavy workflow.
Developer note: Lyra is designed and written simultaneously. As a result, parts of the code reflect iterative exploration rather than a fully pre-planned architecture. Refactoring is ongoing wherever it improves clarity or maintainability.
| Format | Description | Extensions |
|---|---|---|
| PNG | Lossless raster image format with optional alpha | .png |
| JPEG / JFIF | Lossy raster image format (JPEG family) | .jpg .jpeg .jif .jfif |
| TIFF | High-precision raster image container | .tif .tiff |
| Targa | Raster image format with optional alpha | .tga |
| BMP | Uncompressed bitmap image format | .bmp |
| Format | Description | Extensions |
|---|---|---|
| WebP | Compressed raster image format with optional alpha | .webp |
| HEIF / HEIC | High-efficiency image container format (HEVC-based) | .heif .heic |
| AVIF | High-efficiency image format based on AV1 | .avif |
| Format | Description | Extensions |
|---|---|---|
| OpenEXR | High-dynamic range, multi-channel raster format | .exr |
| Radiance HDR | High-dynamic range RGBE format | .hdr |
| Format | Description | Extensions |
|---|---|---|
.dds |
||
.ktx .ktx2 |
| Format | Description | Extensions | Notes |
|---|---|---|---|
| SVG | Scalable Vector Graphics | .svg |
|
| Photoshop | Adobe Photoshop document | .psd .psb |
See PSD / PSB Decoding Model section below |
| Format | Description | Extensions | Notes |
|---|---|---|---|
| ICO | Icon container format | .ico |
|
.icns |
|||
| JPEG 2000 | Wavelet-based image format | .jp2 .jpg2.j2k .j2c .jpc |
Lyra supports single-image JPEG 2000 files. Multi-image, animated, or compound JPEG 2000 formats (JPX, JPM, MJ2, JPIP) are intentionally NOT supported. |
Note: Crossed-out formats are not implemented yet.
Lyra currently focuses on decoding the flattened Image Data section of Photoshop files, rather than individual layers. This design choice prioritizes performance and fast previewing.
This is explicitly documented because the Image Data section is not strictly mandatory in the PSD specification and, in some edge cases, may be missing or may not fully represent the document as it appears when opened in Photoshop.
Adobe Photoshop File Format Specification
| Color Mode | Channels | Lyra Support |
|---|---|---|
| Bitmap | 1 (1-bit) | Planned |
| Grayscale | 1 | Full |
| Duotone / Tritone / Quadtone | 1 + inks | In progress |
| Indexed | 1 + palette | Full |
| RGB | 3 | Full |
| CMYK | 4 | Full |
| Lab | 3 | Planned |
| Multichannel | N | Planned |
Lyra fully supports PSB (Photoshop Big Document Format) files.
- Successfully tested with ~3 GB PSB files
- Uses streaming / tiled decoding internally where possible to avoid loading entire images eagerly
Lyra honors embedded ICC color profiles whenever they are present. If a PSD / PSB document does not contain an embedded profile - most notably in CMYK color modes - Lyra falls back to the system’s default color profile to produce a usable result.
Without an explicit ICC profile, CMYK data has no well-defined color meaning. In such cases, different viewers may interpret the same document very differently, sometimes resulting in severely distorted or inverted-looking colors.
Lyra’s fallback behavior is intended to be predictable and standards-compliant rather than attempting heuristic or hard-coded CMYK assumptions.
Developer note: During development, Lyra was tested against several large CMYK PSB files from the NASA public image archive. These documents did not contain embedded ICC profiles and produced drastically different results across common image viewers - ranging from heavily shifted colors to near-inverted appearances.
This behavior is not a defect of the files themselves, but a direct consequence of CMYK data being interpreted without a defined color profile.
The PSD decoder is intentionally structured to allow future expansion.
| Key | Action |
|---|---|
← → |
Previous / Next image |
Home End |
First / Last image |
+ - |
Zoom in / Zoom out |
Mouse Wheel |
Zoom at cursor position |
Middle Mouse Button |
Customizable (see app-settings.toml) |
0 |
Toggle Fit to Screen / Original Size |
S |
Toggle sampling mode |
F |
Toggle fullscreen |
B |
Toggle background mode |
I |
Toggle image information overlay |
H |
Toggle help bar |
Return |
Reveal image or directory in native file explorer |
Esc |
Exit application |
| Key | Action |
|---|---|
⌘ ← ⌘ → |
First / Last image |
⌥ ← ⌥ → |
First / Last image within the directory |
| Context | How Lyra interprets it | Make a collection from files around | Recursion |
|---|---|---|---|
| Single file | Anchor (Open / Open With / Double-click) | Yes | No |
| Multiple files (same directory) | Selection | No | No |
| Single directory | Directory collection | No | Yes |
| Multiple directories | Multi-directory selection | No | Yes |
| Mixed files from different directories | Multi-directory selection | No | No |
Recursion applies only when directories are explicitly dropped. Opening or dropping files never implicitly expands into subdirectories.
Developer note: Lyra intentionally favors context-aware navigation. Opening a single image always implies “show me this image in relation to its neighbors”, not isolation.
| Library | Purpose | License | Repository |
|---|---|---|---|
| SDL3-CS | Core graphics, input, and windowing | zlib | github |
| SkiaSharp | Hardware-accelerated 2D rendering | BSD-3-Clause | github |
| Svg.Skia | SVG parsing and rendering | MIT | github |
| SixLabors.ImageSharp | Support for TGA, TIFF, and legacy formats | Apache 2.0 | github |
| LibHeifSharp | HEIF / HEIC image decoding | LGPL-3.0 | github |
| OpenEXR | High-dynamic-range OpenEXR (.exr) decoding | BSD-3-Clause | github |
| rgbe | Radiance HDR (.hdr) image decoding | Public Domain | webpage |
| OpenJPEG | JPEG 2000 still-image decoding | BSD-2-Clause | github |
| Unicolour | Color space conversions & perceptual color math (used in PSD decoding) | MIT | github |
| MetadataExtractor | EXIF metadata extraction | Apache 2.0 | github |
Lyra Viewer is distributed via Homebrew on macOS.
brew tap lyra-viewer/lyra
brew install --cask lyra-viewerNot available yet.
Lyra stores configuration and runtime data in standard XDG-compliant locations.
~/.config/lyra-viewer/
| File | Description |
|---|---|
app-settings.toml |
Application settings: renderer, window state, middle mouse button function, text sizes... |
ui-settings.toml |
UI state - saved automatically on exit |
~/.local/share/lyra-viewer/
| File | Description |
|---|---|
log.txt |
Application log output |
load-time-data.toml |
Recorded decode times per format, used to estimate loading progress |
If any configuration file is missing or malformed, Lyra falls back to built-in defaults and recreates the file on next save. Deleting everything under these directories is always safe - Lyra will start fresh with default settings.
