dvdstelt / Composa

# Composa
A layer-based image editor for compositing and retouching, with Photoshop-style tools and shortcuts. It is a from-scratch implementation of Compositor, Robbie Tilton's free and open-source macOS app.
https://github.com/user-attachments/assets/e215c376-2bb3-44d2-af26-3117d2c70348
The macOS app is written in Swift on top of AppKit, SwiftUI, CoreImage, Metal and Vision, so it cannot be compiled for anything else. Composa rebuilds the same editor from scratch in C# with .NET 10, Avalonia and SkiaSharp, which run on Linux, Windows and macOS alike.
Composa is developed on Linux, on X11 and Wayland (through XWayland), and that is where it gets the most use. Windows builds are published too and the full test suite runs on Windows for every change, but the Windows version is newer and has seen far less real use. A macOS build is planned.
## Features
### Layers
- Layers and folders with 24 blend modes, grouped in the menu as Photoshop groups them, and opacity
- Layer effects: Stroke (outside or inside), Drop Shadow, Outer Glow, Inner Glow, Color Overlay and Inner Shadow, each switchable, editable with a live preview and copied between layers by Alt-dragging
- Layer masks on layers, folders and adjustment layers: paint, fill, gradient, invert, blur, apply, disable
- Clipping masks (Alt-click a layer, or Ctrl+Alt+G)
- Adjustment layers: Hue/Saturation, Levels, Curves, Exposure, Gradient Map, Color Lookup, Grain, Brightness/Contrast, Black & White, Color Balance, Invert, and the live Gaussian Blur, Motion Blur and Add Noise, which work on everything beneath them
- Merge Down, Merge Layers, Merge Group (Ctrl+E) and Flatten Image
- Duplicate (several at once, stacked together above the topmost), rename inline, reorder and nest by drag and drop; Alt-drag to duplicate
- Copy and paste whole layers, folders and adjustments included, within a project or into another tab, where they arrive centered; a right-click menu on every row for the layer, its folder and its mask
- Swipe down the eye column to show or hide many layers; Alt-click an eye to solo a layer
### Transform
- Non-destructive move, scale, rotate and flip: images keep their full resolution however small you make them
- Free distort by Ctrl-dragging a corner; the handles follow the corners, which keep distorting once the layer is distorted, and a corner dragged past the opposite edge folds the layer over itself
- Ctrl-drag moves the current layer with any tool active, as Photoshop's temporary Move tool does
- Auto Select picks the layer under the pointer, including one stacked on a selected background that covers the canvas; turn it off to drag the current layer from anywhere (Ctrl-click still picks)
- Transform several layers, or a whole folder, together
- Snapping to canvas and layer edges and centers, with guides
- Exact values for position, size and angle; arrow keys nudge (Shift for 10 px)
- Live shape layers (rectangle, rounded rectangle, ellipse, line) that are redrawn sharp when scaled
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