compositor-windows

A small, focused image editor for Windows: layers, masks, selections, brushes, adjustments and filters, with Photoshop-style tools and shortcuts and none of the bloat.

It is a Windows port of compositor-linux, which is itself a Qt 6 / C++20 port of the macOS app Compositor by Wonder Assembly LLC. All three share one document model and open the same .comp projects, so files move between them freely. The Mac sources under Compositor/ and Compositor.xcodeproj are kept in this tree as the reference the port is built against.

_{Filter > G'MIC: over 700 filters with their own controls and a live preview.}

Get it

There is no prebuilt Windows installer yet: build from source in an MSYS2 MINGW64 shell, as below, and run build-win/src/app/compositor-linux.exe.

On Linux and macOS the upstream compositor-linux releases carry a self-contained AppImage and an Apple Silicon app bundle; the same sources build here unchanged.

Open an image with File > Open or drop it on the window, and go.

What you get

• Layers, folders, blend modes, opacity, and layer masks
• Move, scale, rotate and distort without losing pixels
• Marquee, lasso and magic wand selections; content-aware fill
• Brush, eraser, spot healing, clone stamp, smudge, gradient and shape tools
• Levels, curves, hue/saturation, exposure, gradient map, grain, blurs, noise
• Remove Background with a local model, if you turn it on in Preferences
• Text layers in any installed font, editable until painted on
• Opens Photoshop PSD files with their layers, folders, masks and blend modes
• The G'MIC filter library (700+ filters) through Filter > G'MIC, when gmic is installed
• Multiple projects in tabs; PNG and JPEG export
• The keyboard shortcuts you already know

The full list is in docs/features.md.

Windows notes

The Windows port keeps the whole editor and its automation surface, and adds a few things the platform needs:

• HEIC/HEIF import. Qt ships no HEIC plugin on Windows, so HEIC/HEIF files are decoded through libheif when it is installed (-DCOMPOSITOR_WITH_LIBHEIF, on by default), falling back to a Qt plugin when the distribution provides one. See src/app/Heif.cpp.
• Automation over a named pipe. --rpc-socket name listens on \\.\pipe\name; the Python tools (tools/rpc_smoke.py, mcp/compositor_mcp.py) open the pipe directly, because CPython on Windows has no AF_UNIX. --headless still works, so the whole automation surface is available.
• No DBus autolaunch hang. Qt6DBus is linked in for the XDG portal colour scheme; on Windows, main() sets DBUS_SESSION_BUS_ADDRESS=disabled: when no bus is configured, so libdbus never spawns a dbus-daemon that outlives the process and holds a caller's stdout pipe open.

Remove Background

Off by default. Edit > Preferences > AI background removal downloads a segmentation model (from the rembg project) into your data folder and runs it on your machine. Nothing is uploaded anywhere.

Use it with an AI agent

The editor can be driven by Claude Code or any MCP client: open files, inspect and edit layers, run adjustments and filters, and look at the result.

claude mcp add compositor -- uv run /path/to/compositor-windows/mcp/compositor_mcp.py

Then ask for things like "open photo.jpg, remove the background, add a dark gradient behind it and export result.png". Details, the protocol and the full method list are in docs/automation.md.

Build on Windows

In an "MSYS2 MINGW64" shell:

pacman -S mingw-w64-x86_64-{gcc,cmake,ninja,qt6-base,qt6-svg,qt6-imageformats,libpng,opencv,libheif}
cmake -S . -B build-win -G Ninja -DCMAKE_BUILD_TYPE=RelWithDebInfo
cmake --build build-win -j
ctest --test-dir build-win --output-on-failure
./build-win/src/app/compositor-linux.exe

The root CMakeLists.txt sets _USE_MATH_DEFINES, NOMINMAX and WIN32_LEAN_AND_MEAN for MinGW (its <math.h> hides M_PI otherwise, and <windows.h> defines min/max as macros). OpenCV comes from MSYS2 (mingw-w64-x86_64-opencv) and supplies the DNN module Remove Background needs.

Build on Linux and macOS

Arch / Manjaro:

sudo pacman -S cmake ninja qt6-base qt6-svg qt6-wayland qt6-imageformats libpng opencv

Ubuntu 24.04:

sudo apt install cmake ninja-build qt6-base-dev qt6-svg-dev qt6-wayland qt6-image-formats-plugins libpng-dev libgl1-mesa-dev libopencv-dev

macOS (Homebrew), where the build produces an app bundle instead:

brew install cmake ninja qt libpng opencv pkg-config
cmake -S . -B build -G Ninja -DCMAKE_BUILD_TYPE=Release -DCMAKE_PREFIX_PATH="$(brew --prefix qt)"
cmake --build build -j && open build/src/app/compositor-linux.app

Then, on Linux:

cmake -S . -B build -G Ninja -DCMAKE_BUILD_TYPE=Release
cmake --build build -j
./build/src/app/compositor-linux

docs/linux-port.md has the build options, command-line flags, the source layout, how releases are made and the keyboard shortcuts. docs/linux-port-architecture.md explains how the port relates to the Mac sources, which stay in this tree untouched.

Credits and license

This project stands on two open-source projects, and could not exist without them:

• Compositor — the original macOS image editor by Wonder Assembly LLC, whose document model, compositor, pixel routines and .comp format this port reproduces. Its README is kept at docs/upstream-README.md.
• compositor-linux — the Qt 6 port this Windows port is built on; the portable C++ core, the Qt front end and the build system all come from there.

Both are MIT licensed. This project is MIT as well, see LICENSE. It also bundles nlohmann/json (MIT) and the Lucide icons (ISC).