Compositor

Open source alternative to Adobe Photoshop, Affinity Photo 2 and Pixelmator Pro

17.6K stars
MIT
Active this week
Last commit 7 days ago

Last verified Oct 21, 2026

Edit photos and composite images on a Mac with a Photoshop-compatible layer system, MIT license, and full Apple silicon performance.

Visit website GitHub17.6K

Read the full breakdownWho it is for, how it works, trade-offs, the quick start and the FAQ

who it's for

Who Compositor is for#

Designers compositing photos on Apple silicon Macs

Compositor's layer system, blend modes, adjustment layers, and layer effects cover the full standard compositing workflow. Photoshop keyboard shortcuts carry over directly, so a designer can move their existing muscle memory to a free, MIT-licensed tool without relearning the interface.

Skip if:

If your team works across macOS and Windows, Compositor does not run on Windows. If you need CMYK output or rely on Photoshop features beyond compositing and post-processing, gaps may require keeping Photoshop available.

Photographers doing post-processing and retouching

The Camera Raw filter covers light, color, curves, and geometry in a panel beside the canvas. Spot Healing Brush, Clone Stamp, and Content-Aware Fill handle retouching. Levels, Curves, Hue/Saturation, Exposure, and Gradient Map are available both as adjustment layers and as direct adjustments.

Skip if:

If your workflow centers on catalog management or batch processing a large library, Compositor is a per-image editor with no built-in catalog or batch-export feature.

Developers building AI image pipelines on macOS

The .comp project format is a folder of PNG layers and a manifest that AI agents and scripts can read and write directly. An open project updates live as the folder is modified, making Compositor scriptable in ways no commercial image editor supports natively.

Skip if:

If your AI pipeline targets Linux or needs to run on a server without a display, the .comp format can be assembled without Compositor's UI, but the app itself requires macOS 26 on Apple silicon.

Swift developers and open source contributors

The full Xcode project is available under MIT. Swift developers can add features, fix bugs, or port workflows directly in the codebase. The release script handles signing, notarization, and DMG packaging, lowering the barrier to shipping a modified build.

Skip if:

If you need a shipping image editor today and do not intend to build from source, downloading the pre-built release from GitHub Releases is the right path.

the problem

The problem it solves#

Adobe Photoshop requires an ongoing subscription to use. For Mac users who need professional image editing for compositing and post-processing, the cost is the primary friction.

Mac users doing this kind of work are left choosing between an ongoing subscription, a paid proprietary product like Affinity Photo 2, or learning a different editing paradigm. GIMP is free but its interface conventions differ enough from Photoshop's that switching means relearning keyboard shortcuts, the layer panel, and the muscle memory that Photoshop users have built over years.

how Compositor solves it

How it solves it#

Photoshop-compatible layer system

Layers and folders with Photoshop's full set of blend modes in Photoshop's order. Folder opacity dims everything inside it. Layer masks are paintable, fillable, invertable, blurrable, and featherable anywhere on the canvas, past the layer's own pixels. Adjustment layers include Hue/Saturation, Levels, Curves, Exposure, Gradient Map, Grain, Black and White, Color Balance, Invert, Gaussian Blur, Motion Blur, and Noise.

Camera Raw filter with full control panel

Applies a Camera Raw filter with controls for light, color, curves, color mixer, color grading, detail, optics, and geometry, displayed in a panel beside the canvas. Live previews apply within any active selection, so you can adjust a masked region without affecting the whole image.

PSD and PSB import with editable layers

Opens 8-bit RGB Photoshop files and keeps folders, masks, blend modes, fill shapes, and simple horizontal text editable rather than flattening them. A conversion report appears before anything is applied. Large PSD files too big to open have their layers cropped to the canvas instead of refusing to open.

Content-Aware Fill and Object selection

Content-Aware Fill removes objects from a photo and fills the gap by synthesizing surrounding pixels. It can also extend a canvas beyond its current edges. Object selection (part of the Magic tool, toggled with Tab) traces whatever you click, so isolating a subject does not require a freehand selection.

Non-destructive transform and GPU layer effects

Move, scale, rotate, and flip operations preserve the layer's full original resolution however small you make it. Layer effects (Stroke, Drop Shadow, Color Overlay, Inner Shadow, Outer Glow, Inner Glow) are rendered on the GPU and remain editable at any time without re-flattening the layer.

AI-agent-editable .comp project format

A .comp project is a folder of PNG layers and a manifest file. AI agents and scripts can build or modify projects by writing to that folder structure, and an open project in Compositor updates live as files change. The format specification is documented in the repository at docs/writing-comp-files.md.

strengths · trade-offs

Strengths and trade-offs#

Strengths

MIT license with no subscription or seat feeCompositor is MIT licensed, which means you can download, run, modify, and redistribute it with no cost, no subscription, and no usage limits. Compared to Photoshop's subscription model and Affinity Photo 2's paid license, there is no ongoing financial commitment to keep using the full tool.
Photoshop keyboard shortcuts and workflow parityCompositor ships with Photoshop-style keyboard shortcuts throughout, remappable in Edit > Keyboard Shortcuts, and replicates Photoshop-specific interaction patterns such as scrubbing a number's label to change its value. Existing Photoshop users can start working without relearning shortcuts or muscle memory.
Native Apple silicon performanceBuilt in Swift for Apple silicon, Compositor runs GPU-accelerated layer effects and high-quality downsampling natively. It does not run through Rosetta translation, so it gets the full chip performance and battery efficiency of an M-series Mac.
Open source and fully modifiableThe Xcode project is available to build, fork, and extend. A developer can add, remove, or change features directly in the Swift source rather than waiting for a paid vendor's roadmap. The app is signed and notarized and ships automatic updates.

Trade-offs

-macOS 26 on Apple silicon onlyCompositor requires macOS 26.0 or later on a Mac with Apple silicon. It does not run on Intel Macs, older macOS versions, Windows, or Linux. Teams with mixed hardware or cross-platform workflows cannot use it as a shared standard.
-New project with a short track recordThe repository was created in September 2026. The project is very early-stage with an unproven maintenance history. Features and the file format may change, and the issue tracker will likely surface gaps over time that a more mature tool would have addressed.
-No CMYK support for PSD importPSD and PSB import supports 8-bit RGB only. CMYK Photoshop files are not supported. Print workflows that rely on CMYK color mode will need to convert files before they can be opened in Compositor.

versus alternatives

Compositor vs alternatives#

Compositor vs Adobe Photoshop

Adobe Photoshop is the industry standard Compositor was built to replace for Mac users. The key differences are cost model and platform access.

Feature	Compositor	Adobe Photoshop
License	MIT (free)	Proprietary
Price model	Free	Subscription
Platform	macOS 26+ on Apple silicon	macOS and Windows
CMYK support	No	Yes
PSD compatibility	Imports 8-bit RGB	Native format
Photoshop shortcuts	Yes (remappable)	Yes

Compositor is the better choice for Apple silicon Mac users who want to stop paying a Photoshop subscription for compositing and post-processing work. Keyboard shortcuts carry over, the layer system replicates Photoshop's blend mode order, and PSD files open with editable layers. Adobe Photoshop remains the better choice for CMYK print work, Windows users, or anyone who needs features beyond compositing and post-processing, such as a video timeline, advanced type handling, or scripting with Photoshop Actions.

Compositor vs Affinity Photo 2

Affinity Photo 2 is a paid, proprietary image editor positioned as a Photoshop alternative on macOS, Windows, and iPad. Both tools target Photoshop users, but they differ on license, price, and platform coverage.

Feature	Compositor	Affinity Photo 2
License	MIT (free)	Proprietary
Price model	Free	One-time purchase
Source available	Yes	No
Platform	macOS 26+ on Apple silicon	macOS, Windows, iPad
CMYK support	No	Yes
AI-agent scripting	Yes (.comp format)	No

Compositor is the better choice when zero licensing cost and source availability matter, or when you need AI-agent scriptability via the .comp project format. Affinity Photo 2 is the better choice for cross-platform teams that include Windows users, iPad workflows, or work requiring CMYK color mode.

install · quick start

Quick start#

bash

Install Compositor via Homebrew or download the signed DMG from GitHub Releases.
```bash
brew install --cask robbietilton-compositor
```

tech stack · detected from GitHub

What it's built on#

Languages: CSwift

frequently asked

FAQ#

Is Compositor free to use?

Yes. Compositor is MIT licensed and available to download at no cost. There is no subscription, no free tier with paid features gated behind it, and no usage limit. You can use it for personal or commercial work without paying anything.

Does Compositor run on Intel Macs or Windows?

No. Compositor requires macOS 26.0 or later on a Mac with Apple silicon. Intel Macs and non-Apple platforms are not supported. If you need a cross-platform image editor, Compositor is not the right choice.

Can Compositor open Photoshop PSD files?

Yes, for 8-bit RGB PSD and PSB files. Folders, masks, blend modes, fill rectangles and ellipses, and simple horizontal text remain editable after import. CMYK files and complex vectors or vertical text are converted to pixels. A conversion report appears before any changes are applied.

What makes Compositor different from GIMP?

Compositor is built for Photoshop users who want familiar shortcuts and a workflow close to what they already know. It ships with Photoshop keyboard shortcuts remappable in Edit > Keyboard Shortcuts and replicates interaction patterns like label-scrubbing. GIMP uses its own interface conventions and workflow, which takes time to learn for anyone coming from Photoshop.

Can AI agents or scripts edit Compositor projects programmatically?

Yes. A .comp project is a folder of PNG layers and a manifest file. Any script or AI agent with file system access can write layers and update the manifest, and Compositor updates the open project live as files change. The format specification is documented at docs/writing-comp-files.md in the repository.

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Find open source alternatives to paid software

Compositor vs Adobe Photoshop

Adobe Photoshop is the industry standard Compositor was built to replace for Mac users. The key differences are cost model and platform access.

Feature	Compositor	Adobe Photoshop
License	MIT (free)	Proprietary
Price model	Free	Subscription
Platform	macOS 26+ on Apple silicon	macOS and Windows
CMYK support	No	Yes
PSD compatibility	Imports 8-bit RGB	Native format
Photoshop shortcuts	Yes (remappable)	Yes

Compositor vs Affinity Photo 2

Feature	Compositor	Affinity Photo 2
License	MIT (free)	Proprietary
Price model	Free	One-time purchase
Source available	Yes	No
Platform	macOS 26+ on Apple silicon	macOS, Windows, iPad
CMYK support	No	Yes
AI-agent scripting	Yes (.comp format)	No

Who Compositor is for#

Designers compositing photos on Apple silicon Macs

Skip if:

Photographers doing post-processing and retouching

Skip if:

Developers building AI image pipelines on macOS

Skip if:

Swift developers and open source contributors

Skip if:

The problem it solves#

How it solves it#

Photoshop-compatible layer system

Camera Raw filter with full control panel

PSD and PSB import with editable layers

Content-Aware Fill and Object selection

Non-destructive transform and GPU layer effects

AI-agent-editable .comp project format

Strengths and trade-offs#

Strengths

Trade-offs

Compositor vs alternatives#

Compositor vs Adobe Photoshop

Compositor vs Affinity Photo 2

Quick start#

What it's built on#

FAQ#

Similar open-source tools#

Open source tools in these categories#

Design & Creative

Product & Project Management

Find open source alternatives to paid software

Who Compositor is for#

Designers compositing photos on Apple silicon Macs

Skip if:

Photographers doing post-processing and retouching

Skip if:

Developers building AI image pipelines on macOS

Skip if:

Swift developers and open source contributors

Skip if:

The problem it solves#

How it solves it#

Photoshop-compatible layer system

Camera Raw filter with full control panel

PSD and PSB import with editable layers

Content-Aware Fill and Object selection

Non-destructive transform and GPU layer effects

AI-agent-editable .comp project format

Strengths and trade-offs#

Strengths

Trade-offs

Compositor vs alternatives#

Compositor vs Adobe Photoshop

Compositor vs Affinity Photo 2

Quick start#

What it's built on#

FAQ#

Similar open-source tools#

Open source tools in these categories#

Design & Creative

Product & Project Management

Find open source alternatives to paid software