Compositor README

The project's README from github.com/robbietilton/Compositor. As one markdown file: README.md.

Compositor

Adobe Photoshop costs too much and tools like GIMP don’t feel familiar enough for me to stay in flow. That’s why I built Compositor.

The goal was to create a full-featured image editor that is completely free and open source. I used to use Photoshop for compositing and post-processing, so Compositor is built around that workflow - with the tools needed to create a pixel-perfect final image.

Because it’s open source, you can download the Xcode project and add, remove, or modify any feature to fit your workflow.

Installation

Download

Get Compositor from robbietilton.com/compositor, or download the latest release directly from GitHub Releases.

Homebrew

brew install --cask robbietilton-compositor

Features

Layers

Layers and folders, with opacity and Photoshop's full set of blend modes in its order — a folder's opacity dims everything inside it
Layer masks: paint, fill, invert, blur and feather them anywhere on the canvas, past the layer's own pixels; link or unlink them to transform a mask on its own
Clipping masks and folder masks
Adjustment layers: Hue/Saturation, Levels, Curves, Exposure, Gradient Map, Grain, Black & White, Color Balance, Invert, Gaussian Blur, Motion Blur and Noise
Layer effects: Stroke, Drop Shadow, Color Overlay, Inner Shadow, Outer Glow and Inner Glow, rendered on the GPU and editable at any time
Merge Down, Merge Layers and Merge Group (⌘E)
Duplicate, rename inline, reorder and nest by drag and drop; Option-drag to duplicate; a right-click menu in the Layers panel
Copy and paste whole layers and folders (⌘C/⌘V with no selection), within a project or between projects, or drag them between projects

Transform

Non-destructive move, scale, rotate and flip — images keep their full resolution however small you make them
Free distort (⌘-drag a handle), with Shift to lock to an axis
Transform several layers, or a whole folder, together
Snapping to canvas and layer edges and centers, with guides
Exact values for position, size, scale and angle, stepped with the arrow keys
Flip Layer and Flip Canvas, horizontal and vertical

Selections

Rectangle and Ellipse Marquee, Freehand and Polygonal Lasso, and the Magic tool — Wand selects by color, Object traces whatever you click (Tab switches)
Select Subject, and Expand, Contract and Feather on any selection
Add to and subtract from selections, move the outline, or move and duplicate the pixels inside
Load a layer's pixels or a mask as a selection
Content-Aware Fill, which can also extend an image past its edges

Painting and retouching

Brush with size, hardness, opacity and smoothing, in Paint or Erase mode (B and E), and Shift for straight lines
Spot Healing Brush (content-aware)
Clone Stamp, aligned or not, sampling one layer or all of them
Blur tool, on pixels or masks
Gradient tool and Shape tool (rectangles, rounded rectangles, ellipses and lines), which stay editable rather than being rasterized
Type tool (T): inline multiline editing in draggable, resizable paragraph boxes; font, size, color, alignment and spacing in the tool header; transform text and use it as a clipping mask
Eyedropper and a full color picker

Adjustments and filters

Camera Raw filter: light, color, curves, color mixer, color grading, detail, optics and geometry, in a panel beside the canvas
Levels (with Auto), Curves, Hue/Saturation, Exposure, Gradient Map, Grain, Black & White, Color Balance and Invert
Gaussian Blur and Motion Blur that spread past a layer's edges
Add Noise, Vignette, Bloom / Glow, Dither, Scanlines, Tonal Contrast, Lens Correction and Remove Background
Live previews, limited to the selection when there is one
Last Filter (⌃⌘F) runs the last filter again with the same settings

Canvas and files

Multiple projects in tabs
Search Commands (⌘F): find every menu command and tool by name, as in Raycast or Obsidian, and run it with Return
Toggle Fullscreen (F): the canvas alone on black over the whole screen, with every panel put away; F or Esc brings them back
Rulers (⌘R), guides dragged from them, a layout grid with adjustable spacing and subdivisions, and Snap To for guides, grid, layers and document bounds
Crop with snapping, ratios including 3:4 and 9:16, and Option for symmetric cropping; with a selection, the crop starts at it
Canvas Size, Image Size and Trim
A Navigator minimap in the canvas's corner from 300% zoom: the whole document in small with a box around the view; click or drag to move there (View › Navigator)
Sharp high-quality downsampling when zoomed out, and a pixel grid when zoomed in
Import JPEG, PNG, HEIC, TIFF, WebP, SVG, camera RAW (with a develop step first) and Photoshop PSD and PSB (8-bit RGB; not CMYK). Photoshop folders, masks, blend modes, fill rectangles/ellipses, and simple horizontal text stay editable; other vectors and vertical text become pixels. A conversion report is shown before anything is applied.
Large documents: the memory budget scales with your Mac, and a Photoshop file too big to open has its layers cropped to the canvas instead
Export PNG (⇧⌘E), Export JPEG (⇧⌥⌘S), and Export As (⇧⌥⌘W) for PNG, JPEG or a one-page PDF at the print size, scaled if you like, with a live preview, JPEG quality and file size; Copy Merged
Keep working while a project saves
Photoshop-style keyboard shortcuts throughout, remappable in Edit > Keyboard Shortcuts
Drag a number's label to scrub its value, as in Photoshop
Automatic updates, signed and notarized

Works with AI agents

AI agents and scripts can build and edit projects directly: a .comp is a folder of PNG layers and a manifest, and an open project updates live as it's written. See Writing Compositor projects

Requirements

macOS 26.0 or later on a Mac with Apple silicon
Xcode 26 or later (to build from source)

Translations

Compositor is English only for now, and translation pull requests aren't being accepted. It's maintained by one person, every new string would need translating from then on, and translations in languages I don't read can't be reviewed. I'll revisit this once the app settles; until then, please don't open localization PRs.

Building

Open Compositor.xcodeproj and run the Compositor scheme.

Releasing

scripts/release.sh builds a Release version, signs it with Developer ID, notarizes and staples it, and packages it into dist/Compositor-<version>.dmg.

It needs, all kept outside this repository:

a Developer ID Application certificate in the login keychain
notarization credentials saved with xcrun notarytool store-credentials "compositor-notary" …
create-dmg (brew install create-dmg)

License

MIT — see LICENSE.

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What is this?

Compositor is a free and open-source, full-featured image editor for Mac, built as an alternative to Adobe Photoshop with a workflow centered on compositing and post-processing.

How do I get it running on my Mac?

Clone the repo, open Compositor.xcodeproj in Xcode, and run the Compositor scheme; once built, the app ships with automatic signed and notarized updates.

Can it fully open my existing Photoshop PSD files?

PSD import is limited to 8-bit RGB (not PSB or CMYK); layer folders, masks, a subset of blend modes and fill shapes stay editable, but text and other vectors get rasterized to pixels, and a conversion report is shown before the import is applied.

What makes Compositor's layer effects different from a typical filter?

Layer effects like Stroke, Drop Shadow, Color Overlay, Inner Shadow and Outer Glow are rendered on the GPU and stay editable at any time, instead of being baked permanently into the pixels.

Why did the author build Compositor instead of just using Photoshop or GIMP?

The author found Photoshop too expensive and GIMP unfamiliar enough to break their workflow, so they built a free, open-source editor modeled on the Photoshop compositing workflow they already knew.

Does it support non-destructive editing?

Yes - move, scale, rotate and flip transforms keep full resolution, shapes and gradients stay editable rather than rasterizing, and adjustment layers and layer effects can be changed at any time.

Are the keyboard shortcuts compatible with Photoshop?

Yes, Compositor uses Photoshop-style keyboard shortcuts throughout, and they can be remapped under Edit > Keyboard Shortcuts.

What are similar projects?

photocraft, PhotoGIMP, textream, photosuite, zulu, forel, dimble, travel-memory-sticker-card

Which topics is it in?

adobe, design-tool, photo-editor, image-manipulation, open-source-alternative, creative-tools, image-editing, xcode, native, apple, macos-app, graphics

Creator: robbietilton
Size: 11.1 MB
Stars: 17.3K
Updated: CommitOct 15 Releasev1.5.3Oct 15
Age: 1mo
Commits · 90 Days