How masoc is built.

masoc is written in Swift, with one SwiftUI codebase for all three devices. On the Mac it is a native macOS app, not Mac Catalyst, with its own Settings window. iPad and Mac get a menu bar and keyboard shortcuts. masoc needs iOS 26, iPadOS 26 or macOS 26, and a Mac with Apple silicon.

The whole editor is one panel, the Deck. masoc looks at the space it has: where the window is narrow, the Deck lies under the photo; where there is room, it stands at the side. Liquid Glass sits on the controls only, never on your photo. More in how masoc is designed.

• Swift concurrency. Code runs on the main actor by default. The renderer is its own actor, and blocking work like Core ML gets a queue of its own, so it doesn’t hold up the interface.
• Observation and SwiftData. The interface follows state through @Observable, and your library lives in SwiftData.
• A non-destructive edit stack. Every edit is one Codable value, saved as JSON with the photo. The original file never changes. Each stack carries a version, so an older masoc never overwrites edits made by a newer one.

Swift files

~290

lines of Swift

60,000+

custom Metal kernels

30

bundled Core ML models

4

masoc renders on the GPU through one shared Metal context. The math happens in linear Display P3, a wider color space than sRGB, and in-between images keep 16-bit floating-point precision. While you drag, masoc renders a lighter preview. When you let go, the full-detail version takes its place. Exports go out as HEIC, JPEG or PNG, in Display P3, sRGB or Adobe RGB, and where memory is tight, big files render in strips.

RAW files are decoded by Apple’s RAW engine, Core Image’s CIRAWFilter. White balance is set right there, in true Kelvin, before any other edit. More about RAW in masoc.

Where built-in filters aren’t enough, 30 kernels written in Metal take over: the color mixer, hue shift and color grading in a single pass, noise reduction, sharpening, dehaze, grain, lens corrections, Log video and the blending of HDR and panorama merges.

Order changes the result. Retouching comes first, on the original, so a removed spot stays put when you crop. A look sits after camera calibration, as a creative layer on top. Grain and vignette come after the masks, so a mask never smooths the grain away. The frame comes last.

1. Retouch
2. Lens vignetting, fringing
3. Distortion, perspective, crop
4. Camera calibration
5. Look (LUT)
6. Exposure
7. White balance
8. Contrast, highlights, shadows
9. Saturation
10. Tone curve
11. Vibrance
12. Color mixer and grading
13. Dehaze
14. Noise reduction
15. Clarity, structure, texture
16. Sharpening
17. Glow
18. Background blur
19. Masks
20. Grain
21. Vignette
22. Censor
23. Frame

On RAW files, white balance and the base curve happen even earlier, in the decode. On JPEG, HEIC and other files, white balance shifts at step 7.

• Masks. Subject and background come from Apple’s Vision framework. The sky comes from two Core ML models working together: one traces the fine edges, the other confirms there is sky at all and fills the gaps.
• Depth and retouch. A depth model reads a single photo for background blur, and an inpainting model paints the fill when you remove something.
• Smart Edit. It uses Apple’s Foundation Models framework, the on-device model behind Apple Intelligence. The model fills in a typed plan, and masoc’s own code checks every value before it reaches a slider. Speech is transcribed on the device too. More about Smart Edit.

Why this matters for your photos: private by design.

• iCloud sync. CloudKit’s CKSyncEngine moves photos, videos and presets through your private iCloud database. It stays off until you turn it on.
• Share and export. A Share extension drops photos, presets and LUTs into an App Group inbox for masoc. On iPhone, exports show their progress in a Live Activity, and where the device allows GPU work in the background, they keep running after you leave the app.
• Video. AVFoundation reads and writes the clips, as HEVC 10-bit or H.264. Twelve Log profiles are decoded by a Metal kernel and graded like RAW. More about Log video.
• Merges. HDR brackets are aligned with Vision and saved as half-float OpenEXR. For panoramas, OpenCV finds how the photos line up and where the seams go. Warping and blending run in masoc’s own Metal kernels.

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