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Picaius

A fast, offline-first photo editor for iPhone and iPad.

iOS · MVP Swift · SwiftUI Metal Core ML

Overview

Picaius is a layer-based mobile photo editor for iPhone and iPad, available at picai.us. It's built offline-first — the core editing pipeline runs entirely on-device, with no server required. The architecture is GPU-first: layers are composited through Metal rather than stacked as image views.

The project is currently an MVP.

What it does

  • Layer-based editing with Metal-accelerated GPU compositing
  • Real-time preview driven by DisplayLink (60 / 120 fps)
  • On-device background removal — uses iOS 17's VNGenerateForegroundInstanceMaskRequest, with a DeepLabV3 fallback on iOS 16
  • Perspective and warp transforms
  • Brush tools and text layers
  • Undo / redo with a command pattern (up to 50 steps)
  • Export to Photos
  • Custom .pxproj bundle format for saving projects
  • Face and object detection via the Vision framework

How it's built

  • Swift and SwiftUI, targeting iOS 16+
  • Metal for GPU rendering (MTLTexture, MTLRenderCommandEncoder)
  • Core Image (CIContext) and the Vision framework for image processing
  • Core ML for on-device inference
  • RevenueCat for the free tier and optional paid features
  • Companion web / API on Cloudflare Workers (Wrangler v4, TypeScript)