A local-first desktop app for managing and inverting film negative scans. Built with Tauri + SvelteKit. All data stays on your machine — no backend, no login, no cloud.

• Point the app at a directory of scans; it builds a Roll with auto-generated thumbnails (via a native Rust/Tauri worker pool)
• Browse frames in a filmstrip grid with virtual scrolling; prefetches neighbours to eliminate flicker
• Inspect EXIF metadata (aperture, shutter, ISO, film simulation, etc.) in a collapsible panel
• RGB histogram per frame
• Inversion (NegPy-backed pipeline): normalise → invert → colour matrix → tone/RGB curves → gamma encode
  • Real-time curves editor (drag control points, monotone cubic spline interpolation)
  • White balance controls
  • Per-channel exposure compensation
  • Roll-level defaults with per-frame overrides; originals never written
  • Undo / redo
  • Keyboard shortcuts for common controls
• Export developed frames
• Light / dark theme

• Tauri 2 (Rust backend) + SvelteKit 2 + Svelte 5 (runes mode) + TypeScript (strict: true)
• Tailwind CSS v4 with semantic @theme design tokens
• IndexedDB for roll/frame metadata + edit parameters
• OPFS for cached thumbnails and previews
• File System Access API for read-only access to scan directories
• Native Rust thumbnail generation (image crate, opt-level 3 in debug)

bun install
bun run dev          # Vite dev server on :5173 (browser-only mode)

For the full Tauri desktop app, install the Tauri prerequisites then:

bunx tauri dev

bun run dev          # Vite dev server
bun run build        # production web build
bun run preview      # preview production build

bun run check        # svelte-check + tsc (authoritative — 0 errors required)
bun run check:watch  # watch mode

bun run test         # run all tests (browser + server projects)
bun run test:unit    # vitest interactive mode

# single file
bunx vitest run src/lib/db/idb.test.ts

# by name (substring match)
bunx vitest run --reporter=verbose -t "createRoll"

# server project only (pure TS/JS, Node)
bunx vitest run --project server

# browser project only (requires Playwright / Chromium)
bunx vitest run --project client

src-tauri/          # Rust/Tauri backend (thumbnail generation, file I/O)
src/
  lib/
    types.ts        # domain types + resolveEdit()
    db/
      idb.ts        # low-level IndexedDB wrapper
      rolls.ts      # high-level roll operations
    fs/
      directory.ts  # File System Access API
      opfs.ts       # OPFS thumb/preview cache
    image/
      pipeline.ts   # inversion render pipeline
      thumbgen.ts   # OffscreenCanvas → JPEG → OPFS
      thumb-queue.ts / thumb.worker.ts  # worker pool
      curves.ts     # monotone cubic spline → 256-entry LUT
    components/
      CurvesEditor.svelte
      RgbHistogram.svelte
      ExifPanel.svelte
      InversionControls.svelte
      WhiteBalanceControls.svelte
      FrameThumb.svelte / FrameMetaPanel.svelte
      VirtualGrid.svelte
      ...
  routes/
    +page.svelte            # / — roll library
    library/                # library view
    roll/[id]/
      +page.svelte          # filmstrip grid + metadata panel
    raw/                    # raw/inversion editor

The in-editor LSP may report stale false-positive errors (known cache artefact). Always use bun run check as the ground truth — if it reports 0 errors the code is correct.