Photo Animator
A Windows utility that scans a folder of JPEG frames and plays them back with scrubbing and keyboard shortcuts.
Features
- Folder scan for
.jpg/.jpeg, alphabetically sorted with lazy decode to keep startup fast.
- Playback controller with drop-frame math (elapsed-time driven), FPS selection (6-60), scrubbing slider, keyboard shortcuts, elapsed mm:ss:ff clock, and live dropped-frame counter.
- Auto-play kicks off as soon as a folder finishes preloading; controls stay disabled during preload to avoid interruptions.
- Double-buffered image surface to reduce flicker during swaps plus a memory-friendly cache that caps decoded frames to 1920x1080.
- Manual reload preserves FPS and attempts to restore state; a collapsible “Recent folders” tray keeps the last 6 folders handy and persists the last folder to seed the Open dialog.
- Help overlay (button or F1) lists the keyboard controls inline.
Keyboard Shortcuts
| Key |
Action |
| Space |
Play/Pause toggle |
| Left Arrow |
Previous frame |
| Right Arrow |
Next frame |
| Home |
Rewind to first frame |
| R |
Reload folder (re-scan frames) |
| F1 |
Show help overlay |
| Esc |
Close help overlay |
All shortcuts require the main window to have focus.
- Decode concurrency capped (default 1-4; heavy mode clamps to 2 when >500 frames).
- Soft preload cap of 500 frames; remaining frames decode on demand as you scrub/play.
- Soft memory ceiling (~500 MB) halts further preloads; decoding uses viewport-aware scaling plus a 1920x1080 cache cap and a 4096 px safety axis limit to avoid keeping full 6000x4000 frames in memory simultaneously.
- Cached frames cleared before reloads; decoded bitmaps frozen for lower marshaling and GC pressure.
- Corrupt image decodes are caught/logged and skipped so a single bad frame will not stop playback.
Architecture Notes
- Minimal service locator bootstrap (
App.xaml.cs) wires up services/view models without a full DI container, including a JSON-backed AppSettingsService for last/recent folders.
FrameCache handles preload/on-demand decode with viewport-aware scaling, enforces a 1920x1080 cached size cap, and keeps memory/concurrency safeguards; PlaybackMath centralizes frame index math for drop-frame/loop calculations up to 60 FPS.PlaybackController emits frame change events with elapsed time and drop counts; MainViewModel auto-starts playback post-preload, tracks dropped frames/elapsed clock, and drives UI state (preload disabling, history tray, help overlay).
Development
- Tests cover folder sorting and playback frame-index math:
dotnet test (solution).
- Project targets
net9.0-windows with WPF; no external runtime dependencies beyond the BCL.