Harmonic Detective
Support
Frequency-domain image analysis for iPad and Mac
Getting started
- Load an image — pick a bundled test image, or load one from Photos, Files, or the camera. The FFT spectrum computes automatically and a Region of Interest (ROI) appears on it.
- Adjust the ROI — drag it on the spectrum to move it, or drag its edge to resize. The Modified and Mask views update live.
- Scale slider — controls how strongly the selected frequency band is filtered (0–10).
- Modifier vs. Isolator — Harmonic Modifier scales a band in place; Harmonic Isolator keeps only the selected band.
- Add ROI — add ellipse, rectangle, or annulus regions; they combine by union masking.
- Rotation modes — “Filter frequencies” keeps the ROI fixed on screen; “Track features” locks the ROI to the feature as you rotate.
- GPU / CPU — switch the FFT processor in Settings. GPU (Metal) is the default; the app falls back to CPU automatically where Metal is unavailable.
- Export — save the modified image to Photos or Files, or export the raw FFT mask for MATLAB / Python.
Built-in manual
Tap the ? icon in the app for a full, searchable user manual that covers every feature — no internet connection required.
Frequently asked
Do I need an account or internet connection? No. The app is fully offline and requires no sign-in.
Why does the camera / photo permission appear? Only when you explicitly capture a photo or save a result. Images are processed on-device and never uploaded. See the Privacy Policy.
The GPU option looks disabled. Metal isn't available in the iOS Simulator; on a real device or Mac the GPU path is used.
Contact
Still stuck, or have a feature request? Email ios-support@slick-engineering.com — we usually reply within a couple of business days.