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About
A scanned fingerprint with a printer's halftone grid baked into it. A microscopy image with scan-line banding running through it. A photo of a screen, striped with moire. The pattern degrading your image lives in the frequency domain — and most photo apps can't touch it, because they never leave pixel space. Harmonic Detective is a real-time 2D Fast Fourier Transform (FFT) workbench for images — a scientific instrument, not a photo filter. Load an image, see its frequency spectrum, draw a Region of Interest directly on that spectrum, and scale or extract exactly the frequencies you selected. WHAT YOU GET Four Synchronized Views Original, spectrum, result, and mask — always in sync, never guessing. • Original, FFT magnitude, Modified, and Mask panes update together • 2×2 grid layout on iPad and Mac, tabbed layout on iPhone • Log-scaled contrast slider auto-ranged to each image's real dynamic range Frequency-Domain ROI Tools Draw exactly where the pattern lives, in the shape that fits it. • Ellipse, rectangle, and annulus (ring) ROI shapes • Multiple ROIs at once, color-coded, combined by union masking • Move or resize by touch on iPhone/iPad, or click-and-drag on Mac • Circular ROIs render as true circles at any zoom, on any image aspect ratio Harmonic Modifier & Harmonic Isolator Scale a frequency band, or extract it in isolation. • Modifier: scale selected frequencies 0–10x to attenuate or boost a periodic pattern • Isolator: zero out everything except the selected band, to see what it alone contributes • Masks preserve full conjugate (Hermitian) symmetry — filter gain is exact, no mirror-band artifact GPU-Accelerated FFT Engine Metal-accelerated, with a CPU path validated to match it bin-for-bin. • MPSGraph (Metal) FFT handles arbitrary image dimensions — no padding required • Accelerate (vDSP) CPU engine as fallback when GPU is unavailable • 2-3 ms per FFT at 400x400, 5-8 ms at 2750x2750, GPU-accelerated Two Rotation Modes Rotate without losing your place, two different ways. • "Filter frequencies": the ROI stays fixed on screen — the filtered result changes as you rotate • "Track features": the ROI rotates with the image, staying locked to the same feature • The FFT is computed once and reused — rotating never triggers a recompute Export for Further Analysis Take your results beyond the app. • Save the modified image to Photos, or export it to Files as PNG • Export the raw FFT mask as a binary float array with metadata — for MATLAB, Python, or your own pipeline • Full, searchable user manual built into the app — no internet connection required A REAL INSTRUMENT, NOT A PHOTO FILTER Harmonic Detective doesn't apply presets or "AI enhance." You choose the frequency band, you choose scale-or-extract, and you see the math happen. Built for periodic-noise removal, pattern and texture isolation, moire and halftone analysis, and frequency-domain feature extraction — the tasks a forensic image analyst, microscopist, or signal-processing engineer already knows by name. UNIVERSAL — IPHONE, IPAD, AND MAC One purchase unlocks the full app on iPhone, iPad, and Mac (Apple silicon and Intel). No account, no sign-in, no internet connection required — every computation happens on-device. PRICING • One-time purchase: $9.99 — every feature included, no subscription, no in-app purchases, no ads Privacy Policy: https://harmonic-detective.slick-engineering.workers.dev/privacy Terms of Use: https://harmonic-detective.slick-engineering.workers.dev/terms
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