README.md

metadata

title: Drostescher
emoji: 🐨
colorFrom: pink
colorTo: blue
sdk: gradio
sdk_version: 6.12.0
app_file: app.py
pinned: false
short_description: apply the Droste / logarithmic-spiral zoom effect

🌀 Droste Effect

Upload any image (works best with logos or images that have a transparent background) and apply the Droste / logarithmic-spiral zoom effect.

Features

Mode	Output
Still	Single warped frame (PNG)
Animation	Seamlessly looping GIF zoom

Parameters

• Width / Height – output resolution
• Frames – number of animation frames (more = smoother, slower)
• Rotations per loop – how many full turns the spiral completes in one loop
• FPS – playback speed of the exported GIF

How it works

1. Each pixel (t, l) is mapped to normalised Cartesian space (y, x) ∈ [-1,1]².
2. Polar coordinates (r, a) are computed, then logr = log₂(r).
3. The angle modulates the log-radius: logr -= na (turns circles into a spiral).
4. logr is folded into [-1, 0) so the image tiles seamlessly across octaves.
5. The inverse transform reconstructs pixel addresses, with transparent pixels resolved by stepping one octave inward until opaque colour is found.

The animation adds a time offset s ∈ [0,1) to both logr and na, producing a perfectly looping zoom-rotation.

Local usage

pip install gradio numpy numba Pillow
python app.py