**Input image:**

**Showing:**

**Projection:**

**Generating Elements:**

**Generating Elements:**

**Number of elements:**

**Basic quadrilateral** (heavy lines)

Rotational symmetries at intersection between:

straight lines | |

upper line and circle | |

circles | |

lower line and circle |

sum of angles =

**Size of upper circle: **

**Fractal character: **

**Center circle:** (medium line)

Rotational symmetries at intersection with

lower circle | |

upper line | |

lower line |

**Output image:**

**Output image size:**