<?xml version="1.0" encoding="ISO-8859-1"?>

<screensaver name="tessellimage" _label="Tessellimage">

  <command arg="--root"/>

  <video href="https://www.youtube.com/watch?v=JNgybysnYU8"/>

  <hgroup>
   <vgroup>
    <number id="delay" type="slider" arg="--delay %"
            _label="Frame rate" _low-label="Low" _high-label="High"
            low="0" high="100000" default="30000"
            convert="invert"/>

    <number id="duration2" type="slider" arg="--duration2 %"
            _label="Speed" _low-label="0.1 second" _high-label="4 seconds"
            low="0.1" high="4.0" default="0.4"/>

    <number id="duration" type="slider" arg="--duration %"
            _label="Duration" _low-label="10 seconds" _high-label="10 minutes"
            low="10" high="600" default="120"/>

    <number id="depth" type="slider" arg="--max-depth %"
            _label="Complexity" _low-label="Shallow" _high-label="Deep"
            low="1000" high="100000" default="30000"/>
   </vgroup>

   <vgroup>

    <select id="mode">
     <option id="random" _label="Delaunay or voronoi"/>
     <option _label="Delaunay" arg-set="--mode delaunay"/>
     <option _label="Voronoi"  arg-set="--mode voronoi"/>
    </select>

    <xscreensaver-image />

    <boolean id="fill"    _label="Fill screen" arg-unset="--no-fill-screen"/>
    <boolean id="outline" _label="Outline triangles" arg-unset="--no-outline"/>
    <boolean id="showfps" _label="Show frame rate" arg-set="--fps"/>

    <xscreensaver-updater />
   </vgroup>
  </hgroup>

  <_description>
Converts an image to triangles using Delaunay tessellation, or to
polygons using Voronoi tesselation, and animates the result at
various depths.

More polygons are allocated to visually complex parts of the image.
This is accomplished by first computing the first derivative of the
image: the distance between each pixel and its neighbors (which is
essentially edge detection or embossing).  Then the Delaunay or
Voronoi control points are chosen by selecting those pixels whose
distance value is above a certain threshold: those are the pixels that
have the largest change in color/brightness.

https://en.wikipedia.org/wiki/Delaunay_triangulation
https://en.wikipedia.org/wiki/Voronoi_diagram
https://en.wikipedia.org/wiki/Tessellation

Written by Jamie Zawinski; 2014.
  </_description>
</screensaver>
