evolution

Evolution is a Ruby implementation of a hill-climbing algorithm that uses RMagick to generate a collection of polygons which resemble a baseline image. It does this by starting with a blank canvas and a single polygon with random points, color and opacity. It then takes the original polygon and randomly mutates it (by moving a point, adding a point or changing the color / opacity), or adds a new random polygon. Between the original image and the mutated version, whichever one more closely resembles the baseline is kept and used to seed the next mutation.

     generation: 1               generation: 2              generation: 3

 +-------------------+       +-------------------+      +-------------------+
 | image 001         |       | image 002         |      | image 002         |
 | similarity: 3.0 % |   +-->| similarity: 3.2 % |----->| similarity: 3.2 % |    +--> ...
 +-------------------+   |   +-------------------+      +-------------------+    |
           |             |             |                          |              |
           |             |             |                          |              |
    random mutation      |      random mutation            random mutation       |
           |             |             |                          |              |
           v             |             v                          v              |
 +-------------------+   |   +-------------------+      +-------------------+    |
 | image 002         |---+   | image 003         |      | image 004         | ---+
 | similarity: 3.2%  |       | similarity: 3.1%  |      | similarity: 3.3%  |
 +-------------------+       +-------------------+      +-------------------+

Usage

git clone https://github.com/joeyschoblaska/evolution.git
cd evolution
bundle
rake run

Rendered images and svg files will be placed in the images/renders directory.

Options

The following environment variables can be set when using the rake run command:

baseline_image: The path to the image you want to render. The larger the image, the more time it will take RMagick to compare each set of candidates, and the longer it will take to converge. Default: './images/baseline.jpg'

canvas_background: The color of the canvas, behind the rendered polygons. Default: 'white'

add_polygon_mutation_rate: The rate at which new polygons will occur during mutations. There is a 1/x chance of this mutation occuring, so setting it to 1 will result in a new polygon in each mutation, while setting it to 100 will result in a 1% chance of a new polygon being added in each mutation. Default: 100

rgba_mutation_rate: The rate at which polygons will have their RGBA values changed during mutations. There is a 1/x chance of this mutation occuring. Default: 300

point_mutation_rate: The rate at which points will have their coordinates changed during mutations. There is a 1/x chance of this mutation occuring. Default: 200

add_point_mutation_rate: The rate at which new points will be added to polygons during mutations. There is a 1/x chance of this mutation occuring. Default: 1000

fitness_target: Each candidate receives a "fitness" score according to how similar it is to the target baseline image, with a score of 0 indicating a perfect match. The fitness_target is the value which, when reached, will cause the program to end. Default: 500

write_frequency: Every x successful mutations, render the image to the images/renders directory and save the svg string. Default: 50