map.rb

require 'rubygems'
require 'simpler_tiles'

breaks  = [0.05, 0.15, 0.30, 0.45, 0.60]
cbreaks = [0.40, 0.50, 0.60, 0.70, 0.80]
colors  = [[236, 231, 242], [166, 189, 219], [116, 169, 207], [54, 144, 192], [5, 112, 176], [3, 78, 123]]

def color(color)
  sprintf("#%2x%2x%2x", *color).gsub(" ", "0")
end

map = SimplerTiles::Map.new do |m|
  m.srs = "EPSG:102003"
  m.set_bounds -2356113.743199, -1337508.077280, 2258243.997100, 1565781.660000
  m.width  = 630
  m.height = 400
  m.layer '10m-ocean/10m_ocean.shp' do |l|
    l.query 'select * from "10m_ocean"' do |q|
      q.styles 'fill' => '#eaeaea',
           'seamless' => 'true',
          "line-join" => 'round'
    end
  end
  m.layer 'us.shp' do |l|
    l.query 'select * from "us"' do |q|
      q.styles 'stroke' => '#888888',
            'line-join' => 'round',
               'weight' => '0.2'
    end
  end
  m.layer '10m-lakes/ne_10m_lakes.shp' do |l|
    l.query 'select * from "ne_10m_lakes"' do |q|
      q.styles 'fill' => '#eaeaea',
           'seamless' => 'true',
          "line-join" => 'round'
    end
  end
end

File.open("images/background.png", 'w+') {|f| f.write map.to_png }

(1890..2010).step(10).each do |epoch|
  p epoch
  map = SimplerTiles::Map.new do |m|
    m.srs = "EPSG:102003"
    m.set_bounds -2356113.743199, -1337508.077280, 2258243.997100, 1565781.660000
    m.width  = 630
    m.height = 400

    m.layer 'PG:dbname=migration' do |l|
      breaks.each_with_index do |brk, i|
        l.query "SELECT * FROM counties where black::float / total > #{brk} and total > 100 and epoch = #{epoch}" do |q|
          q.styles "seamless" => 'true',
                       "fill" => color(colors[i]),
                  "line-join" => 'round'
        end
      end
    end
  end

  File.open("images/#{epoch}.png", 'w+') {|f| f.write map.to_png }
  p epoch
end