Is it possible to separate groups of points by colour on a gmaps4rails Google maps display?

Question

I have a map display of addresses which are used for deliveries. Each address is on a particular delivery route, so it would be really handy to have the points displayed in different colours depending on the delivery route.

There are potentially a few hundred delivery addresses displayed but typically only a few delivery routes. Reading the documentation, this is possible by using different images but as I don't control the number of routes, I would rather be able to set a colour change of the existing default icon dynamically. So far I have the following in my controller:

@json = @company.addresses.where(:route_id => @premise.routes).to_gmaps4rails do |address, marker|
  marker.title "#{address.route.name}"
  # address route can be differentiated with address.route.id

end

The goal is for all addresses with a particular route id to be the same colour.

Answer 1

My answer is rather long winded but seems to work ok. I've taken some code from a blog post I found which can generate colours which are likely to be both different and readable.

I assign a different letter for each market based on the first letter of the route name. A colour is then assigned which is unique and consistent for each route. Which means even if two routes have the same first letter, there's a good chance they'll have different colours.

No doubt there is plenty of refactoring to be done!

def index
  @premise = @company.premises.find(params[:premise]) if params[:premise]

  #only generate the map info if a premise has been selected
  if @premise.present?
    @json = @company.addresses.approved.where(:route_id => @premise.routes).to_gmaps4rails do |address, marker|
      marker.picture({
        :picture => "http://chart.apis.google.com/chart?chst=d_map_pin_letter&chld=#{address.route.name[0]}|#{random_colour_by_index(address.route.name)}|000000"
      })
      marker.title "#{address.route.name}"
    end
  end
end

private

def random_colour_by_index(index)
  @colour ||= Hash.new
  @colour[index] ||= array_rgb_to_hex(hsv_to_rgb(rand, 0.5, 0.95))
end

def array_rgb_to_hex(rgb)
  rgb.inject("") { |hex, element| hex + single_rgb_to_hex(element) }
end

def single_rgb_to_hex(rgb)
  hex = rgb.to_s(16)
  rgb < 16 ? "0#{hex}" : hex
end

def hsv_to_rgb(h, s, v)
  h_i = (h*6).to_i
  f = h*6 - h_i
  p = v * (1 - s)
  q = v * (1 - f*s)
  t = v * (1 - (1 - f) * s)
  r, g, b = v, t, p if h_i==0
  r, g, b = q, v, p if h_i==1
  r, g, b = p, v, t if h_i==2
  r, g, b = p, q, v if h_i==3
  r, g, b = t, p, v if h_i==4
  r, g, b = v, p, q if h_i==5
  [(r*256).to_i, (g*256).to_i, (b*256).to_i]
end