Allow edge + vertex options to be passed to #write_to_graphic_file

[lskalkos]

I was using this library, and I thought it would be nice to be able to pass additional edge and vertex options into the write_to_graphic_file method -- for instance, to add a label for each edge.

The idea is that the original default options get passed in, as well as any additional ones under params['edge'] or params['vertex']. If the setting comes in the form of a Proc, then the proc is called on each edge pair or vertex. Otherwise, the setting will apply to all edges and all vertices.

Happy to add tests, or do some additional work to get this in.

Example:

graph = RGL::DirectedAdjacencyGraph["a", "b", "b", "c"]

# Edge Settings
edge_labels = {}
graph.each_edge do |b, e|
  key              = "#{b}-#{e}"
  edge_labels[key] = "#{b} to #{e}"
end
edge_label_setting = Proc.new{|b, e| edge_labels["#{b}-#{e}"]}
edge_colors = {"a-b" => "red", "b-c" => "purple"}
edge_color_setting = Proc.new{|b, e| edge_colors["#{b}-#{e}"]}
edge_settings  = {'color' => edge_color_setting, 'label' => edge_label_setting, 'fontsize' => 15}

# Vertex Settings
vertex_font_colors = {"a" => "blue", "b" => "green", "c" => "purple"}
vertex_font_color_setting = Proc.new{|b| vertex_font_colors[b]}
vertex_settings = {'fontcolor' => vertex_font_color_setting, 'fontsize' => 10}

# Options
dot_options = {'edge' => edge_settings, 'vertex' => vertex_settings}

graph.write_to_graphic_file('png', 'graph', dot_options)

[monora]

Looks good to me. Could you provide an example graph image which we could include in the README to show this feature?

I fixed the travis errors. Could you git rebase on master, then the checks should pass.

[lskalkos]

Hi there, I made a fix to the vertex settings, updated the test, and added an example to the PR description. Take a look and let me know if there is anything else that needs to be done on this. Thanks!

[monora]

Thank you, that is fine. I will mention the feature in the README.md and link to the test, which shows its usage. I will then merge the PR and make a new release.