Profile Mapnik styles

style_profiler.rb

	# Mapnik style profiler
	# ruby style_profiler.rb /usr/local/share/maps/style/stylesheet.xml coloured_relief,hillshade,relief,combined_relief 8.1948 46.8982 8.4502 47.0753

	require '/usr/local/share/ruby/ffi-mapnik/lib/ffi-mapnik.rb'
	require 'nokogiri'
	require 'proj4'
	require 'benchmark'

	xml_fn = ARGV[0]
	Mapnik.register_datasources("/usr/local/lib/mapnik/input")
	Mapnik.register_fonts("/usr/local/share/maps/style/fonts")

	doc = Nokogiri::XML(File.open(xml_fn))
	print "Layers are "
	puts doc.search("Layer").collect { |l| l['name'] }.join(', ')
	if ARGV.length==1 then exit end

	# Calculate bbox
	proj = Proj4::Projection.new(["init=epsg:3857"])
	pt1  = proj.forward( Proj4::Point.new(deg2rad(ARGV[2].to_f),deg2rad(ARGV[3].to_f)) )
	pt2  = proj.forward( Proj4::Point.new(deg2rad(ARGV[4].to_f),deg2rad(ARGV[5].to_f)) )
	outbox = Mapnik::Bounds.new(pt1.x,pt1.y,pt2.x,pt2.y)
	ratio = (pt2.x-pt1.x) / (pt2.y-pt1.y)
	dx = 2000
	dy = (2000/ratio).to_i
	puts "Dimensions are #{dx}x#{dy}"

	# Run an untimed pass to pre-warm the database

	map = Mapnik::Map.new(10,10)
	print "Loading:    "; puts Benchmark.measure { map.load(xml_fn) }
	print "Resizing:   "; puts Benchmark.measure { map.resize(dx,dy) }
	print "Zooming:    "; puts Benchmark.measure { map.zoom_to(outbox) }
	print "Warming up: "; puts Benchmark.measure { map.to_file("output.png") }
	puts `ls -la output.png`

	# Now run five passes to get the standard timing

	print "Running x5: "; puts Benchmark.measure { 5.times { map.to_file("output.png") } }
	map.free
	
	# Knock out the requested layers

	puts "Knocking out layers"
	without = ARGV[1].split(',')
	doc.search("Layer").each do |layer|
		if without.include?(layer['name']) then layer['status'] = 'off' end
	end
	File.write("/tmp/knocked_out.xml", doc.to_xml)
	
	# Finally, run with the layers knocked out
	
	map = Mapnik::Map.new(10,10)
	map.load("/tmp/knocked_out.xml")
	map.resize(dx,dy)
	map.zoom_to(outbox)
	print "Running x5: "; puts Benchmark.measure { 5.times { map.to_file("output2.png") } }
	map.free

	BEGIN {
		def deg2rad(deg); deg*Proj4::DEG_TO_RAD end
	}