compass-config-with-png-compression.rb

project_path = File.dirname(__FILE__) + "/"
utils_dir = "utilities/"
utils_path =  project_path + utils_dir

# callback - on_sprite_saved
# http://compass-style.org/help/tutorials/configuration-reference/
on_sprite_saved do |filename|  
	if File.exists?(filename)
		# Post process sprite image
		postprocesspng(filename, utils_path)
	end
end

# fn - Post processing for pngs
# http://compass-style.org/help/tutorials/configuration-reference/
# http://pngquant.org/
# http://advsys.net/ken/utils.htm & http://nicj.net/2012/05/15/pngoutbatch
# http://optipng.sourceforge.net/
def postprocesspng(filename, utils_path)
	if File.exists?(filename)
		sleep 1
		optimize(filename, utils_path + "pngquant/pngquant --verbose --force --ext .png 256")
		optimize(filename, utils_path + "pngout/pngoutbatch.cmd")
		optimize(filename, utils_path + "optipng/optipng -o7 -verbose")
	end
end

# fn - Run optimize command line for a specified script
# https://gist.github.com/2403117
def optimize(filename, script)
	if File.exists?(filename)
		sleep 1
		system script + " " + filename
	end
end