This is a small snippet to change the size of an input image to iconsize of Firefoxphone

Icon_creator.rb

require 'opencv'
include OpenCV

if ARGV.size == 0
  puts "Usage: ruby #{__FILE__} ImageToLoadAndDisplay"
  exit
end

image = nil
begin
  image = CvMat.load(ARGV[0], CV_LOAD_IMAGE_UNCHANGED	) # Read the file.
rescue
  puts 'Could not open or find the image.'
  exit
end
sizes = [512,128,58,48,16]
sizes.each do |s|
	size = CvSize.new(s,s)
	tmp_image = image.resize(size)
	tmp_image.save("Icon_#{s}.png")
end