slicer.rb

#! /usr/bin/ruby -w
require 'rubygems'
require 'rmagick'
require 'fileutils'
include Magick

puts 'Go!'

limit = ARGV.length > 1 ? ARGV[1].to_i : 18
file = ARGV[0]
 
	puts "Processing #{file} with depth of #{limit}"
 
	# Check file exists
	unless File::exists?( file )
		puts "Image #{file} not found"
		abort("Image #{file} not found")
	end
 
	#Setup
	img_name = File.basename(file, ".jpg")
	
	# Load the source image and a little information
	img = Magick::Image.read(file).first
	w = img.columns
	h = img.rows
 
	puts "Image #{file} too small (<512x512)" and abort('') unless (h > 512 || w > 512)
 
	FileUtils.rm_rf(img_name) if File::directory?(img_name)
	dir_name = img_name.split('.').slice(0,img_name.split('.').length - 1).to_s.gsub('["', '').gsub('"]', '');
	puts dir_name;
	Dir.mkdir(dir_name)
 
	  # Find the next largest multiple of 256 and the power of 2
  dim = w > h ? w : h
  pow = -1
  
  loop do
    i = 256*(2**pow+=1)
    next if i < dim
    dim = i
    break
  end
 
  # Resize the source image up to the larger size
  if (dim > w && dim > h)
  	puts "Resizing image to #{dim}px"
    # Determine the optimal pixel radius for sharpening
 
    img.change_geometry!("#{dim}x#{dim}") { |cols, rows, i|
 		 i.resize!(cols, rows)
 	  }
        sharp = ( w/dim > h/dim ? dim/w : dim/h )/2
    img = img.sharpen(sharp)
  end
 
  # Build a new square image with a black background, and composite the source image on top of it.
  master = Magick::Image.new(dim,dim){ self.background_color = "transparent" }
  master.composite!(img, Magick::CenterGravity, Magick::OverCompositeOp)
 
 
 
  img = nil
 
  # Create slice layers
  layer = 0
  loop do
    # Google Maps only allows 19 layers (though I doubt we'll ever reach this point).
    break if layer > limit
    width = 256*(2**layer)
 
    break if width > dim
    Dir.mkdir("#{dir_name}/#{layer}", 0775) unless File::directory?("#{dir_name}/#{layer}")
 
    crop_master = master.clone
    crop_master.resize!(width, width)
 
    max_loop = (width / 256) - 1
 
    (0 .. max_loop).each do |x|
      Dir.mkdir("#{dir_name}/#{layer}/#{x}", 0775) unless File::directory?("#{dir_name}/#{layer}/#{x}")
      (0 .. max_loop).each do |y|
		crop = crop_master.clone
		crop.crop!( x*256, crop_master.rows - ((y + 1) * 256), 256, 256) 
		crop.write("#{dir_name}/#{layer}/#{x}/#{y}.jpg")
		crop = nil
      end
    end
    
    layer+=1
    crop_master = nil
  end
 
  master = nil