Class: Tiler

Inherits:
Object
  • Object
show all
Defined in:
lib/imagetiler.rb

Constant Summary collapse

TILE_SIZE = 
256

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize ⇒ Tiler

Returns a new instance of Tiler.



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# File 'lib/imagetiler.rb', line 31

def initialize()
	@zoom_levels = 0..4
	@bg_color = Magick::Pixel.new(255,255,255,Magick::TransparentOpacity)
	@format = "png"
	@autocreate_dirs = true
	@output_dir = "."
	@prefix = "tile"
end

Instance Attribute Details

#autocreate_dirs ⇒ Object

Returns the value of attribute autocreate_dirs.



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# File 'lib/imagetiler.rb', line 28

def autocreate_dirs
  @autocreate_dirs
end

#bg_color ⇒ Object

Returns the value of attribute bg_color.



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# File 'lib/imagetiler.rb', line 28

def bg_color
  @bg_color
end

#format ⇒ Object

Returns the value of attribute format.



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# File 'lib/imagetiler.rb', line 28

def format
  @format
end

#output_dir ⇒ Object

Returns the value of attribute output_dir.



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# File 'lib/imagetiler.rb', line 28

def output_dir
  @output_dir
end

#prefix ⇒ Object

Returns the value of attribute prefix.



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# File 'lib/imagetiler.rb', line 28

def prefix
  @prefix
end

#zoom_levels ⇒ Object

Returns the value of attribute zoom_levels.



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# File 'lib/imagetiler.rb', line 28

def zoom_levels
  @zoom_levels
end

Instance Method Details

#calc_native_res_zoom(image_source) ⇒ Object

Calculates the zoom level closest to native resolution. Returns a float for the zoom – so, use zoom.ceil if you want the higher zoom, for example



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# File 'lib/imagetiler.rb', line 85

def calc_native_res_zoom(image_source)
	image = get_image(image_source)
	side_length = calc_side_length(image)
	zoom = log2(side_length)-log2(TILE_SIZE)
	zoom = 0 if zoom < 0
	zoom
end

#calc_side_length(image) ⇒ Object 



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# File 'lib/imagetiler.rb', line 113

def calc_side_length(image)
	long_side = [image.columns, image.rows].max
	max_zoom = @zoom_levels.max
	ceil = (long_side.to_f()/2**max_zoom).ceil
	side_length = ceil*2**max_zoom
end

#create_dir(dir) ⇒ Object

if dir does not exist, create it



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# File 'lib/imagetiler.rb', line 121

def create_dir(dir)
	if !FileTest::directory?(dir)
		Dir::mkdir(dir)
	end
end

#get_image(image_source) ⇒ Object 



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# File 'lib/imagetiler.rb', line 103

def get_image(image_source)
	case image_source
	when Magick::Image
		image = image_source
	else
		image = Magick::ImageList::new(image_source)
	end
	return image
end

#log2(x) ⇒ Object 



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# File 'lib/imagetiler.rb', line 127

def log2(x)
	Math.log(x)/Math.log(2)
end

#make_tiles(image_source, opts = {}) ⇒ Object

image_source can either be an RMagick Image or a string specifying the filename



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# File 'lib/imagetiler.rb', line 41

def make_tiles(image_source, opts={})

	# initializing and setting options and stuff
	image = get_image(image_source)
	opts.each_pair do |key,value|
      instance_variable_set "@#{key}", value
   end

	if @autocreate_dirs
		create_dir(output_dir)
	end

	# pad image with background color so image is square
	image_sq = pad_image(image)
	image_length = image_sq.columns

	# the actual tiling part!
	zoom_levels.each do |zoom|
		# get the number of tiles in each column and row
		factor = 2 ** zoom

		# get length of tiles for current zoom
		tile_length = image_length / factor

		0.upto(factor-1) do |col|
			0.upto(factor-1) do |row|

				# cut tile
				# Image.crop(x,y,width,height,toss offset information)
				tile = image_sq.crop(col*tile_length, row*tile_length,
														 tile_length, tile_length, true)
				tile.resize!(TILE_SIZE,TILE_SIZE)

				# output tile
				filename = File.join(@output_dir, "#{prefix}_#{zoom}_#{col}_#{row}.#{@format}")
				tile.write(filename)
			end
		end
	end
end

#pad_image(image) ⇒ Object

pad image to the lower right with bg_color so that the image is square and that the max number of pixels is evenly divisible by the max number of tiles per side



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# File 'lib/imagetiler.rb', line 96

def pad_image(image)
	dim = calc_side_length(image)
	
	image.background_color = @bg_color
	image.extent(dim, dim)
end