class PixelChart

PixelChart class

Public Class Methods

dimensions(area) click to toggle source

Calculate the possible dimensions (width, height) for a given area @param area [Integer] number of values, total of pixels @return [Array<Array<Integer>>] Array of possible dimensions

# File lib/pixelchart.rb, line 60
def self.dimensions(area)
  dim = []
  (1..Math.sqrt(area).to_i).each do |x|
    y, rem = area.divmod(x)
    dim.push([x, y]) if rem.zero?
  end
  dim
end

load_file(filename) click to toggle source

Read the input file to extract the values @param filename [String] Name of the input file containing data. Values must

be 0, 1, true, false and separated by commas.

@return [Array<Integer>] Array of 0, 1. Can be directly passed to initialize

# File lib/pixelchart.rb, line 79
def self.load_file(filename)
  content = File.read(filename).gsub(/\s+/, '')
  data = content.split(',')
  data.each_with_index do |x, i|
    data[i] = 0 if x == '0' || x.downcase == 'false'
    data[i] = 1 if x == '1' || x.downcase == 'true'
  end
  data
end

new(data, width, height, opts = {}) click to toggle source

A new instance of PixelChart @param data [Array<Boolean>] An array containing values

(0, 1) used to generate the image.

@param width [Integer] Desired width of the image. @param height [Integer] Desired height of the image. @option opts [Array<Color>] :colors Must be an array containing 2 values.

Each value is either the `:random` symbol to get a random color or a
color given as RGB, so 3 integers in an array.

@option opts [Scale] :scale Scale the image to dimensions or with a ratio.

Ratio must be a positive (non-nul) float or integer, and dimensions must
be a set of width and height separated by a comma.

# File lib/pixelchart.rb, line 27
def initialize(data, width, height, opts = {})
  @width = check_int(width)
  @height = check_int(height)
  @data = check_data(data)
  opts[:colors] ||= [[255, 255, 255], [0, 0, 0]] # white, black
  check_colors(opts[:colors])
  opts[:colors].each_with_index do |color, i|
    opts[:colors][i] = (0..2).map { |_x| rand(256) } if color == :random
  end
  @colors = opts[:colors]
  opts[:scale] ||= nil
  @scale = opts[:scale]
end

Public Instance Methods

dimensions() click to toggle source

Calculate the possible dimensions (width, height) for the data of the object @return [Array<Array<Integer>>] Array of possible dimensions

# File lib/pixelchart.rb, line 71
def dimensions
  dimensions(@data.size)
end

draw(filename, opts = {}) click to toggle source

Generate and save the image @param filename [String] Name of the output image. @param opts [Hash] options for image processing @option opts [Symbol] :backend Image processing backend, ‘:rmagick` for

Rmagick/Imagemagick or `:rubyvips` for ruby-vips/libvips.

# File lib/pixelchart.rb, line 46
def draw(filename, opts = {})
  opts[:backend] ||= :rmagick
  backend = check_backend(opts[:backend])
  case backend
  when :rmagick
    draw_rmagick(filename)
  when :rubyvips
    draw_rubyvips(filename)
  end
end

Private Instance Methods

check_backend(data) click to toggle source

Check if the backend option is in the format expected by draw else raise

an error

@param data [Object] The object to check @return [Object] Untouched input object

# File lib/pixelchart.rb, line 192
def check_backend(data)
  accepted_values = %i[rmagick rubyvips]
  raise(ArgumentError, "Backend must be #{accepted_values.join(' or ')}") unless accepted_values.include?(data)

  data
end

check_colors(data) click to toggle source

Check if the colors are in the format expected by initialize else raise an

error

@param data [Object] The object to check @return [Object] Untouched input object

# File lib/pixelchart.rb, line 167
def check_colors(data)
  raise(ArgumentError, 'Argument is not an array') unless data.is_a?(Array)

  data.each do |item|
    case item
    when :random
      # nothing
    when Array
      raise(ArgumentError, 'RGB must contains 3 values') unless item.size == 3

      item.each do |i|
        raise(ArgumentError, 'RGB values are not integers') unless i.is_a?(Integer)
        raise(ArgumentError, 'RGB values must be between 0 and 255') unless (0..255).include?(i)
      end
    else
      raise(ArgumentError, 'Colors are not a RGB array or :random')
    end
  end
  data
end

check_data(data) click to toggle source

Check if the data is in the format expected by initialize else raise an

error

@param data [Object] The object to check @return [Object] Untouched input object

# File lib/pixelchart.rb, line 150
def check_data(data)
  raise(ArgumentError, 'Argument is not an array') unless data.is_a?(Array)

  possible_values = PixelChart.dimensions(data.size)
  possible_sets = possible_values.map(&:to_set)

  unless possible_sets.include?(Set[@width, @height])
    raise(ArgumentError, 'The number of values does not match with the possible dimensions')
  end

  data
end

check_int(data) click to toggle source

Check if the argument is an integer else raise an error @param data [Object] The object to check @return [Object] Untouched input object

# File lib/pixelchart.rb, line 140
def check_int(data)
  raise(ArgumentError, 'Argument is not an integer') unless data.is_a?(Integer)

  data
end

draw_rmagick(filename) click to toggle source

Generate and save the image with Rmagick @param filename [String] Name of the output image.

# File lib/pixelchart.rb, line 93
def draw_rmagick(filename)
  img = Magick::Image.new(@width, @height)
  i = 0
  (0...@height).each do |y|
    (0...@width).each do |x|
      if [1, true].include?(@data[i]) # true color
        img.pixel_color(x, y, "rgb(#{@colors[1].join(',')}")
      else # false color
        img.pixel_color(x, y, "rgb(#{@colors[0].join(',')})")
      end
      i += 1
    end
  end
  unless @scale.nil?
    case @scale
    when Numeric
      raise(ArgumentError, 'Scale must be a ratio or a set of width and height') if @scale.zero?

      img.scale!(@scale)
    when Array
      img.scale!(@scale[0], @scale[1])
    else
      raise(ArgumentError, 'Scale must be a ratio or a set of width and height')
    end
  end
  img.write(filename)
end

draw_rubyvips(filename) click to toggle source

Generate and save the image ruby-vips @param filename [String] Name of the output image.

# File lib/pixelchart.rb, line 123
def draw_rubyvips(filename)
  # true -> 1, false -> 0
  @data.map! { |x| x == true ? 1 : x }
  @data.map! { |x| x == false ? 0 : x }
  # make a 2D image from the data array
  im = Vips::Image.new_from_array(@data.each_slice(@width).to_a)
  im = (im == 1).ifthenelse(@colors[1], @colors[0], blend: true)
  if @scale.is_a?(Numeric)
    opts = { kernel: :nearest }
    im = im.resize(@scale, **opts)
  end
  im.write_to_file(filename, compression: 9, palette: true, colours: 2, Q: 0)
end