module Colorpress

Constants

VERSION

Public Class Methods

decode(image_name, output_name=nil, cleanup=true) click to toggle source

Decode a file from PNG format.

@param image_name [String] the name of the image to decode, ex: 'filename.txt.png' @param output_name [String, nil] the name of the output file (no extension needed), ex: 'my_file' @param cleanup [Boolean] whether to delete PNG file after decoding

# File lib/colorpress.rb, line 38
def self.decode(image_name, output_name=nil, cleanup=true)
  output_name = image_name[0...-4] unless output_name # Remove .png extension
  image = ChunkyPNG::Image.from_file(image_name)

  write_data(output_name, '', true) # Make sure the output file is empty

  bytes = []
  (0..image.dimension.height-1).each do |y|
    (0..image.dimension.width-1).each do |x|
      # It's either red, green, or blue, so add them all
      bytes << ChunkyPNG::Color.r(image[x, y]) +
        ChunkyPNG::Color.g(image[x, y]) +
        ChunkyPNG::Color.b(image[x, y])
    end
    write_data(output_name, bytes)
    bytes = []
  end

  write_data(output_name, bytes) if bytes.any? # Write if any bytes still in array

  File.delete(image_name) if cleanup
end

encode(file_name, output_name=nil, min_width=50) click to toggle source

Encode a file to PNG format.

@param file_name [String] the name of the file to encode @param output_name [String, nil] the optional name of the output file @param min_width [Integer] the minimum width of the image, in pixels

# File lib/colorpress.rb, line 10
def self.encode(file_name, output_name=nil, min_width=50)
  file_size = File.stat(file_name).size
  # Increase width until it divides number of bytes evenly
  while file_size % min_width != 0
    min_width += 1
  end
  image = ChunkyPNG::Image.new(min_width, file_size/min_width)

  y = 0
  read_bytes(file_name, min_width) do |buffer|
    unpacked_data = buffer.unpack('C*')
    unpacked_data.each_with_index do |value, index|
      # Randomly pick between red/green/blue
      rgb = [0, 0, 0]
      rgb[(rand * 3).to_i] = value
      image[index, y] = ChunkyPNG::Color.rgb(*rgb)
    end
    y += 1
  end

  image.save(output_name.nil? ? file_name + '.png' : output_name)
end

Private Class Methods

read_bytes(filename, buffer_size=20) { |buffer| ... } click to toggle source

Reads bytes from a file into a buffer, yielding the buffer to a given block.

@param filename [String] the name of the file to read @param buffer_size[Integer, nil]

amount of bytes to read into the buffer at a time

@example Reading all of a file

other_bytes = ''
Colorpress::FileIO.read_bytes('filename.txt', 20) do |buffer|
  other_bytes += buffer
end
# other_bytes now contains all bytes of the file

# File lib/colorpress.rb, line 75
def self.read_bytes(filename, buffer_size=20)
  File.open(filename, 'rb') do |file|
    until file.eof? do
      buffer = file.read(buffer_size)
      yield buffer
    end
  end
end

write_data(filename, data, truncate=false) click to toggle source

Writes the given data to the given filename. Truncates the file if desired.

@param filename [String] the name of the file to write @param data [String, Array] the data to write to the file,

it may be a string or an array of bytes

@param truncate [Boolean] whether or not to empty the file before writing

# File lib/colorpress.rb, line 90
def self.write_data(filename, data, truncate=false)
  mode = truncate ? 'wb' : 'ab'
  File.open(filename, mode) do |file|
    data = data.pack('C*') if data.is_a? Array
    file.write(data)
  end
end