Class: PNM::Image

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

Overview

Class for PBM, PGM, and PPM images. See PNM module for examples.

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(pixels, options = {}) ⇒ Image

Creates an image from a two-dimensional array of bilevel, gray, or RGB values.

pixels

The pixel data, given as a two-dimensional array of

  • for PBM: bilevel values (0 or 1),

  • for PGM: gray values between 0 and maxgray,

  • for PPM: an array of 3 values between 0 and maxgray, corresponding to red, green, and blue (RGB).

PPM also accepts an array of bilevel or gray values.

A value of 0 means that the color is turned off.

Optional settings that can be specified in the options hash:

type

The type of the image (:pbm, :pgm, or :ppm). By default, the type is guessed from the provided pixel data, unless this option is used.

maxgray

The maximum gray or color value. For PGM and PPM, maxgray must be less or equal 255 (the default value). For PBM pixel data, setting maxgray implies a conversion to :pgm. If type is explicitly set to :pbm, the maxgray setting is disregarded.

comment

A multiline comment string (default: empty string).



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# File 'lib/pnm/image.rb', line 52

def initialize(pixels, options = {})
  @type    = options[:type]
  @width   = pixels.first.size
  @height  = pixels.size
  @maxgray = options[:maxgray]
  @comment = (options[:comment] || '').chomp
  @pixels  = pixels

  @type ||= detect_type(@pixels, @maxgray)

  if @type == :pbm
    @maxgray = 1
  else
    @maxgray ||= 255
  end

  if type == :ppm && !pixels.first.first.kind_of?(Array)
    @pixels = pixels.map {|row| row.map {|pixel| gray_to_rgb(pixel) } }
  end
end

Instance Attribute Details

#comment ⇒ Object (readonly)

An optional multiline comment string.



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# File 'lib/pnm/image.rb', line 24

def comment
  @comment
end

#height ⇒ Object (readonly)

The height of the image in pixels.



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# File 'lib/pnm/image.rb', line 13

def height
  @height
end

#maxgray ⇒ Object (readonly)

The maximum gray or color value (for PBM always set to 1). See ::new for details.



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# File 'lib/pnm/image.rb', line 17

def maxgray
  @maxgray
end

#pixels ⇒ Object (readonly)

The pixel data, given as a two-dimensional array. See ::new for details.



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# File 'lib/pnm/image.rb', line 21

def pixels
  @pixels
end

#type ⇒ Object (readonly)

The type of the image. See ::new for details.



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# File 'lib/pnm/image.rb', line 7

def type
  @type
end

#width ⇒ Object (readonly)

The width of the image in pixels.



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# File 'lib/pnm/image.rb', line 10

def width
  @width
end

Instance Method Details

#info ⇒ Object Also known as: to_s

Returns a string with a short image format description.



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# File 'lib/pnm/image.rb', line 94

def info
  "#{type.to_s.upcase} #{width}x#{height} #{type_string}"
end

#write(file, encoding = :binary) ⇒ Object

Writes the image to file (a filename or an IO object), using the specified encoding. Valid encodings are :binary (default) and :ascii.

Returns the number of bytes written.



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# File 'lib/pnm/image.rb', line 78

def write(file, encoding = :binary)
  content = if encoding == :ascii
              to_ascii
            elsif encoding == :binary
              to_binary
            end

  if file.kind_of?(String)
    File.binwrite(file, content)
  else
    file.binmode
    file.write content
  end
end