Class: PNM::Image

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

Overview

Abstract base class for PBM, PGM, and PPM images.

Images can be created from pixel values, see PNM.create, or read from a file or I/O stream, see PNM.read.

See PNM module for examples.

Direct Known Subclasses

PBMImage, PGMImage, PPMImage

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Instance Attribute Details

#comment ⇒ Object (readonly)

An optional multiline comment string (or nil).



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# File 'lib/pnm/image.rb', line 33

def comment
  @comment
end

#height ⇒ Object (readonly)

The height of the image in pixels.



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# File 'lib/pnm/image.rb', line 22

def height
  @height
end

#maxgray ⇒ Object (readonly)

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



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# File 'lib/pnm/image.rb', line 26

def maxgray
  @maxgray
end

#pixels ⇒ Object (readonly)

The pixel data, given as a two-dimensional array. See PNM.create for details.



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# File 'lib/pnm/image.rb', line 30

def pixels
  @pixels
end

#width ⇒ Object (readonly)

The width of the image in pixels.



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# File 'lib/pnm/image.rb', line 19

def width
  @width
end

Class Method Details

.create(pixels, type: nil, maxgray: nil, comment: nil) ⇒ Object

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

This method should be called as PNM.create. See there for a description of pixel data formats and available options.



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# File 'lib/pnm/image.rb', line 41

def self.create(pixels, type: nil, maxgray: nil, comment: nil)
  assert_valid_array(pixels)
  assert_valid_maxgray(maxgray)
  assert_valid_comment(comment)

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

  # except for type detection, the maxgray option must be ignored for PBM
  maxgray = if type == :pbm
              nil
            else
              maxgray
            end

  image_class = case type
                when :pbm
                  PBMImage
                when :pgm
                  PGMImage
                when :ppm
                  PPMImage
                end

  image_class.new(pixels, maxgray, comment)
end

Instance Method Details

#==(other) ⇒ Object

Equality — Two images are considered equal if they have the same pixel values, type, maxgray, and comments.



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# File 'lib/pnm/image.rb', line 130

def ==(other)
  return true  if other.equal?(self)
  return false  unless other.instance_of?(self.class)

  type == other.type && maxgray == other.maxgray && comment == other.comment && pixels == other.pixels
end

#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 117

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

#inspect ⇒ Object

Returns a string representation for debugging.



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# File 'lib/pnm/image.rb', line 124

def inspect
  # implemented by subclasses
end

#type ⇒ Object

The type of the image. See PNM.create for details.



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# File 'lib/pnm/image.rb', line 14

def type
  # implemented by subclasses
end

#write(file, add_extension: false, encoding: :binary) ⇒ Object

Writes the image to file (a filename or an IO object).

When add_extension is set to true (default: false) the appropriate file extension is added to the provided filename (.pbm, .pgm, or .ppm).

The encoding can be set using the encoding keyword argument, valid options are :binary (default) and :ascii.

Returns the number of bytes written.



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# File 'lib/pnm/image.rb', line 100

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

  if file.is_a?(String)
    filename = add_extension ? "#{file}.#{type}" : file
    File.binwrite(filename, content)
  else
    file.binmode
    file.write content
  end
end