Class: Dimensions::Reader

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

Constant Summary collapse

GIF_HEADER = 
[0x47, 0x49, 0x46, 0x38]
PNG_HEADER = 
[0x89, 0x50, 0x4E, 0x47]
JPEG_HEADER = 
[0xFF, 0xD8, 0xFF]
TIFF_HEADER_I = 
[0x49, 0x49, 0x2A, 0x00]
TIFF_HEADER_M = 
[0x4D, 0x4D, 0x00, 0x2A]

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize ⇒ Reader

Returns a new instance of Reader.



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# File 'lib/dimensions/reader.rb', line 13

def initialize
  @process = :determine_type
  @type    = nil
  @width   = nil
  @height  = nil
  @angle   = nil
  @size    = 0
  @data    = ""
  @data.force_encoding("BINARY") if @data.respond_to?(:force_encoding)
end

Instance Attribute Details

#angle ⇒ Object (readonly)

Returns the value of attribute angle.



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# File 'lib/dimensions/reader.rb', line 11

def angle
  @angle
end

#height ⇒ Object (readonly)

Returns the value of attribute height.



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# File 'lib/dimensions/reader.rb', line 11

def height
  @height
end

#type ⇒ Object (readonly)

Returns the value of attribute type.



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# File 'lib/dimensions/reader.rb', line 11

def type
  @type
end

#width ⇒ Object (readonly)

Returns the value of attribute width.



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# File 'lib/dimensions/reader.rb', line 11

def width
  @width
end

Instance Method Details

#<<(data) ⇒ Object 



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# File 'lib/dimensions/reader.rb', line 24

def <<(data)
  if @process
    @data << data
    @size = @data.length
    process
  end
end

#determine_type ⇒ Object 



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# File 'lib/dimensions/reader.rb', line 36

def determine_type
  if @size >= 4
    bytes = @data.unpack("C4")

    if match_header(GIF_HEADER, bytes)
      @type = :gif
    elsif match_header(PNG_HEADER, bytes)
      @type = :png
    elsif match_header(JPEG_HEADER, bytes)
      @type = :jpeg
    elsif match_header(TIFF_HEADER_I, bytes) || match_header(TIFF_HEADER_M, bytes)
      @type = :tiff
    end

    process @type ? :"extract_#{type}_dimensions" : nil
  end
end

#extract_gif_dimensions ⇒ Object 



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# File 'lib/dimensions/reader.rb', line 54

def extract_gif_dimensions
  if @size >= 10
    @width, @height = @data.unpack("x6v2")
    process nil
  end
end

#extract_jpeg_dimensions ⇒ Object 



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# File 'lib/dimensions/reader.rb', line 68

def extract_jpeg_dimensions
  scanner = JpegScanner.new(@data)
  if scanner.scan
    @width  = scanner.width
    @height = scanner.height
    @angle  = scanner.angle

    if @angle == 90 || @angle == 270
      @width, @height = @height, @width
    end

    process nil
  end
rescue JpegScanner::ScanError
end

#extract_png_dimensions ⇒ Object 



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# File 'lib/dimensions/reader.rb', line 61

def extract_png_dimensions
  if @size >= 24
    @width, @height = @data.unpack("x16N2")
    process nil
  end
end

#extract_tiff_dimensions ⇒ Object 



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# File 'lib/dimensions/reader.rb', line 84

def extract_tiff_dimensions
  scanner = TiffScanner.new(@data)
  if scanner.scan
    @width  = scanner.width
    @height = scanner.height
    process nil
  end
rescue TiffScanner::ScanError
end

#match_header(header, bytes) ⇒ Object 



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# File 'lib/dimensions/reader.rb', line 94

def match_header(header, bytes)
  bytes[0, header.length] == header
end

#process(process = @process) ⇒ Object 



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# File 'lib/dimensions/reader.rb', line 32

def process(process = @process)
  send(@process) if @process = process
end