Class: Writexlsx::ImageProperty

Inherits:
Object
  • Object
show all
Defined in:
lib/write_xlsx/image_property.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(filename, options = {}) ⇒ ImageProperty

Returns a new instance of ImageProperty.



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# File 'lib/write_xlsx/image_property.rb', line 12

def initialize(filename, options = {})
  @filename    = filename
  @description = options[:description]
  @decorative  = options[:decorative]
  @position    = options[:position]
  @name        = File.basename(filename)

  # Open the image file and import the data.
  data = File.binread(filename)
  @md5  = Digest::MD5.hexdigest(data)
  if data.unpack1('x A3') == 'PNG'
    process_png(data)
  elsif data.unpack1('n') == 0xFFD8
    process_jpg(data)
  elsif data.unpack1('A4') == 'GIF8'
    process_gif(data)
  elsif data.unpack1('A2') == 'BM'
    process_bmp(data)
  else
    # TODO. Add Image::Size to support other types.
    raise "Unsupported image format for file: #{filename}\n"
  end

  # Set a default dpi for images with 0 dpi.
  @x_dpi = 96 if @x_dpi == 0
  @y_dpi = 96 if @y_dpi == 0
end

Instance Attribute Details

#body ⇒ Object

Returns the value of attribute body.



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# File 'lib/write_xlsx/image_property.rb', line 10

def body
  @body
end

#decorative ⇒ Object (readonly)

Returns the value of attribute decorative.



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# File 'lib/write_xlsx/image_property.rb', line 9

def decorative
  @decorative
end

#description ⇒ Object (readonly)

Returns the value of attribute description.



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# File 'lib/write_xlsx/image_property.rb', line 9

def description
  @description
end

#filename ⇒ Object (readonly)

Returns the value of attribute filename.



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# File 'lib/write_xlsx/image_property.rb', line 9

def filename
  @filename
end

#height ⇒ Object (readonly)

Returns the value of attribute height.



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# File 'lib/write_xlsx/image_property.rb', line 8

def height
  @height
end

#md5 ⇒ Object (readonly)

Returns the value of attribute md5.



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# File 'lib/write_xlsx/image_property.rb', line 8

def md5
  @md5
end

#name ⇒ Object (readonly)

Returns the value of attribute name.



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# File 'lib/write_xlsx/image_property.rb', line 8

def name
  @name
end

#position ⇒ Object

Returns the value of attribute position.



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# File 'lib/write_xlsx/image_property.rb', line 10

def position
  @position
end

#ref_id ⇒ Object

Returns the value of attribute ref_id.



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# File 'lib/write_xlsx/image_property.rb', line 10

def ref_id
  @ref_id
end

#type ⇒ Object (readonly)

Returns the value of attribute type.



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# File 'lib/write_xlsx/image_property.rb', line 8

def type
  @type
end

#width ⇒ Object (readonly)

Returns the value of attribute width.



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# File 'lib/write_xlsx/image_property.rb', line 8

def width
  @width
end

#x_dpi ⇒ Object (readonly)

Returns the value of attribute x_dpi.



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# File 'lib/write_xlsx/image_property.rb', line 8

def x_dpi
  @x_dpi
end

#y_dpi ⇒ Object (readonly)

Returns the value of attribute y_dpi.



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# File 'lib/write_xlsx/image_property.rb', line 8

def y_dpi
  @y_dpi
end

Instance Method Details

#process_bmp(data) ⇒ Object

Extract width and height information from a BMP file.



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# File 'lib/write_xlsx/image_property.rb', line 140

def process_bmp(data)       # :nodoc:
  @type = 'bmp'

  # Check that the file is big enough to be a bitmap.
  raise "#{@filename} doesn't contain enough data." if data.bytesize <= 0x36

  # Read the bitmap width and height. Verify the sizes.
  @width, @height = data.unpack("x18 V2")
  raise "#{@filename}: largest image width #{width} supported is 65k." if width > 0xFFFF
  raise "#{@filename}: largest image height supported is 65k." if @height > 0xFFFF

  # Read the bitmap planes and bpp data. Verify them.
  planes, bitcount = data.unpack("x26 v2")
  raise "#{@filename} isn't a 24bit true color bitmap." unless bitcount == 24
  raise "#{@filename}: only 1 plane supported in bitmap image." unless planes == 1

  # Read the bitmap compression. Verify compression.
  compression = data.unpack1("x30 V")
  raise "#{@filename}: compression not supported in bitmap image." unless compression == 0

  @x_dpi = @y_dpi = 96
end

#process_gif(data) ⇒ Object

Extract width and height information from a GIF file.



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# File 'lib/write_xlsx/image_property.rb', line 128

def process_gif(data)
  @type  = 'gif'
  @x_dpi = 96
  @y_dpi = 96

  @width  = data[6, 2].unpack1("v")
  @height = data[8, 2].unpack1("v")

  raise "#{@filename}: no size data found in gif image.\n" if @height.nil?
end

#process_jpg(data) ⇒ Object 



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# File 'lib/write_xlsx/image_property.rb', line 82

def process_jpg(data)
  @type  = 'jpeg'
  @x_dpi = 96
  @y_dpi = 96

  offset = 2
  data_length = data.bytesize

  # Search through the image data to read the JPEG markers.
  while offset < data_length
    marker  = data[offset + 0, 2].unpack1("n")
    length  = data[offset + 2, 2].unpack1("n")

    # Read the height and width in the 0xFFCn elements
    # (Except C4, C8 and CC which aren't SOF markers).
    if (marker & 0xFFF0) == 0xFFC0 &&
       marker != 0xFFC4 && marker != 0xFFCC
      @height = data[offset + 5, 2].unpack1("n")
      @width  = data[offset + 7, 2].unpack1("n")
    end

    # Read the DPI in the 0xFFE0 element.
    if marker == 0xFFE0
      units     = data[offset + 11, 1].unpack1("C")
      x_density = data[offset + 12, 2].unpack1("n")
      y_density = data[offset + 14, 2].unpack1("n")

      if units == 1
        @x_dpi = x_density
        @y_dpi = y_density
      elsif units == 2
        @x_dpi = x_density * 2.54
        @y_dpi = y_density * 2.54
      end
    end

    offset += length + 2
    break if marker == 0xFFDA
  end

  raise "#{@filename}: no size data found in jpeg image.\n" unless @height
end

#process_png(data) ⇒ Object

Extract width and height information from a PNG file.



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# File 'lib/write_xlsx/image_property.rb', line 43

def process_png(data)
  @type   = 'png'
  @width  = 0
  @height = 0
  @x_dpi  = 96
  @y_dpi  = 96

  offset = 8
  data_length = data.size

  # Search through the image data to read the height and width in th the
  # IHDR element. Also read the DPI in the pHYs element.
  while offset < data_length

    length = data[offset + 0, 4].unpack1("N")
    png_type   = data[offset + 4, 4].unpack1("A4")

    case png_type
    when "IHDR"
      @width  = data[offset + 8, 4].unpack1("N")
      @height = data[offset + 12, 4].unpack1("N")
    when "pHYs"
      x_ppu = data[offset + 8,  4].unpack1("N")
      y_ppu = data[offset + 12, 4].unpack1("N")
      units = data[offset + 16, 1].unpack1("C")

      if units == 1
        @x_dpi = x_ppu * 0.0254
        @y_dpi = y_ppu * 0.0254
      end
    end

    offset = offset + length + 12

    break if png_type == "IEND"
  end
  raise "#{@filename}: no size data found in png image.\n" unless @height
end