class PrawnPDFImage

Implements support for pulling an image out of an existing PDF and adds that image to a prawn document.

In this file, the pdf_* prefix refers to the PDF that contains the image we are adding to our document, prawn_* refers to the objects we are creating to be added to our prawn document.

Attributes

document[RW]

image_blob[RW]

reader[RW]

scaled_height[RW]

These methods are to conform to the API expected by Prawn Images and are not used internally.

scaled_width[RW]

These methods are to conform to the API expected by Prawn Images and are not used internally.

Public Class Methods

can_render?(image_blob) click to toggle source

# File lib/prawn-pdfimage.rb, line 11
def self.can_render?(image_blob)
  image_blob.unpack('C5') == [37, 80, 68, 70, 45]
end

new(image_blob) click to toggle source

# File lib/prawn-pdfimage.rb, line 15
def initialize(image_blob)
  self.image_blob = image_blob
  self.reader = ::PDF::Reader.new StringIO.new(image_blob)
end

Public Instance Methods

build_pdf_object(document) click to toggle source

# File lib/prawn-pdfimage.rb, line 20
def build_pdf_object(document)
  self.document = document

  prawn_image_reference
end

Private Instance Methods

height()

Alias for: pdf_image_height

page() click to toggle source

# File lib/prawn-pdfimage.rb, line 110
def page
  reader.page 1
end

pdf_image_bits_per_component() click to toggle source

# File lib/prawn-pdfimage.rb, line 94
def pdf_image_bits_per_component
  pdf_image_stream.hash[:BitsPerComponent]
end

pdf_image_colorspace() click to toggle source

In my tests all the PDF color spaces where contained in an ICCBased PDF reference to a dictionary with an Alternate key.

If images are not displaying correctly this is the first place to start looking.

# File lib/prawn-pdfimage.rb, line 80
def pdf_image_colorspace
  cs = pdf_image_stream.hash[:ColorSpace]

  if cs.is_a? Symbol
    cs
  else
    return cs[1].hash[:Alternate]
  end
end

pdf_image_data() click to toggle source

# File lib/prawn-pdfimage.rb, line 90
def pdf_image_data
  pdf_image_stream.unfiltered_data
end

pdf_image_filter() click to toggle source

# File lib/prawn-pdfimage.rb, line 71
def pdf_image_filter
  pdf_image_stream.hash[:Filter]
end

pdf_image_height() click to toggle source

# File lib/prawn-pdfimage.rb, line 98
def pdf_image_height
  pdf_image_stream.hash[:Height]
end

Also aliased as: height

pdf_image_stream() click to toggle source

# File lib/prawn-pdfimage.rb, line 106
def pdf_image_stream
  page.xobjects.first[1]
end

pdf_image_width() click to toggle source

# File lib/prawn-pdfimage.rb, line 102
def pdf_image_width
  pdf_image_stream.hash[:Width]
end

Also aliased as: width

pdf_soft_mask() click to toggle source

# File lib/prawn-pdfimage.rb, line 67
def pdf_soft_mask
  pdf_image_stream.hash[:SMask]
end

prawn_image_reference() click to toggle source

# File lib/prawn-pdfimage.rb, line 30
def prawn_image_reference
  document.ref!(prawn_image_reference_options).tap do |ref|
    ref << pdf_image_data
    ref.stream.filters << { pdf_image_filter => nil }
    ref.data[:SMask] = prawn_soft_mask if pdf_soft_mask
  end
end

prawn_image_reference_options() click to toggle source

# File lib/prawn-pdfimage.rb, line 38
def prawn_image_reference_options
  {
    Type:             :XObject,
    Subtype:          :Image,
    ColorSpace:       pdf_image_colorspace,
    Height:           pdf_image_height,
    Width:            pdf_image_width,
    BitsPerComponent: pdf_image_bits_per_component
  }
end

prawn_soft_mask() click to toggle source

# File lib/prawn-pdfimage.rb, line 49
def prawn_soft_mask
  document.ref!(prawn_soft_mask_options).tap do |ref|
    ref.stream << pdf_soft_mask.unfiltered_data
    ref.stream.filters << { FlateDecode: nil }
  end
end

prawn_soft_mask_options() click to toggle source

# File lib/prawn-pdfimage.rb, line 56
def prawn_soft_mask_options
  {
    Type:             :XObject,
    Subtype:          :Image,
    Width:            pdf_image_width,
    Height:           pdf_image_height,
    BitsPerComponent: pdf_image_bits_per_component,
    ColorSpace:       :DeviceGray
  }
end

width()

Alias for: pdf_image_width