Class: Pdfrb::Document::FormXObject

Inherits:
Object
  • Object
show all
Defined in:
lib/pdfrb/document/form_xobject.rb

Overview

Form XObject facade. Creates reusable form templates that can be drawn on multiple pages via the /Do operator. A Form XObject is a stream with /Type (omitted), /Subtype /Form, /BBox, and optional /Matrix + /Resources.

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(document, name: nil, bbox: nil, matrix: nil) ⇒ FormXObject

Returns a new instance of FormXObject.



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# File 'lib/pdfrb/document/form_xobject.rb', line 12

def initialize(document, name: nil, bbox: nil, matrix: nil)
  @document = document
  @bbox = bbox || [0, 0, 612, 792]
  @matrix = matrix

  dict = { Subtype: :Form, BBox: @bbox }
  dict[:Matrix] = @matrix if @matrix
  @stream = document.add(dict, type: Pdfrb::Model::Cos::Stream)
  @name = (name || "Form#{@stream.oid}").to_sym
  @canvas = nil
end

Instance Attribute Details

#document ⇒ Object (readonly)

Returns the value of attribute document.



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# File 'lib/pdfrb/document/form_xobject.rb', line 10

def document
  @document
end

#name ⇒ Object (readonly)

Returns the value of attribute name.



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# File 'lib/pdfrb/document/form_xobject.rb', line 10

def name
  @name
end

#stream ⇒ Object (readonly)

Returns the value of attribute stream.



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# File 'lib/pdfrb/document/form_xobject.rb', line 10

def stream
  @stream
end

Instance Method Details

#canvas ⇒ Object

Returns a Canvas for drawing into this Form XObject. The Canvas writes to the Form XObject's content stream.



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# File 'lib/pdfrb/document/form_xobject.rb', line 26

def canvas
  return @canvas if @canvas

  contents_stream = @document.add({}, type: Pdfrb::Model::Cos::Stream)
  @stream.value[:Resources] = {}
  @canvas = Pdfrb::Content::Canvas.new(contents_stream, document: @document)
  @stream.stream = +"".b # placeholder; filled by ensure_stream_payload
  @contents_stream = contents_stream
  @canvas
end

#draw_on(target_canvas, at:, scale: 1.0) ⇒ Object

Draw this Form XObject on a canvas at the given position.



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# File 'lib/pdfrb/document/form_xobject.rb', line 59

def draw_on(target_canvas, at:, scale: 1.0)
  target_canvas.emit_op(Pdfrb::Content::Operator::SaveGraphicsState)
  target_canvas.translate(at[0], at[1])
  target_canvas.scale(scale) if (scale - 1.0).abs > 1e-9
  target_canvas.append(" /#{@name} Do\n")
  target_canvas.emit_op(Pdfrb::Content::Operator::RestoreGraphicsState)
end

#finalize! ⇒ Object

Finalize: copy the canvas content into the Form XObject stream and register it in the document's resource names. Called automatically before write.



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# File 'lib/pdfrb/document/form_xobject.rb', line 40

def finalize!
  return unless @contents_stream

  @stream.stream = @contents_stream.stream
  @stream.value[:Resources] = @contents_stream.value[:Resources] || {}
end

#register_on_page(page) ⇒ Object

Register this Form XObject in a page's /Resources /XObject dict so it can be referenced via the /Do operator.



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# File 'lib/pdfrb/document/form_xobject.rb', line 49

def register_on_page(page)
  resources = page.value[:Resources]
  resources = {} unless resources.is_a?(::Hash)
  xobjects = resources[:XObject] || {}
  xobjects[@name] = Pdfrb::Model::Reference.new(@stream.oid, @stream.gen)
  resources[:XObject] = xobjects
  page.value[:Resources] = resources
end