Prawn::Graphics::Transparency

The Prawn::Transparency module is used to place transparent content on the page. It has the capacity for separate transparency values for stroked content and all other content.

Example:

  # both the fill and stroke will be at 50% opacity
  pdf.transparent(0.5) do
    pdf.text("hello world")
    pdf.fill_and_stroke_circle([x, y], 25)
  end

  # the fill will be at 50% opacity, but the stroke will
  # be at 75% opacity
  pdf.transparent(0.5, 0.75) do
    pdf.text("hello world")
    pdf.fill_and_stroke_circle([x, y], 25)
  end

Public Instance Methods

transparent(opacity, stroke_opacity=opacity, &block) click to toggle source

Sets the opacity and stroke_opacity for all the content within the block If stroke_opacity is not provided, then it takes on the same value as opacity

Valid ranges for both paramters are 0.0 to 1.0

Example:

  # both the fill and stroke will be at 50% opacity
  pdf.transparent(0.5) do
    pdf.text("hello world")
    pdf.fill_and_stroke_circle([x, y], 25)
  end

  # the fill will be at 50% opacity, but the stroke will
  # be at 75% opacity
  pdf.transparent(0.5, 0.75) do
    pdf.text("hello world")
    pdf.fill_and_stroke_circle([x, y], 25)
  end

    # File lib/prawn/graphics/transparency.rb, line 54
54:       def transparent(opacity, stroke_opacity=opacity, &block)
55:         min_version(1.4)
56: 
57:         opacity        = [[opacity, 0.0].max, 1.0].min
58:         stroke_opacity = [[stroke_opacity, 0.0].max, 1.0].min
59: 
60:         save_graphics_state
61:         add_content "/#{opacity_dictionary_name(opacity, stroke_opacity)} gs"
62:         yield
63:         restore_graphics_state
64:       end

Private Instance Methods

next_opacity_dictionary_id() click to toggle source

    # File lib/prawn/graphics/transparency.rb, line 72
72:       def next_opacity_dictionary_id
73:         opacity_dictionary_registry.length + 1
74:       end

opacity_dictionary_name(opacity, stroke_opacity) click to toggle source

    # File lib/prawn/graphics/transparency.rb, line 76
76:       def opacity_dictionary_name(opacity, stroke_opacity)
77:         key = "#{opacity}_#{stroke_opacity}"
78: 
79:         if opacity_dictionary_registry[key]
80:           dictionary =  opacity_dictionary_registry[key][:obj]
81:           dictionary_name =  opacity_dictionary_registry[key][:name]
82:         else
83:           dictionary = ref!(:Type => :ExtGState,
84:                                     :CA   => stroke_opacity,
85:                                     :ca   => opacity
86:                                     )
87: 
88:           dictionary_name = "Tr#{next_opacity_dictionary_id}"
89:           opacity_dictionary_registry[key] = { :name => dictionary_name, 
90:                                                :obj  => dictionary }
91:         end
92: 
93:         page.ext_gstates.merge!(dictionary_name => dictionary)
94:         dictionary_name
95:       end

opacity_dictionary_registry() click to toggle source

    # File lib/prawn/graphics/transparency.rb, line 68
68:       def opacity_dictionary_registry
69:         @opacity_dictionary_registry ||= {}
70:       end

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Prawn::Graphics::Transparency

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