Class: Pdfrb::Document::GraphicsState

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

Overview

Facade for managing ExtGState (graphics state) entries on pages. Each page can reference a /ExtGState sub-dict in /Resources that holds named graphics-state parameter sets (transparency, line width, overprint, etc.).

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(document) ⇒ GraphicsState

Returns a new instance of GraphicsState.



12
13
14
15
 
# File 'lib/pdfrb/document/graphics_state.rb', line 12

def initialize(document)
  @document = document
  @next_gs_number = 1
end

Instance Attribute Details

#document ⇒ Object (readonly)

Returns the value of attribute document.



10
11
12
 
# File 'lib/pdfrb/document/graphics_state.rb', line 10

def document
  @document
end

Instance Method Details

#count(page) ⇒ Object 



65
66
67
 
# File 'lib/pdfrb/document/graphics_state.rb', line 65

def count(page)
  each(page).count
end

#each(page, &block) ⇒ Object

Enumerate ExtGState entries on a page.



53
54
55
56
57
58
59
60
61
62
63
 
# File 'lib/pdfrb/document/graphics_state.rb', line 53

def each(page, &block)
  return enum_for(:each, page) unless block

  resources = page_resources(page)
  return unless resources

  ext = resources.value[:ExtGState]
  return unless ext

  ext.each(&block)
end

#register(page, **params) ⇒ Symbol

Register an ExtGState parameter dict on a page and return the resource name (e.g., :GS1).

Parameters:

  • page (Pdfrb::Model::Type::Page) —

    target page.

  • params (Hash) —

    graphics state parameters (e.g., { CA: 0.5, ca: 0.5 } for 50% stroke + fill alpha).

Returns:

  • (Symbol) —

    resource name.



24
25
26
27
28
29
30
31
32
33
34
35
 
# File 'lib/pdfrb/document/graphics_state.rb', line 24

def register(page, **params)
  gs = document.add({ Type: :ExtGState, **params },
                    type: Pdfrb::Model::Type::GraphicsStateParameter)
  ref = Pdfrb::Model::Reference.new(gs.oid, gs.gen)

  resources = ensure_resources(page)
  ext_gstate = resources.value[:ExtGState] || {}
  name = gs_name
  ext_gstate[name] = ref
  resources.value[:ExtGState] = ext_gstate
  name
end

#register_line_width(page, width:, line_cap: nil, line_join: nil) ⇒ Object

Convenience: register a line-width state.



45
46
47
48
49
50
 
# File 'lib/pdfrb/document/graphics_state.rb', line 45

def register_line_width(page, width:, line_cap: nil, line_join: nil)
  params = { LW: width }
  params[:LC] = line_cap if line_cap
  params[:LJ] = line_join if line_join
  register(page, **params)
end

#register_transparency(page, opacity:, blend_mode: nil) ⇒ Object

Convenience: register a transparency state.



38
39
40
41
42
 
# File 'lib/pdfrb/document/graphics_state.rb', line 38

def register_transparency(page, opacity:, blend_mode: nil)
  params = { ca: opacity, CA: opacity }
  params[:BM] = blend_mode if blend_mode
  register(page, **params)
end