Class: Preflight::Rules::NoTransparency

Inherits:
Object
  • Object
show all
Extended by:
Forwardable
Includes:
Measurements
Defined in:
lib/preflight/rules/no_transparency.rb

Overview

For some print workflows transparency is forbidden.

Arguments: none

Usage:

class MyPreflight
  include Preflight::Profile

  rule Preflight::Rules::NoTransparency
end

Instance Attribute Summary collapse

Instance Method Summary collapse

Instance Attribute Details

#issues ⇒ Object (readonly)

Returns the value of attribute issues.



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# File 'lib/preflight/rules/no_transparency.rb', line 30

def issues
  @issues
end

Instance Method Details

#detect_transparent_form(form) ⇒ Object

As each xobject is drawn on the canvas, record if it’s Group XObject with transparency



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# File 'lib/preflight/rules/no_transparency.rb', line 55

def detect_transparent_form(form)
  xobject = form.xobject
  group   = deref(xobject.hash[:Group])
  stype   = deref(group[:S])            if group

  if stype == :Transparency
    bbox = xobject.hash[:BBox] || @page.attributes[:MediaBox]
    bbox = translate_to_device_space(bbox)
    @issues << Issue.new("Transparent xobject found", self, :page         => @page.number,
                                                            :top_left     => bbox[:tl],
                                                            :bottom_left  => bbox[:bl],
                                                            :bottom_right => bbox[:br],
                                                            :top_right    => bbox[:tr])
  end
end

#invoke_xobject(label) ⇒ Object 



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# File 'lib/preflight/rules/no_transparency.rb', line 40

def invoke_xobject(label)
  @state.invoke_xobject(label) do |xobj|
    case xobj
    when PDF::Reader::FormXObject then
      detect_transparent_form(xobj)
      xobj.walk(self)
    else
      # TODO. can other xobjects have transparency?
    end
  end
end

#page=(page) ⇒ Object

we’re about to start a new page, reset state



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# File 'lib/preflight/rules/no_transparency.rb', line 34

def page=(page)
  @page   = page
  @state  = PDF::Reader::PageState.new(page)
  @issues = []
end