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# frozen_string_literal: true
# blend_mode.rb : Implements blend modes
#
# Contributed by John Ford. October, 2015
#
# This is free software. Please see the LICENSE and COPYING files for details.
#
module Prawn
module Graphics
# The Prawn::BlendMode module is used to change the way
# two layers are blended together.
#
# Passing an array of blend modes is allowed. PDF viewers should
# blend layers based on the first recognized blend mode.
#
# Valid blend modes in v1.4 of the PDF spec include :Normal, :Multiply,
# :Screen, :Overlay, :Darken, :Lighten, :ColorDodge, :ColorBurn, :HardLight,
# :SoftLight, :Difference, :Exclusion, :Hue, :Saturation, :Color, and
# :Luminosity.
#
# Example:
# pdf.fill_color('0000ff')
# pdf.fill_rectangle([x, y+25], 50, 50)
# pdf.blend_mode(:Multiply) do
# pdf.fill_color('ff0000')
# pdf.fill_circle([x, y], 25)
# end
#
module BlendMode
# @group Stable API
def blend_mode(blend_mode = :Normal)
renderer.min_version(1.4)
save_graphics_state if block_given?
renderer.add_content "/#{blend_mode_dictionary_name(blend_mode)} gs"
if block_given?
yield
restore_graphics_state
end
end
private
def blend_mode_dictionary_registry
@blend_mode_dictionary_registry ||= {}
end
def blend_mode_dictionary_name(blend_mode)
key = Array(blend_mode).join('')
dictionary_name = "BM#{key}"
dictionary = blend_mode_dictionary_registry[dictionary_name] ||= ref!(
Type: :ExtGState,
BM: blend_mode
)
page.ext_gstates[dictionary_name] = dictionary
dictionary_name
end
end
end
end
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