Class: HexaPDF::CLI::Images::ImageLocationProcessor

Inherits:
HexaPDF::Content::Processor show all
Defined in:
lib/hexapdf/cli/images.rb

Overview

Extracts the PPI (pixel per inch) information for each image of a content stream.

Constant Summary

Constants inherited from HexaPDF::Content::Processor

HexaPDF::Content::Processor::OPERATOR_MESSAGE_NAME_MAP

Instance Attribute Summary collapse

Attributes inherited from HexaPDF::Content::Processor

#graphics_object, #graphics_state, #operators, #resources

Instance Method Summary collapse

Methods inherited from HexaPDF::Content::Processor

#process

Constructor Details

#initialize(names, user_unit) ⇒ ImageLocationProcessor

Initialize the processor with the names of the images for which the PPI should be determined.



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# File 'lib/hexapdf/cli/images.rb', line 56

def initialize(names, user_unit)
  super()
  @names = names
  @user_unit = user_unit
  @result = {}
end

Instance Attribute Details

#result ⇒ Object (readonly)

The mapping of XObject name to [x_ppi, y_ppi].



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# File 'lib/hexapdf/cli/images.rb', line 52

def result
  @result
end

Instance Method Details

#paint_xobject(name) ⇒ Object

Determine the PPI in x- and y-directions of the specified images.

Raises:

  • (StopIteration) 


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# File 'lib/hexapdf/cli/images.rb', line 64

def paint_xobject(name)
  super
  return unless @names.delete(name)
  xobject = resources.xobject(name)
  return unless xobject[:Subtype] == :Image

  w, h = xobject.width, xobject.height
  llx, lly = graphics_state.ctm.evaluate(0, 0).map {|i| i * @user_unit }
  lrx, lry = graphics_state.ctm.evaluate(1, 0).map {|i| i * @user_unit }
  ulx, uly = graphics_state.ctm.evaluate(0, 1).map {|i| i * @user_unit }

  x_ppi = 72.0 * w / Math.sqrt((lrx - llx)**2 + (lry - lly)**2)
  y_ppi = 72.0 * h / Math.sqrt((ulx - llx)**2 + (uly - lly)**2)
  @result[name] = [x_ppi.round, y_ppi.round]
  raise StopIteration if @names.empty?
end