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#!/usr/bin/env ruby
# coding: utf-8
# This demonstrates a way to extract some images (those based on the JPG or
# TIFF formats) from a PDF. There are other ways to store images, so
# it may need to be expanded for real world usage, but it should serve
# as a good guide.
#
# Thanks to Jack Rusher for the initial version of this example.
require 'pdf/reader'
module ExtractImages
class Extractor
def page(page)
process_page(page, 0)
end
private
def complete_refs
@complete_refs ||= {}
end
def process_page(page, count)
xobjects = page.xobjects
return count if xobjects.empty?
xobjects.each do |name, stream|
case stream.hash[:Subtype]
when :Image then
count += 1
case stream.hash[:Filter]
when :CCITTFaxDecode then
ExtractImages::Tiff.new(stream).save("#{page.number}-#{count}-#{name}.tif")
when :DCTDecode then
ExtractImages::Jpg.new(stream).save("#{page.number}-#{count}-#{name}.jpg")
else
ExtractImages::Raw.new(stream).save("#{page.number}-#{count}-#{name}.tif")
end
when :Form then
count = process_page(PDF::Reader::FormXObject.new(page, stream), count)
end
end
count
end
end
class Raw
attr_reader :stream
def initialize(stream)
@stream = stream
end
def save(filename)
case @stream.hash[:ColorSpace]
when :DeviceCMYK then save_cmyk(filename)
when :DeviceGray then save_gray(filename)
when :DeviceRGB then save_rgb(filename)
else
$stderr.puts "unsupport color depth #{@stream.hash[:ColorSpace]} #{filename}"
end
end
private
def save_cmyk(filename)
h = stream.hash[:Height]
w = stream.hash[:Width]
bpc = stream.hash[:BitsPerComponent]
len = stream.hash[:Length]
puts "#{filename}: h=#{h}, w=#{w}, bpc=#{bpc}, len=#{len}"
# Synthesize a TIFF header
long_tag = lambda {|tag, count, value| [ tag, 4, count, value ].pack( "ssII" ) }
short_tag = lambda {|tag, count, value| [ tag, 3, count, value ].pack( "ssII" ) }
# header = byte order, version magic, offset of directory, directory count,
# followed by a series of tags containing metadata.
tag_count = 10
header = [ 73, 73, 42, 8, tag_count ].pack("ccsIs")
tiff = header.dup
tiff << short_tag.call( 256, 1, w ) # image width
tiff << short_tag.call( 257, 1, h ) # image height
tiff << long_tag.call( 258, 4, (header.size + (tag_count*12) + 4)) # bits per pixel
tiff << short_tag.call( 259, 1, 1 ) # compression
tiff << short_tag.call( 262, 1, 5 ) # colorspace - separation
tiff << long_tag.call( 273, 1, (10 + (tag_count*12) + 20) ) # data offset
tiff << short_tag.call( 277, 1, 4 ) # samples per pixel
tiff << long_tag.call( 279, 1, stream.unfiltered_data.size) # data byte size
tiff << short_tag.call( 284, 1, 1 ) # planer config
tiff << long_tag.call( 332, 1, 1) # inkset - CMYK
tiff << [0].pack("I") # next IFD pointer
tiff << [bpc, bpc, bpc, bpc].pack("IIII")
tiff << stream.unfiltered_data
File.open(filename, "wb") { |file| file.write tiff }
end
def save_gray(filename)
h = stream.hash[:Height]
w = stream.hash[:Width]
bpc = stream.hash[:BitsPerComponent]
len = stream.hash[:Length]
puts "#{filename}: h=#{h}, w=#{w}, bpc=#{bpc}, len=#{len}"
# Synthesize a TIFF header
long_tag = lambda {|tag, count, value| [ tag, 4, count, value ].pack( "ssII" ) }
short_tag = lambda {|tag, count, value| [ tag, 3, count, value ].pack( "ssII" ) }
# header = byte order, version magic, offset of directory, directory count,
# followed by a series of tags containing metadata.
tag_count = 9
header = [ 73, 73, 42, 8, tag_count ].pack("ccsIs")
tiff = header.dup
tiff << short_tag.call( 256, 1, w ) # image width
tiff << short_tag.call( 257, 1, h ) # image height
tiff << short_tag.call( 258, 1, 8 ) # bits per pixel
tiff << short_tag.call( 259, 1, 1 ) # compression
tiff << short_tag.call( 262, 1, 1 ) # colorspace - grayscale
tiff << long_tag.call( 273, 1, (10 + (tag_count*12) + 4) ) # data offset
tiff << short_tag.call( 277, 1, 1 ) # samples per pixel
tiff << long_tag.call( 279, 1, stream.unfiltered_data.size) # data byte size
tiff << short_tag.call( 284, 1, 1 ) # planer config
tiff << [0].pack("I") # next IFD pointer
p stream.unfiltered_data.size
tiff << stream.unfiltered_data
File.open(filename, "wb") { |file| file.write tiff }
end
def save_rgb(filename)
h = stream.hash[:Height]
w = stream.hash[:Width]
bpc = stream.hash[:BitsPerComponent]
len = stream.hash[:Length]
puts "#{filename}: h=#{h}, w=#{w}, bpc=#{bpc}, len=#{len}"
# Synthesize a TIFF header
long_tag = lambda {|tag, count, value| [ tag, 4, count, value ].pack( "ssII" ) }
short_tag = lambda {|tag, count, value| [ tag, 3, count, value ].pack( "ssII" ) }
# header = byte order, version magic, offset of directory, directory count,
# followed by a series of tags containing metadata.
tag_count = 8
header = [ 73, 73, 42, 8, tag_count ].pack("ccsIs")
tiff = header.dup
tiff << short_tag.call( 256, 1, w ) # image width
tiff << short_tag.call( 257, 1, h ) # image height
tiff << long_tag.call( 258, 3, (header.size + (tag_count*12) + 4)) # bits per pixel
tiff << short_tag.call( 259, 1, 1 ) # compression
tiff << short_tag.call( 262, 1, 2 ) # colorspace - RGB
tiff << long_tag.call( 273, 1, (header.size + (tag_count*12) + 16) ) # data offset
tiff << short_tag.call( 277, 1, 3 ) # samples per pixel
tiff << long_tag.call( 279, 1, stream.unfiltered_data.size) # data byte size
tiff << [0].pack("I") # next IFD pointer
tiff << [bpc, bpc, bpc].pack("III")
tiff << stream.unfiltered_data
File.open(filename, "wb") { |file| file.write tiff }
end
end
class Jpg
attr_reader :stream
def initialize(stream)
@stream = stream
end
def save(filename)
w = stream.hash[:Width]
h = stream.hash[:Height]
puts "#{filename}: h=#{h}, w=#{w}"
File.open(filename, "wb") { |file| file.write stream.data }
end
end
class Tiff
attr_reader :stream
def initialize(stream)
@stream = stream
end
def save(filename)
if stream.hash[:DecodeParms][:K] <= 0
save_group_four(filename)
else
$stderr.puts "#{filename}: CCITT non-group 4/2D image."
end
end
private
# Group 4, 2D
def save_group_four(filename)
k = stream.hash[:DecodeParms][:K]
h = stream.hash[:Height]
w = stream.hash[:Width]
bpc = stream.hash[:BitsPerComponent]
mask = stream.hash[:ImageMask]
len = stream.hash[:Length]
cols = stream.hash[:DecodeParms][:Columns]
puts "#{filename}: h=#{h}, w=#{w}, bpc=#{bpc}, mask=#{mask}, len=#{len}, cols=#{cols}, k=#{k}"
# Synthesize a TIFF header
long_tag = lambda {|tag, value| [ tag, 4, 1, value ].pack( "ssII" ) }
short_tag = lambda {|tag, value| [ tag, 3, 1, value ].pack( "ssII" ) }
# header = byte order, version magic, offset of directory, directory count,
# followed by a series of tags containing metadata: 259 is a magic number for
# the compression type; 273 is the offset of the image data.
tiff = [ 73, 73, 42, 8, 5 ].pack("ccsIs") \
+ short_tag.call( 256, cols ) \
+ short_tag.call( 257, h ) \
+ short_tag.call( 259, 4 ) \
+ long_tag.call( 273, (10 + (5*12) + 4) ) \
+ long_tag.call( 279, len) \
+ [0].pack("I") \
+ stream.data
File.open(filename, "wb") { |file| file.write tiff }
end
end
end
filename = File.expand_path(File.dirname(__FILE__)) + "/../spec/data/adobe_sample.pdf"
extractor = ExtractImages::Extractor.new
PDF::Reader.open(filename) do |reader|
page = reader.page(1)
extractor.page(page)
end
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