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# -*- encoding: utf-8; frozen_string_literal: true -*-
#
#--
# This file is part of HexaPDF.
#
# HexaPDF - A Versatile PDF Creation and Manipulation Library For Ruby
# Copyright (C) 2014-2019 Thomas Leitner
#
# HexaPDF is free software: you can redistribute it and/or modify it
# under the terms of the GNU Affero General Public License version 3 as
# published by the Free Software Foundation with the addition of the
# following permission added to Section 15 as permitted in Section 7(a):
# FOR ANY PART OF THE COVERED WORK IN WHICH THE COPYRIGHT IS OWNED BY
# THOMAS LEITNER, THOMAS LEITNER DISCLAIMS THE WARRANTY OF NON
# INFRINGEMENT OF THIRD PARTY RIGHTS.
#
# HexaPDF is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
# FITNESS FOR A PARTICULAR PURPOSE. See the GNU Affero General Public
# License for more details.
#
# You should have received a copy of the GNU Affero General Public License
# along with HexaPDF. If not, see <http://www.gnu.org/licenses/>.
#
# The interactive user interfaces in modified source and object code
# versions of HexaPDF must display Appropriate Legal Notices, as required
# under Section 5 of the GNU Affero General Public License version 3.
#
# In accordance with Section 7(b) of the GNU Affero General Public
# License, a covered work must retain the producer line in every PDF that
# is created or manipulated using HexaPDF.
#
# If the GNU Affero General Public License doesn't fit your need,
# commercial licenses are available at <https://gettalong.at/hexapdf/>.
#++
require 'fiber'
require 'hexapdf/error'
require 'hexapdf/configuration'
require 'hexapdf/utils/bit_stream'
module HexaPDF
module Filter
# Implements the predictor for the LZWDecode and FlateDecode filters.
#
# Although a predictor isn't a full PDF filter, it is implemented as one in HexaPDF terms to
# allow easy chaining of the predictor.
#
# See: PDF1.7 s7.4.4.3, s7.4.4.4, https://partners.adobe.com/public/developer/en/tiff/TIFF6.pdf
# (p64f), http://www.w3.org/TR/PNG-Filters.html
#
#-- Implemenation notes:
#
# The TIFF encoding and decoding methods are the same, except for the innermost loop. The way
# it is implemented is probably not the best but it avoids duplicate code.
#
# The situation is similar with PNG encoding and decoding.
#++
module Predictor
PREDICTOR_PNG_NONE = 0 #:nodoc:
PREDICTOR_PNG_SUB = 1 #:nodoc:
PREDICTOR_PNG_UP = 2 #:nodoc:
PREDICTOR_PNG_AVERAGE = 3 #:nodoc:
PREDICTOR_PNG_PAETH = 4 #:nodoc:
PREDICTOR_PNG_OPTIMUM = 5 #:nodoc:
# See HexaPDF::Filter
def self.decoder(source, options)
execute(:decoder, source, options)
end
# See HexaPDF::Filter
def self.encoder(source, options)
execute(:encoder, source, options)
end
def self.execute(type, source, options) # :nodoc:
return source if !options[:Predictor] || options[:Predictor] == 1
colors = options[:Colors] || 1
bits_per_component = options[:BitsPerComponent] || 8
columns = options[:Columns] || 1
if options[:Predictor] == 2
tiff_execute(type, source, colors, bits_per_component, columns)
elsif options[:Predictor] >= 10
png_execute(type, source, options[:Predictor], colors, bits_per_component, columns)
else
raise HexaPDF::InvalidPDFObjectError, "Predictor key is invalid: #{options[:Predictor]}"
end
end
def self.tiff_execute(type, source, colors, bits_per_component, columns) # :nodoc:
Fiber.new do
bytes_per_row = (columns * bits_per_component * colors + 7) / 8
mask = (1 << bits_per_component) - 1
data = ''.b
writer = HexaPDF::Utils::BitStreamWriter.new
pos = 0
decode_row = lambda do |result, reader|
last_components = [0] * colors
(columns * colors).times do |i|
i %= colors
tmp = (reader.read(bits_per_component) + last_components[i]) & mask
result << writer.write(tmp, bits_per_component)
last_components[i] = tmp
end
result << writer.finalize
end
encode_row = lambda do |result, reader|
last_components = [0] * colors
(columns * colors).times do |i|
i %= colors
tmp = reader.read(bits_per_component)
result << writer.write((tmp - last_components[i]) & mask, bits_per_component)
last_components[i] = tmp
end
result << writer.finalize
end
row_action = (type == :decoder ? decode_row : encode_row)
while source.alive? && (new_data = source.resume)
data.slice!(0...pos)
data << new_data
result = ''.b
pos = 0
while pos + bytes_per_row <= data.length
reader = HexaPDF::Utils::BitStreamReader.new(data[pos, bytes_per_row])
row_action.call(result, reader)
pos += bytes_per_row
end
Fiber.yield(result) unless result.empty?
end
unless pos == data.length
raise FilterError, "Data is missing for TIFF predictor"
end
end
end
def self.png_execute(type, source, predictor, colors, bits_per_component, columns) # :nodoc:
Fiber.new do
bytes_per_pixel = (bits_per_component * colors + 7) / 8
bytes_per_row = (columns * bits_per_component * colors + 7) / 8
bytes_per_row += 1 if type == :decoder
# Only on encoding: Arbitrarily choose a predictor if we should choose the optimum
predictor = predictor == 15 ? PREDICTOR_PNG_PAETH : predictor - 10
data = ''.b
last_line = "\0".b * (bytes_per_row + 1)
pos = 0
decode_row = lambda do |result|
line = data[pos + 1, bytes_per_row - 1]
case data.getbyte(pos)
when PREDICTOR_PNG_SUB
bytes_per_pixel.upto(bytes_per_row - 2) do |i|
line.setbyte(i, (line.getbyte(i) + line.getbyte(i - bytes_per_pixel)) % 256)
end
when PREDICTOR_PNG_UP
0.upto(bytes_per_row - 2) do |i|
line.setbyte(i, (line.getbyte(i) + last_line.getbyte(i)) % 256)
end
when PREDICTOR_PNG_AVERAGE
0.upto(bytes_per_row - 2) do |i|
a = i < bytes_per_pixel ? 0 : line.getbyte(i - bytes_per_pixel)
line.setbyte(i, (line.getbyte(i) + ((a + last_line.getbyte(i)) >> 1)) % 256)
end
when PREDICTOR_PNG_PAETH
0.upto(bytes_per_row - 2) do |i|
a = i < bytes_per_pixel ? 0 : line.getbyte(i - bytes_per_pixel)
b = last_line.getbyte(i)
c = i < bytes_per_pixel ? 0 : last_line.getbyte(i - bytes_per_pixel)
point = a + b - c
pa = (point - a).abs
pb = (point - b).abs
pc = (point - c).abs
point = ((pa <= pb && pa <= pc) ? a : (pb <= pc ? b : c))
line.setbyte(i, (line.getbyte(i) + point) % 256)
end
end
result << line
last_line = line
end
encode_row = lambda do |result|
line = predictor.chr.force_encoding(Encoding::BINARY) << data[pos, bytes_per_row]
next_last_line = line.dup
case predictor
when PREDICTOR_PNG_SUB
bytes_per_row.downto(bytes_per_pixel + 1) do |i|
line.setbyte(i, (line.getbyte(i) - line.getbyte(i - bytes_per_pixel)) % 256)
end
when PREDICTOR_PNG_UP
bytes_per_row.downto(1) do |i|
line.setbyte(i, (line.getbyte(i) - last_line.getbyte(i)) % 256)
end
when PREDICTOR_PNG_AVERAGE
bytes_per_row.downto(1) do |i|
a = i <= bytes_per_pixel ? 0 : line.getbyte(i - bytes_per_pixel)
line.setbyte(i, (line.getbyte(i) - ((a + last_line.getbyte(i)) >> 1)) % 256)
end
when PREDICTOR_PNG_PAETH
bytes_per_row.downto(1) do |i|
a = i <= bytes_per_pixel ? 0 : line.getbyte(i - bytes_per_pixel)
b = last_line.getbyte(i)
c = i <= bytes_per_pixel ? 0 : last_line.getbyte(i - bytes_per_pixel)
point = a + b - c
pa = (point - a).abs
pb = (point - b).abs
pc = (point - c).abs
point = ((pa <= pb && pa <= pc) ? a : (pb <= pc ? b : c))
line.setbyte(i, (line.getbyte(i) - point) % 256)
end
end
result << line
last_line = next_last_line
end
row_action = (type == :decoder ? decode_row : encode_row)
while source.alive? && (new_data = source.resume)
data.slice!(0...pos)
data << new_data
result = ''.b
pos = 0
while pos + bytes_per_row <= data.length
row_action.call(result)
pos += bytes_per_row
end
Fiber.yield(result) unless result.empty?
end
if pos != data.length && GlobalConfiguration['filter.predictor.strict']
raise FilterError, "Data is missing for PNG predictor"
elsif pos != data.length && data.length != 1
result = ''.b
bytes_per_row = data.length - pos
row_action.call(result)
result
end
end
end
end
end
end
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