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https://github.com/JakubMelka/PDF4QT.git
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JBIG2 - arithmetic decoder
This commit is contained in:
Jakub Melka
@@ -39,6 +39,7 @@ SOURCES += \
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sources/pdfblendfunction.cpp \
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sources/pdfccittfaxdecoder.cpp \
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sources/pdfitemmodels.cpp \
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sources/pdfjbig2decoder.cpp \
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sources/pdfobject.cpp \
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sources/pdfoptionalcontent.cpp \
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sources/pdfparser.cpp \
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@@ -69,6 +70,7 @@ HEADERS += \
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sources/pdfblendfunction.h \
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sources/pdfccittfaxdecoder.h \
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sources/pdfitemmodels.h \
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sources/pdfjbig2decoder.h \
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sources/pdfmeshqualitysettings.h \
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sources/pdfobject.h \
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sources/pdfoptionalcontent.h \
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202
PdfForQtLib/sources/pdfjbig2decoder.cpp
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202
PdfForQtLib/sources/pdfjbig2decoder.cpp
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@@ -0,0 +1,202 @@
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// Copyright (C) 2019 Jakub Melka
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//
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// This file is part of PdfForQt.
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//
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// PdfForQt is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// PdfForQt is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with PDFForQt. If not, see <https://www.gnu.org/licenses/>.
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#include "pdfjbig2decoder.h"
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namespace pdf
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{
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struct PDFJBIG2ArithmeticDecoderQeValue
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{
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uint32_t Qe; ///< Value of Qe
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uint8_t newMPS; ///< New row if MPS (more probable symbol)
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uint8_t newLPS; ///< New row if LPS (less probable symbol)
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uint8_t switchFlag; ///< Meaning of MPS/LPS is switched
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};
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static constexpr PDFJBIG2ArithmeticDecoderQeValue JBIG2_ARITHMETIC_DECODER_QE_VALUES[] =
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{
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{ 0x56010000, 1, 1, 1 },
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{ 0x34010000, 2, 6, 0 },
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{ 0x18010000, 3, 9, 0 },
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{ 0x0AC10000, 4, 12, 0 },
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{ 0x05210000, 5, 29, 0 },
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{ 0x02210000, 38, 33, 0 },
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{ 0x56010000, 7, 6, 1 },
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{ 0x54010000, 8, 14, 0 },
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{ 0x48010000, 9, 14, 0 },
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{ 0x38010000, 10, 14, 0 },
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{ 0x30010000, 11, 17, 0 },
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{ 0x24010000, 12, 18, 0 },
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{ 0x1C010000, 13, 20, 0 },
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{ 0x16010000, 29, 21, 0 },
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{ 0x56010000, 15, 14, 1 },
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{ 0x54010000, 16, 14, 0 },
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{ 0x51010000, 17, 15, 0 },
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{ 0x48010000, 18, 16, 0 },
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{ 0x38010000, 19, 17, 0 },
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{ 0x34010000, 20, 18, 0 },
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{ 0x30010000, 21, 19, 0 },
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{ 0x28010000, 22, 19, 0 },
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{ 0x24010000, 23, 20, 0 },
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{ 0x22010000, 24, 21, 0 },
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{ 0x1C010000, 25, 22, 0 },
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{ 0x18010000, 26, 23, 0 },
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{ 0x16010000, 27, 24, 0 },
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{ 0x14010000, 28, 25, 0 },
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{ 0x12010000, 29, 26, 0 },
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{ 0x11010000, 30, 27, 0 },
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{ 0x0AC10000, 31, 28, 0 },
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{ 0x09C10000, 32, 29, 0 },
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{ 0x08A10000, 33, 30, 0 },
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{ 0x05210000, 34, 31, 0 },
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{ 0x04410000, 35, 32, 0 },
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{ 0x02A10000, 36, 33, 0 },
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{ 0x02210000, 37, 34, 0 },
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{ 0x01410000, 38, 35, 0 },
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{ 0x01110000, 39, 36, 0 },
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{ 0x00850000, 40, 37, 0 },
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{ 0x00490000, 41, 38, 0 },
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{ 0x00250000, 42, 39, 0 },
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{ 0x00150000, 43, 40, 0 },
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{ 0x00090000, 44, 41, 0 },
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{ 0x00050000, 45, 42, 0 },
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{ 0x00010000, 45, 43, 0 },
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{ 0x56010000, 46, 46, 0 }
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};
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void PDFJBIG2ArithmeticDecoder::perform_INITDEC()
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{
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// Used figure G.1, in annex G, of specification
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uint32_t B = m_reader->read(8);
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m_c = (B ^ 0xFF) << 16;
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perform_BYTEIN();
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m_c = m_c << 7;
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m_ct -= 7;
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m_a = 0x80000000;
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}
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void PDFJBIG2ArithmeticDecoder::perform_BYTEIN()
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{
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// Used figure G.3, in annex G, of specification
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const uint32_t B = m_reader->read(8);
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if (B == 0xFF)
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{
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const uint32_t B1 = m_reader->look(8);
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if (B1 > 0x8F)
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{
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m_ct = 8;
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}
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else
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{
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m_c = m_c + (0xFE00 - (B << 9));
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m_ct = 7;
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m_reader->read(8);
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}
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}
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else
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{
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m_c = m_c + (0xFF00 - (B << 8));
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m_ct = 8;
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}
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}
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uint32_t PDFJBIG2ArithmeticDecoder::perform_DECODE(size_t context, PDFJBIG2ArithmeticDecoderState* state)
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{
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// Used figure G.2, in annex G, of specification
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const uint8_t QeRowIndex = state->getQeRowIndex(context);
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uint8_t MPS = state->getMPS(context);
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uint8_t D = MPS;
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// Sanity checks
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Q_ASSERT(QeRowIndex < std::size(JBIG2_ARITHMETIC_DECODER_QE_VALUES));
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Q_ASSERT(MPS < 2);
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const PDFJBIG2ArithmeticDecoderQeValue& QeInfo = JBIG2_ARITHMETIC_DECODER_QE_VALUES[QeRowIndex];
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const uint32_t Qe = QeInfo.Qe;
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m_a -= Qe;
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if (m_c < m_a)
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{
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if ((m_a & 0x80000000) == 0)
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{
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// We must perform MPS_EXCHANGE algorithm, according to figure E.16, in annex E, of specification
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if (m_a < Qe)
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{
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D = 1 - MPS;
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if (QeInfo.switchFlag)
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{
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MPS = 1 - MPS;
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}
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state->setQeRowIndexAndMPS(context, QeInfo.newLPS, MPS);
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}
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else
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{
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state->setQeRowIndexAndMPS(context, QeInfo.newMPS, MPS);
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}
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}
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else
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{
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// Do nothing, we are finished
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return D;
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}
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}
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else
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{
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m_c -= m_a;
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m_a = Qe;
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// We must perform LPS_EXCHANGE algorithm, according to figure E.17, in annex E, of specification
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if (m_a < Qe)
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{
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state->setQeRowIndexAndMPS(context, QeInfo.newMPS, MPS);
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}
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else
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{
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D = 1 - MPS;
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if (QeInfo.switchFlag)
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{
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MPS = 1 - MPS;
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}
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state->setQeRowIndexAndMPS(context, QeInfo.newLPS, MPS);
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}
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}
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// Perform RENORMD algorithm, according to figure E.18, in annex E, of specification
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do
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{
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if (m_ct == 0)
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{
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perform_BYTEIN();
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}
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m_a = m_a << 1;
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m_c = m_c << 1;
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--m_ct;
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}
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while ((m_a & 0x80000000) == 0);
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return D;
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}
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PDFJBIG2Decoder::PDFJBIG2Decoder()
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{
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}
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} // namespace pdf
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122
PdfForQtLib/sources/pdfjbig2decoder.h
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122
PdfForQtLib/sources/pdfjbig2decoder.h
Normal file
@@ -0,0 +1,122 @@
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// Copyright (C) 2019 Jakub Melka
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//
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// This file is part of PdfForQt.
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//
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// PdfForQt is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// PdfForQt is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with PDFForQt. If not, see <https://www.gnu.org/licenses/>.
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#ifndef PDFJBIG2DECODER_H
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#define PDFJBIG2DECODER_H
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#include "pdfutils.h"
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namespace pdf
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{
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/// Arithmetic decoder state for JBIG2 data streams. It contains state for context,
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/// state is stored as 8-bit value, where only 7 bits are used. 6 bits are used
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/// to store Qe value index (current row in the table, number 0-46), and lowest 1 bit
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/// is used to store current MPS value (most probable symbol - 0/1).
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class PDFJBIG2ArithmeticDecoderState
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{
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public:
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explicit inline PDFJBIG2ArithmeticDecoderState(size_t size) :
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m_state(size, 0)
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{
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}
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/// Returns row index to Qe value table, according to document ISO/IEC 14492:2001,
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/// annex E, table E.1 (Qe values and probability estimation process).
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inline uint8_t getQeRowIndex(size_t context) const
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{
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Q_ASSERT(context < m_state.size());
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return m_state[context] >> 1;
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}
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/// Returns current bit value of MPS (most probable symbol)
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inline uint8_t getMPS(size_t context) const
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{
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Q_ASSERT(context < m_state.size());
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return m_state[context] & 0x1;
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}
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/// Sets current row index to Qe value table, at given context, and also MPS bit value
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/// (most probable symbol).
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inline void setQeRowIndexAndMPS(size_t context, uint8_t QeRowIndex, uint8_t MPS)
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{
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Q_ASSERT(context < m_state.size());
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Q_ASSERT(MPS < 2);
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m_state[context] = (QeRowIndex << 1) + MPS;
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}
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private:
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std::vector<uint8_t> m_state;
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};
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/// Arithmetic decoder for JBIG2 data streams. This arithmetic decoder is implementation
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/// of decoder described in document ISO/IEC 14492:2001, T.88, annex G (arithmetic decoding
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/// procedure). It uses 32-bit fixed point arithmetic instead of 16-bit fixed point
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/// arithmetic described in the specification (it is much faster).
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class PDFJBIG2ArithmeticDecoder
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{
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public:
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explicit inline PDFJBIG2ArithmeticDecoder() :
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m_c(0),
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m_a(0),
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m_ct(0),
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m_reader(nullptr)
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{
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}
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void initialize() { perform_INITDEC(); }
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private:
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/// Performs INITDEC operation as described in the specification
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void perform_INITDEC();
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/// Performs BYTEIN operation as described in the specification
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void perform_BYTEIN();
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/// Performs DECODE operation as described in the specification
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/// \param context Context index
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/// \param state State of the arithmetic decoder
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/// \returns Single decoded bit (lowest bit, other bits are zero)
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uint32_t perform_DECODE(size_t context, PDFJBIG2ArithmeticDecoderState* state);
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/// This is 32 bit register consisting of two 16-bit subregisters - "c_high" and "c_low", as
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/// it is in specification. But we can work with it as 32 bit register (if we adjust some
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/// operations and fixed point arithmetic).
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uint32_t m_c;
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/// This is 32 bit register for interval range. In the specification, it is 16-bit register,
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/// but we use 32-bit fixed point arithmetic instead of 16-bit fixed point arithmetic.
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uint32_t m_a;
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/// Number of current unprocessed bits.
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uint32_t m_ct;
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/// Data source to read from
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PDFBitReader* m_reader;
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};
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class PDFJBIG2Decoder
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{
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public:
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PDFJBIG2Decoder();
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};
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} // namespace pdf
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#endif // PDFJBIG2DECODER_H
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