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JBIG2 - arithmetic decoder bugfixing

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This commit is contained in:
Jakub Melka
2019-10-29 15:34:09 +01:00
parent 34371706aa
commit 489033c4ce
4 changed files with 89 additions and 14 deletions
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41
PdfForQtLib/sources/pdfjbig2decoder.cpp
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@ -351,11 +351,23 @@ static constexpr PDFJBIG2ArithmeticDecoderQeValue JBIG2_ARITHMETIC_DECODER_QE_VA
{ 0x56010000, 46, 46, 0 }
};
uint32_t PDFJBIG2ArithmeticDecoder::readByte(size_t context, PDFJBIG2ArithmeticDecoderState* state)
{
uint32_t byte = 0;
for (int i = 0; i < 8; ++i)
{
byte = (byte << 1) | readBit(context, state);
}
return byte;
}
void PDFJBIG2ArithmeticDecoder::perform_INITDEC()
{
// Used figure G.1, in annex G, of specification
uint32_t B = m_reader->readUnsignedByte();
m_c = (B ^ 0xFF) << 16;
m_lastByte = B;
m_c = B << 16;
perform_BYTEIN();
m_c = m_c << 7;
m_ct -= 7;
@ -365,24 +377,26 @@ void PDFJBIG2ArithmeticDecoder::perform_INITDEC()
void PDFJBIG2ArithmeticDecoder::perform_BYTEIN()
{
// Used figure G.3, in annex G, of specification
const uint32_t B = m_reader->readUnsignedByte();
if (B == 0xFF)
if (m_lastByte == 0xFF)
{
const uint32_t B1 = m_reader->look(8);
if (B1 > 0x8F)
{
m_c += 0xFF00;
m_ct = 8;
}
else
{
m_c = m_c + (0xFE00 - (B << 9));
m_c = m_c + (B1 << 9);
m_ct = 7;
m_reader->readUnsignedByte();
m_lastByte = m_reader->readUnsignedByte();
}
}
else
{
m_c = m_c + (0xFF00 - (B << 8));
const uint32_t B = m_reader->readUnsignedByte();
m_lastByte = B;
m_c = m_c + (B << 8);
m_ct = 8;
}
}
@ -402,8 +416,11 @@ uint32_t PDFJBIG2ArithmeticDecoder::perform_DECODE(size_t context, PDFJBIG2Arith
const uint32_t Qe = QeInfo.Qe;
m_a -= Qe;
if (m_c < m_a)
if (m_c >= Qe)
{
// We are substracting this value according figure E.15 in the specification
m_c -= Qe;
if ((m_a & 0x80000000) == 0)
{
// We must perform MPS_EXCHANGE algorithm, according to figure E.16, in annex E, of specification
@ -430,9 +447,6 @@ uint32_t PDFJBIG2ArithmeticDecoder::perform_DECODE(size_t context, PDFJBIG2Arith
}
else
{
m_c -= m_a;
m_a = Qe;
// We must perform LPS_EXCHANGE algorithm, according to figure E.17, in annex E, of specification
if (m_a < Qe)
{
@ -447,6 +461,8 @@ uint32_t PDFJBIG2ArithmeticDecoder::perform_DECODE(size_t context, PDFJBIG2Arith
}
state->setQeRowIndexAndMPS(context, QeInfo.newLPS, MPS);
}
m_a = Qe;
}
// Perform RENORMD algorithm, according to figure E.18, in annex E, of specification
@ -1454,4 +1470,9 @@ std::vector<PDFJBIG2HuffmanTableEntry> PDFJBIG2HuffmanCodeTable::buildPrefixes(c
return result;
}
uint32_t PDFJBIG2ArithmeticDecoderState::getQe(size_t context) const
{
return JBIG2_ARITHMETIC_DECODER_QE_VALUES[getQeRowIndex(context)].Qe;
}
} // namespace pdf