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Finishing of CCITT fax filter

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This commit is contained in:
Jakub Melka
2019-10-18 14:36:28 +02:00
parent 9a59af2e12
commit a35957cb53
2 changed files with 41 additions and 8 deletions
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45
PdfForQtLib/sources/pdfccittfaxdecoder.cpp
View File

@ -354,7 +354,16 @@ PDFImageData PDFCCITTFaxDecoder::decode()
if (b2_index < referenceLine.size())
{
addPixels(codingLine, a0_index, referenceLine[b2_index], isCurrentPixelBlack, false);
if (referenceLine[b2_index] < m_parameters.columns)
{
b1_index += 2;
if (b1_index >= referenceLine.size())
{
throw PDFException(PDFTranslationContext::tr("Invalid pass encoding data in CCITT stream."));
}
}
}
else
{
@ -367,17 +376,22 @@ PDFImageData PDFCCITTFaxDecoder::decode()
case Horizontal:
{
// We scan two sequence length.
int a0a1 = getRunLength(!isCurrentPixelBlack);
int a1a2 = getRunLength(isCurrentPixelBlack);
const int a0a1 = getRunLength(!isCurrentPixelBlack);
const int a1a2 = getRunLength(isCurrentPixelBlack);
addPixels(codingLine, a0_index, codingLine[a0_index] + a0a1, isCurrentPixelBlack, false);
addPixels(codingLine, a0_index, codingLine[a0_index] + a1a2, !isCurrentPixelBlack, false);
while (referenceLine[b1_index] <= codingLine[a0_index] && b1_index < m_parameters.columns)
while (referenceLine[b1_index] <= codingLine[a0_index] && referenceLine[b1_index] < m_parameters.columns)
{
// We do not want to change the color (b1 should have opposite color of a0,
// should be first changing element of reference line right of a0).
b1_index += 2;
if (b1_index >= referenceLine.size())
{
throw PDFException(PDFTranslationContext::tr("Invalid horizontal encoding data in CCITT stream."));
}
}
break;
@ -398,18 +412,37 @@ PDFImageData PDFCCITTFaxDecoder::decode()
throw PDFException(PDFTranslationContext::tr("Invalid vertical encoding data in CCITT stream."));
}
addPixels(codingLine, a0_index, static_cast<uint32_t>(a1), isCurrentPixelBlack, mode < Vertical_0);
const bool isNegativeOffset = mode < Vertical_0;
addPixels(codingLine, a0_index, static_cast<uint32_t>(a1), isCurrentPixelBlack, isNegativeOffset);
isCurrentPixelBlack = !isCurrentPixelBlack;
if (codingLine[a0_index] < m_parameters.columns)
{
++b1_index;
// We must upgrade b1 index in such a way that it is first index
// of opposite color, than a0 index. If we are using negative offsets, then
// current position can move backward, and so we must look for first b1 index,
// which is of opposite color, than a0. So we decrease index by 1. But what to do,
// if we have b1 index equal to zero? In this case, we add -1 + 2 = 1 index, so we do it in
// same way, as positive/zero shift.
b1_index += (isNegativeOffset && b1_index > 0) ? -1 : 1;
while (referenceLine[b1_index] <= codingLine[a0_index] && b1_index < m_parameters.columns)
// Why we have this check, if same check is in while cycle? Because if we are adding
// to the b1_index, we can go outside of reference line range.
if (b1_index >= referenceLine.size())
{
throw PDFException(PDFTranslationContext::tr("Invalid vertical encoding data in CCITT stream."));
}
while (referenceLine[b1_index] <= codingLine[a0_index] && referenceLine[b1_index] < m_parameters.columns)
{
// We do not want to change the color (b1 should have opposite color of a0,
// should be first changing element of reference line right of a0).
b1_index += 2;
if (b1_index >= referenceLine.size())
{
throw PDFException(PDFTranslationContext::tr("Invalid vertical encoding data in CCITT stream."));
}
}
}

2
PdfForQtLib/sources/pdfutils.cpp
View File

@ -101,7 +101,7 @@ void PDFBitReader::alignToBytes()
bool PDFBitReader::isAtEnd() const
{
return (m_position >= m_stream->size());
return (m_position >= m_stream->size()) && m_bitsInBuffer == 0;
}
PDFBitWriter::PDFBitWriter(Value bitsPerComponent) :