TIFF predictor

PdfForQtLib/sources/pdfimage.cpp

@@ -77,12 +77,12 @@ PDFImage PDFImage::createImage(const PDFDocument* document, const PDFStream* str
 
     if (isSoftMask && (imageMask || dictionary->hasKey("Mask") || dictionary->hasKey("SMask")))
     {
-        throw PDFRendererException(RenderErrorType::NotImplemented, PDFTranslationContext::tr("Soft mask image can't have mask / soft mask itself."));
+        throw PDFRendererException(RenderErrorType::Error, PDFTranslationContext::tr("Soft mask image can't have mask / soft mask itself."));
     }
 
     if (!isSoftMask && !matte.empty())
     {
-        throw PDFRendererException(RenderErrorType::NotImplemented, PDFTranslationContext::tr("Regular image can't have Matte entry (used for soft masks)."));
+        throw PDFRendererException(RenderErrorType::Error, PDFTranslationContext::tr("Regular image can't have Matte entry (used for soft masks)."));
     }
 
     // Fill Mask

PdfForQtLib/sources/pdfstreamfilters.cpp

@@ -800,9 +800,29 @@ QByteArray PDFStreamPredictor::applyTIFFPredictor(const QByteArray& data) const
 {
     Q_UNUSED(data);
 
-    // TODO: Implement TIFF algorithm filter
+    PDFBitWriter writer(m_bitsPerComponent);
-    throw PDFException(PDFTranslationContext::tr("Invalid predictor algorithm."));
+    PDFBitReader reader(&data, m_bitsPerComponent);
-    return QByteArray();
+
+    writer.reserve(data.size());
+    std::vector<uint32_t> leftValues(m_components, 0);
+
+    while (!reader.isAtEnd())
+    {
+        for (int i = 0; i < m_columns; ++i)
+        {
+            for (int componentIndex = 0; componentIndex < m_components; ++componentIndex)
+            {
+                leftValues[componentIndex] = (leftValues[componentIndex] + reader.read()) & reader.max();
+                writer.write(leftValues[componentIndex]);
+            }
+        }
+
+        std::fill(leftValues.begin(), leftValues.end(), 0);
+        reader.alignToBytes();
+        writer.finishLine();
+    }
+
+    return writer.takeByteArray();
 }
 
 QByteArray PDFCryptFilter::apply(const QByteArray& data,

PdfForQtLib/sources/pdfutils.cpp

@@ -84,4 +84,48 @@ bool PDFBitReader::isAtEnd() const
     return (m_position >= m_stream->size());
 }
 
+PDFBitWriter::PDFBitWriter(Value bitsPerComponent) :
+    m_bitsPerComponent(bitsPerComponent),
+    m_mask((static_cast<Value>(1) << m_bitsPerComponent) - static_cast<Value>(1)),
+    m_buffer(0),
+    m_bitsInBuffer(0)
+{
+
+}
+
+void PDFBitWriter::write(Value value)
+{
+    m_buffer = (m_buffer << m_bitsPerComponent) | (value & m_mask);
+    m_bitsInBuffer += m_bitsPerComponent;
+
+    flush(false);
+}
+
+void PDFBitWriter::flush(bool alignToByteBoundary)
+{
+    if (m_bitsInBuffer >= 8)
+    {
+        Value remainder = m_bitsInBuffer % 8;
+        Value alignedBuffer = m_buffer >> remainder;
+        Value bitsToWrite = m_bitsInBuffer - remainder;
+        Value bytesToWrite = bitsToWrite / 8;
+
+        for (Value byteIndex = 0; byteIndex < bytesToWrite; ++byteIndex)
+        {
+            const Value shift = (bytesToWrite - 1 - byteIndex) * 8;
+            m_outputByteArray.push_back(static_cast<const char>(static_cast<uint8_t>((alignedBuffer >> shift) & 0xFF)));
+        }
+
+        m_bitsInBuffer = remainder;
+    }
+
+    if (alignToByteBoundary && m_bitsInBuffer > 0)
+    {
+        Value missingBits = 8 - m_bitsInBuffer % 8;
+        m_buffer = m_buffer << missingBits;
+        m_bitsInBuffer += missingBits;
+        flush(false);
+    }
+}
+
 }   // namespace pdf

PdfForQtLib/sources/pdfutils.h

@@ -128,6 +128,37 @@ private:
     Value m_bitsInBuffer;
 };
 
+/// Bit writer
+class PDFBitWriter
+{
+public:
+    using Value = uint64_t;
+
+    explicit PDFBitWriter(Value bitsPerComponent);
+
+    /// Writes value to the output stream
+    void write(Value value);
+
+    /// Finish line - align to byte boundary
+    void finishLine() { flush(true); }
+
+    /// Returns the result byte array
+    QByteArray takeByteArray() { return qMove(m_outputByteArray); }
+
+    /// Reserve memory in buffer
+    void reserve(int size) { m_outputByteArray.reserve(size); }
+
+private:
+    void flush(bool alignToByteBoundary);
+
+    QByteArray m_outputByteArray;
+
+    Value m_bitsPerComponent;
+    Value m_mask;
+    Value m_buffer;
+    Value m_bitsInBuffer;
+};
+
 /// Simple class guard, for properly saving/restoring new/old value. In the constructor,
 /// new value is stored in the pointer (old one is being saved), and in the destructor,
 /// old value is restored. This object assumes, that value is not a null pointer.