/// <summary>
/// Initializes a new instance of the <see cref="OrigJpegDecoderCore" /> class.
/// </summary>
/// <param name="configuration">The configuration.</param>
/// <param name="options">The options.</param>
public OrigJpegDecoderCore(Configuration configuration, IJpegDecoderOptions options)
{
this.IgnoreMetadata = options.IgnoreMetadata;
this.configuration = configuration ?? Configuration.Default;
this.HuffmanTrees = OrigHuffmanTree.CreateHuffmanTrees();
this.QuantizationTables = new Block8x8F[MaxTq + 1];
this.Temp = new byte[2 * Block8x8F.Size];
}
/// <summary>
/// Read metadata from stream and read the blocks in the scans into <see cref="OrigComponent.SpectralBlocks"/>.
/// </summary>
/// <param name="stream">The stream</param>
/// <param name="metadataOnly">Whether to decode metadata only.</param>
public void ParseStream(Stream stream, bool metadataOnly = false)
{
this.MetaData = new ImageMetaData();
this.InputStream = stream;
this.InputProcessor = new InputProcessor(stream, this.Temp);
if (!metadataOnly)
{
this.HuffmanTrees = OrigHuffmanTree.CreateHuffmanTrees();
this.QuantizationTables = new Block8x8F[MaxTq + 1];
}
// Check for the Start Of Image marker.
this.InputProcessor.ReadFull(this.Temp, 0, 2);
if (this.Temp[0] != OrigJpegConstants.Markers.XFF || this.Temp[1] != OrigJpegConstants.Markers.SOI)
{
throw new ImageFormatException("Missing SOI marker.");
}
// Process the remaining segments until the End Of Image marker.
bool processBytes = true;
// we can't currently short circute progressive images so don't try.
while (processBytes)
{
this.InputProcessor.ReadFull(this.Temp, 0, 2);
if (this.InputProcessor.ReachedEOF)
{
// We've reached the end of the stream.
processBytes = false;
}
while (this.Temp[0] != 0xff)
{
// Strictly speaking, this is a format error. However, libjpeg is
// liberal in what it accepts. As of version 9, next_marker in
// jdmarker.c treats this as a warning (JWRN_EXTRANEOUS_DATA) and
// continues to decode the stream. Even before next_marker sees
// extraneous data, jpeg_fill_bit_buffer in jdhuff.c reads as many
// bytes as it can, possibly past the end of a scan's data. It
// effectively puts back any markers that it overscanned (e.g. an
// "\xff\xd9" EOI marker), but it does not put back non-marker data,
// and thus it can silently ignore a small number of extraneous
// non-marker bytes before next_marker has a chance to see them (and
// print a warning).
// We are therefore also liberal in what we accept. Extraneous data
// is silently ignore
// This is similar to, but not exactly the same as, the restart
// mechanism within a scan (the RST[0-7] markers).
// Note that extraneous 0xff bytes in e.g. SOS data are escaped as
// "\xff\x00", and so are detected a little further down below.
this.Temp[0] = this.Temp[1];
this.Temp[1] = this.InputProcessor.ReadByte();
}
byte marker = this.Temp[1];
if (marker == 0)
{
// Treat "\xff\x00" as extraneous data.
continue;
}
while (marker == 0xff)
{
// Section B.1.1.2 says, "Any marker may optionally be preceded by any
// number of fill bytes, which are bytes assigned code X'FF'".
this.InputProcessor.ReadByteUnsafe(out marker);
if (this.InputProcessor.ReachedEOF)
{
// We've reached the end of the stream.
processBytes = false;
break;
}
}
// End Of Image.
if (marker == OrigJpegConstants.Markers.EOI)
{
break;
}
if (marker >= OrigJpegConstants.Markers.RST0 && marker <= OrigJpegConstants.Markers.RST7)
{
// Figures B.2 and B.16 of the specification suggest that restart markers should
// only occur between Entropy Coded Segments and not after the final ECS.
// However, some encoders may generate incorrect JPEGs with a final restart
// marker. That restart marker will be seen here instead of inside the ProcessSOS
// method, and is ignored as a harmless error. Restart markers have no extra data,
// so we check for this before we read the 16-bit length of the segment.
continue;
}
// Read the 16-bit length of the segment. The value includes the 2 bytes for the
// length itself, so we subtract 2 to get the number of remaining bytes.
this.InputProcessor.ReadFullUnsafe(this.Temp, 0, 2);
int remaining = (this.Temp[0] << 8) + this.Temp[1] - 2;
if (remaining < 0)
{
throw new ImageFormatException("Short segment length.");
}
switch (marker)
{
case OrigJpegConstants.Markers.SOF0:
case OrigJpegConstants.Markers.SOF1:
case OrigJpegConstants.Markers.SOF2:
this.IsProgressive = marker == OrigJpegConstants.Markers.SOF2;
this.ProcessStartOfFrameMarker(remaining, metadataOnly);
break;
case OrigJpegConstants.Markers.DHT:
if (metadataOnly)
{
this.InputProcessor.Skip(remaining);
}
else
{
this.ProcessDefineHuffmanTablesMarker(remaining);
}
break;
case OrigJpegConstants.Markers.DQT:
if (metadataOnly)
{
this.InputProcessor.Skip(remaining);
}
else
{
this.ProcessDefineQuantizationTablesMarker(remaining);
}
break;
case OrigJpegConstants.Markers.SOS:
if (!metadataOnly)
{
this.ProcessStartOfScanMarker(remaining);
if (this.InputProcessor.ReachedEOF)
{
// If unexpected EOF reached. We can stop processing bytes as we now have the image data.
processBytes = false;
}
}
else
{
// It's highly unlikely that APPn related data will be found after the SOS marker
// We should have gathered everything we need by now.
processBytes = false;
}
break;
case OrigJpegConstants.Markers.DRI:
if (metadataOnly)
{
this.InputProcessor.Skip(remaining);
}
else
{
this.ProcessDefineRestartIntervalMarker(remaining);
}
break;
case OrigJpegConstants.Markers.APP0:
this.ProcessApplicationHeaderMarker(remaining);
break;
case OrigJpegConstants.Markers.APP1:
this.ProcessApp1Marker(remaining);
break;
case OrigJpegConstants.Markers.APP2:
this.ProcessApp2Marker(remaining);
break;
case OrigJpegConstants.Markers.APP14:
this.ProcessApp14Marker(remaining);
break;
default:
if ((marker >= OrigJpegConstants.Markers.APP0 && marker <= OrigJpegConstants.Markers.APP15) ||
marker == OrigJpegConstants.Markers.COM)
{
this.InputProcessor.Skip(remaining);
}
break;
}
}
this.InitDerivedMetaDataProperties();
}
