private static JpegHeader HeaderForMarker(ushort startCode, JpegHeader previousHeader)
{
switch (startCode)
{
case 0xFFD8: return(new JpegHeader(previousHeader, JpegHeaderName.StartOfImage));
case 0xFFD9: return(new JpegHeader(previousHeader, JpegHeaderName.EndOfImage));
case 0xFFDA: return(new JpegHeader(previousHeader, JpegHeaderName.StartOfScan));
case 0xFFE0: return(new ApplicationSegment0(previousHeader));
default:
return(null);
}
}
/// <summary>
/// Search for headers in the data and store the results.
/// </summary>
/// <param name="dataReader">the data to read the bytes and bits from</param>
public IResultNode DetectData(IDataReader dataReader, IDetectionProperties properties)
{
JpegHeader root = new JpegHeader(this);
using (JpegParser parser = new JpegParser(dataReader))
{
JpegHeader previousHeader = root;
ushort marker;
while ((marker = parser.NextMarker()) != 0)
{
JpegHeader header = HeaderForMarker(marker, previousHeader);
if (header != null && header.HeaderName == JpegHeaderName.StartOfImage && root.Children.Count > 0)
{
root.Children.Clear();
}
if (header != null && parser.Parse(header))
{
previousHeader = header;
if (IsFullFile(root))
{
break;
}
}
else
{
parser.DataReader.Position++;
}
}
}
if (dataReader.State == DataReaderState.Cancelled || !IsFullFile(root))
{
root = null;
}
else
{
properties.DataFormat = CodecID.Jpeg;
properties.IsFullFile = true;
}
return(root);
}
public ApplicationSegment0(JpegHeader previousHeader)
: base(previousHeader, JpegHeaderName.ApplicationSegment0)
{
}
private static bool IsFullFile(JpegHeader root)
{
return(root.FirstChild.HeaderName == JpegHeaderName.StartOfImage &&
root.LastChild.HeaderName == JpegHeaderName.EndOfImage &&
root.FindChild(JpegHeaderName.StartOfScan, true) != null);
}
