private static IReadOnlyList <XmpDirectory> ReadJpegSegments(IEnumerable <JpegSegment> segments)
{
// This is a modified version of XmpReader.ReadJpegSegments
// The original version specifically tests the buffer against the classic XMP preamble and discards everything else.
// Here we also test against the extended XMP preamble and regroup all the extended segments into a single buffer.
// Note that we do not import any of the usual tags as in ProcessXmpTags(). Users of the class have to go
// through XmpMeta methods.
var directories = new List <XmpDirectory>();
byte[] extendedData = null;
int maxPreambleLength = Math.Max(XmpJpegPreamble.Length, XmpJpegExtendedPreamble.Length);
try
{
foreach (var segment in segments)
{
string extractedPreamble = Encoding.UTF8.GetString(segment.Bytes, 0, maxPreambleLength);
if (extractedPreamble.StartsWith(XmpJpegPreamble))
{
ParseNormalXmpSegment(directories, segment.Bytes);
}
else if (extractedPreamble.StartsWith(XmpJpegExtendedPreamble))
{
ParseExtendedXmpSegment(ref extendedData, segment.Bytes);
}
}
}
catch (JpegProcessingException)
{
return(directories);
}
if (extendedData == null)
{
return(directories);
}
// We have collected extended XMP data, let's parse the reconstructed buffer.
XmpDirectory directory = new XmpDirectory();
try
{
var xmpMeta = XmpMetaFactory.ParseFromBuffer(extendedData);
directory.SetXmpMeta(xmpMeta);
}
catch (XmpException e)
{
directory.AddError("Error processing XMP data: " + e.Message);
}
directories.Add(directory);
return(directories);
}
private static void ParseNormalXmpSegment(List <XmpDirectory> directories, byte[] segmentBytes)
{
byte[] xmpBytes = new byte[segmentBytes.Length - XmpJpegPreamble.Length];
Array.Copy(segmentBytes, XmpJpegPreamble.Length, xmpBytes, 0, xmpBytes.Length);
XmpDirectory directory = new XmpDirectory();
try
{
var xmpMeta = XmpMetaFactory.ParseFromBuffer(xmpBytes);
directory.SetXmpMeta(xmpMeta);
}
catch (XmpException e)
{
directory.AddError("Error processing XMP data: " + e.Message);
}
directories.Add(directory);
}
