public virtual void Extract(sbyte[] segmentBytes, Com.Drew.Metadata.Metadata metadata, JpegSegmentType segmentType)
{
if (metadata.ContainsDirectory <JpegDirectory>())
{
// If this directory is already present, discontinue this operation.
// We only store metadata for the *first* matching SOFn segment.
return;
}
JpegDirectory directory = metadata.GetOrCreateDirectory <JpegDirectory>();
// The value of TAG_COMPRESSION_TYPE is determined by the segment type found
directory.SetInt(JpegDirectory.TagCompressionType, segmentType.byteValue - JpegSegmentType.Sof0.byteValue);
SequentialReader reader = new SequentialByteArrayReader(segmentBytes);
try
{
directory.SetInt(JpegDirectory.TagDataPrecision, reader.GetUInt8());
directory.SetInt(JpegDirectory.TagImageHeight, reader.GetUInt16());
directory.SetInt(JpegDirectory.TagImageWidth, reader.GetUInt16());
short componentCount = reader.GetUInt8();
directory.SetInt(JpegDirectory.TagNumberOfComponents, componentCount);
// for each component, there are three bytes of data:
// 1 - Component ID: 1 = Y, 2 = Cb, 3 = Cr, 4 = I, 5 = Q
// 2 - Sampling factors: bit 0-3 vertical, 4-7 horizontal
// 3 - Quantization table number
for (int i = 0; i < (int)componentCount; i++)
{
int componentId = reader.GetUInt8();
int samplingFactorByte = reader.GetUInt8();
int quantizationTableNumber = reader.GetUInt8();
JpegComponent component = new JpegComponent(componentId, samplingFactorByte, quantizationTableNumber);
directory.SetObject(JpegDirectory.TagComponentData1 + i, component);
}
}
catch (IOException ex)
{
directory.AddError(ex.Message);
}
}
