private ExifValue CreateValue()
{
if (!_reader.CanRead(12))
{
return(null);
}
var tag = (ExifTagValue)ReadShort();
var dataType = EnumHelper.Parse(ReadShort(), ExifDataType.Unknown);
ExifValue value = null;
if (dataType == ExifDataType.Unknown)
{
return(null);
}
var numberOfComponents = ReadLong();
if (dataType == ExifDataType.Undefined && numberOfComponents == 0)
{
numberOfComponents = 4;
}
var oldIndex = _reader.Index;
var length = numberOfComponents * ExifDataTypes.GetSize(dataType);
if (length <= 4)
{
value = CreateValue(tag, dataType, numberOfComponents);
}
else
{
var newIndex = _startIndex + ReadLong();
if (_reader.Seek(newIndex) && _reader.CanRead(length))
{
value = CreateValue(tag, dataType, numberOfComponents);
}
}
if (value == null)
{
InvalidTags.Add(new UnkownExifTag(tag));
}
_reader.Seek(oldIndex + 4);
return(value);
}
public void Read(byte[] data)
{
Values.Clear();
InvalidTags.Clear();
if (data == null || data.Length == 0)
{
return;
}
_reader = new EndianReader(data);
if (_reader.ReadString(4) == "Exif")
{
if (_reader.ReadShortMSB() != 0)
{
return;
}
_startIndex = 6;
}
_isLittleEndian = _reader.ReadString(2) == "II";
if (ReadShort() != 0x002A)
{
return;
}
var ifdOffset = ReadLong();
AddValues(Values, ifdOffset);
var thumbnailOffset = ReadLong();
ReadThumbnail(thumbnailOffset);
if (_exifOffset != 0)
{
AddValues(Values, _exifOffset);
}
if (_gpsOffset != 0)
{
AddValues(Values, _gpsOffset);
}
}
