/// <summary>
/// Creates a list of Chunks containing the PNG keywords
/// </summary>
/// <returns>
/// A <see cref="ByteVector"/> with the list of chunks, or
/// or <see langword="null" /> if no PNG Keywords are contained.
/// </returns>
private ByteVector RenderKeywordChunks()
{
// Check, if PngTag is contained
PngTag png_tag = GetTag(TagTypes.Png, true) as PngTag;
if (png_tag == null)
{
return(null);
}
ByteVector chunks = new ByteVector();
foreach (KeyValuePair <string, string> keyword in png_tag)
{
ByteVector data = new ByteVector();
data.Add(keyword.Key);
data.Add("\0");
data.Add(keyword.Value);
chunks.Add(ByteVector.FromUInt((uint)data.Count));
chunks.Add(tEXt_CHUNK_TYPE);
chunks.Add(data);
chunks.Add(ComputeCRC(tEXt_CHUNK_TYPE, data));
}
return(chunks);
}
/// <summary>
/// Reads an iTXt Chunk from file. The current position must be set
/// to the start of the Chunk Data. Such a Chunk may contain XMP data
/// or translated keywords.
/// </summary>
/// <param name="data_length">
/// A <see cref="System.Int32"/> with the length of the Chunk Data.
/// </param>
//private void ReadiTXtChunk (int data_length)
//{
// long position = Tell;
// // iTXt Chunk
// //
// // N Bytes Keyword
// // 1 Byte Null Separator
// // 1 Byte Compression Flag (0 for uncompressed data)
// // 1 Byte Compression Method
// // N Bytes Language Tag
// // 1 Byte Null Separator
// // N Bytes Translated Keyword
// // 1 Byte Null Terminator
// // N Bytes Txt
// //
// // Followed by 4 Bytes CRC data
// ByteVector data = ReadChunkData (data_length);
// CheckCRC (iTXt_CHUNK_TYPE, data, ReadCRC ());
// // handle XMP, which has a fixed header
// if (data.StartsWith (XMP_CHUNK_HEADER)) {
// ImageTag.AddTag (new XmpTag (data.Mid (XMP_CHUNK_HEADER.Length).ToString (StringType.UTF8), this));
// AddMetadataBlock (position - 8, data_length + 8 + 4);
// return;
// }
// int terminator_index;
// string keyword = ReadKeyword (data, 0, out terminator_index);
// if (terminator_index + 2 >= data_length)
// throw new CorruptFileException ("Compression Flag and Compression Method byte expected");
// byte compression_flag = data[terminator_index + 1];
// byte compression_method = data[terminator_index + 2];
// //string language = ReadTerminatedString (data, terminator_index + 3, out terminator_index);
// //string translated_keyword = ReadTerminatedString (data, terminator_index + 1, out terminator_index);
// ByteVector txt_data = data.Mid (terminator_index + 1);
// if (compression_flag != 0x00) {
// txt_data = Decompress (compression_method, txt_data);
// // ignore unknown compression methods
// if (txt_data == null)
// return;
// }
// string value = txt_data.ToString ();
// PngTag png_tag = GetTag (TagTypes.Png, true) as PngTag;
// if (png_tag.GetKeyword (keyword) == null)
// png_tag.SetKeyword (keyword, value);
// AddMetadataBlock (position - 8, data_length + 8 + 4);
//}
/// <summary>
/// Reads an tEXt Chunk from file. The current position must be set
/// to the start of the Chunk Data. Such a Chunk contains plain
/// keywords.
/// </summary>
/// <param name="data_length">
/// A <see cref="System.Int32"/> with the length of the Chunk Data.
/// </param>
private void ReadtEXtChunk(int data_length)
{
long position = Tell;
// tEXt Chunk
//
// N Bytes Keyword
// 1 Byte Null Separator
// N Bytes Txt
//
// Followed by 4 Bytes CRC data
ByteVector data = ReadChunkData(data_length);
CheckCRC(tEXt_CHUNK_TYPE, data, ReadCRC());
int keyword_terminator;
string keyword = ReadKeyword(data, 0, out keyword_terminator);
string value = data.Mid(keyword_terminator + 1).ToString();
PngTag png_tag = GetTag(TagTypes.Png, true) as PngTag;
if (png_tag.GetKeyword(keyword) == null)
{
png_tag.SetKeyword(keyword, value);
}
AddMetadataBlock(position - 8, data_length + 8 + 4);
}
