internal static void ConvertToCanonicalCode(ref HuffmanTable huffmanTable)
{
int newCode = -1; // Para compensar con el incremento inicial dentro del for debajo
uint prevLength = 1;
uint newCodeIndex = 0;
huffmanTable.table = new List<CodeInfo>();
for (uint i = 0; i < huffmanTable.numSymbols.Length; i++)
{
uint codeLength = i + 1;
for (uint j = 0; j < huffmanTable.numSymbols[i]; j++)
{
CodeInfo code = new CodeInfo();
int difLengths = (int)(codeLength - prevLength);
newCode = (newCode + 1) << difLengths;
prevLength = codeLength;
code.code = (uint)newCode;
code.length = (byte)codeLength;
code.number = (ushort)huffmanTable.codes[newCodeIndex++];
huffmanTable.table.Add(code);
}
}
huffmanTable.maxCodeLength = (byte)prevLength;
}
internal static ushort ReadRunAmplitude(BitReader bReader, HuffmanTable table)
{
ushort code = bReader.Peek(table.maxCodeLength);
CodeInfo currentCode = table.preIndexTable[code];
bReader.Read(currentCode.length);
return currentCode.number;
}
public static int ReadTable(BinaryReader reader, ImgInfo imgInfo)
{
byte tableInfo = reader.ReadByte();
byte tableId = (byte)(tableInfo & 0x7); // Low 3 bits of tableInfo
int numCodes = 0;
if (tableId > 3)
{
throw new Exception("Invalid ID for huffman table");
}
if ((tableInfo & 0xe0) != 0) // High 3 bits of tableInfo must be zero
{
throw new Exception("Invalid huffman table");
}
var huffmanTable = new HuffmanTable
{
id = tableId,
type = (byte)((tableInfo >> 4) & 0x1), // Bit 4 of tableInfo
valid = true,
numSymbols = new byte[16]
};
for (int i = 0; i < 16; i++)
{
huffmanTable.numSymbols[i] = reader.ReadByte();
numCodes += huffmanTable.numSymbols[i];
}
huffmanTable.codes = new byte[numCodes];
for (int i = 0; i < numCodes; i++)
{
huffmanTable.codes[i] = reader.ReadByte();
}
Huffman.CreateTable(ref huffmanTable);
imgInfo.huffmanTables[huffmanTable.type, huffmanTable.id] = huffmanTable;
return(1 + 16 + numCodes);
}
public static int ReadTable(BinaryReader reader, ImgInfo imgInfo)
{
byte tableInfo = reader.ReadByte();
byte tableId = (byte)(tableInfo & 0x7); // Low 3 bits of tableInfo
int numCodes = 0;
if (tableId > 3)
throw new Exception("Invalid ID for huffman table");
if ((tableInfo & 0xe0) != 0) // High 3 bits of tableInfo must be zero
throw new Exception("Invalid huffman table");
var huffmanTable = new HuffmanTable();
huffmanTable.id = tableId;
huffmanTable.type = (byte)((tableInfo >> 4) & 0x1); // Bit 4 of tableInfo
huffmanTable.valid = true;
huffmanTable.numSymbols = new byte[16];
for (int i = 0; i < 16; i++)
{
huffmanTable.numSymbols[i] = reader.ReadByte();
numCodes += huffmanTable.numSymbols[i];
}
huffmanTable.codes = new byte[numCodes];
for (int i = 0; i < numCodes; i++)
{
huffmanTable.codes[i] = reader.ReadByte();
}
Huffman.CreateTable(ref huffmanTable);
imgInfo.huffmanTables[huffmanTable.type, huffmanTable.id] = huffmanTable;
Log(reader, huffmanTable);
return 1 + 16 + numCodes;
}
internal static void PreparePreindexedTables(ref HuffmanTable huffmanTable)
{
// Codigo de datos preindizados
// En esta parte, se construye una tabla de a que simbolos corresponden a cada codigo
// tomando en cuenta los bits posteriores del codigo siguiente, ya que se lee del stream
// un numero fijo de bits, esta misma tabla nos va a decir despues cuantos bits se van a extraer
// de la lectura hecha anteriormente
huffmanTable.preIndexTable = new CodeInfo[1U << huffmanTable.maxCodeLength];
foreach (var codeWord in huffmanTable.table)
{
int shift = huffmanTable.maxCodeLength - (int)codeWord.length;
uint numCodes = 1U << shift;
uint initialCode = codeWord.code << shift;
for (uint nextCode = initialCode; nextCode < (numCodes + initialCode); nextCode++)
{
huffmanTable.preIndexTable[nextCode] = codeWord;
}
}
}
internal static void CreateTable(ref HuffmanTable huffmanTable)
{
ConvertToCanonicalCode(ref huffmanTable);
PreparePreindexedTables(ref huffmanTable);
}
static void Log(BinaryReader reader, HuffmanTable huffmanTable)
{
Logger.WriteLine("Table ID: " + huffmanTable.id);
Logger.WriteLine("Type: " + huffmanTable.type);
Logger.WriteLine("Max code length: " + huffmanTable.maxCodeLength);
Logger.WriteLine("The table itself");
Common.PrintHuffmanTable(huffmanTable.table);
Logger.WriteLine("Total: " + huffmanTable.table.Count);
Logger.WriteLine();
}