private void HuffmanEncode(ref List<byte> bits, int[,] block8, HuffmanTable huffmanDC, HuffmanTable huffmanAC, int DCIndex) {
short diff = (short)(block8[0, 0] - LastDC[DCIndex]);
LastDC[DCIndex] += diff;
if (diff != 0) {
byte category = bitCost(diff);
huffmanElement huffmanCode = huffmanDC.getHuffmanCode(0, category);
ushortToBits(ref bits, huffmanCode.codeWord, huffmanCode.length);
ushortToBits(ref bits, negativeNumberEncoder(diff), category);
} else {
huffmanElement EOB = huffmanDC.getHuffmanCode(0x00, 0x00);
ushortToBits(ref bits, EOB.codeWord, EOB.length);
}
int zeroesCounter = 0;
for (int i = 1; i < 64; i++) {
int x = _roadPoints[i, 0], y = _roadPoints[i, 1];
if (block8[x, y] == 0) {
zeroesCounter++;
continue;
}
while (zeroesCounter >= 16) {
huffmanElement ZRL = huffmanAC.getHuffmanCode(0x0F, 0x00);
ushortToBits(ref bits, ZRL.codeWord, ZRL.length);
zeroesCounter -= 16;
}
byte cost = bitCost((short)Math.Abs(block8[x, y]));
huffmanElement codeElement = huffmanAC.getHuffmanCode((byte)zeroesCounter, cost);
zeroesCounter = 0;
ushortToBits(ref bits, codeElement.codeWord, codeElement.length);
ushortToBits(ref bits, negativeNumberEncoder((short)block8[x, y]), cost);
}
if (zeroesCounter != 0) { //EOB
huffmanElement EOB = huffmanAC.getHuffmanCode(0x00, 0x00);
ushortToBits(ref bits, EOB.codeWord, EOB.length);
}
}
private void addHuffmanTable(HuffmanTable huffman, byte id, bool dc) {
writeBytesToStream(0xff, 0xc4); //DHT marker
ushort len = (ushort)(huffman.combinationsInTable + 19);
writeBytesToStream((byte)(len >> 8), (byte)(len & 0xff));
byte combined;
if (!dc) {
combined = (byte)((1 << 4) + id);
} else {
combined = id;
}
writeBytesToStream(combined);
for (int i = 0; i < 16; i++) {
writeBytesToStream(huffman.bitLengths[i]);
}
for (int i = 0; i < 16; i++) {
for (int j = 0; j < huffman.combinationsInTable; j++) {
if (huffman.elements[j].length == i + 1) {
writeBytesToStream(huffman.elements[j].runSize);
}
}
}
}