public static void DecodeIntegerSequence(
List <IntegerEncoded> DecodeIntegerSequence,
BitArrayStream BitStream,
int MaxRange,
int NumberValues)
{
// Determine encoding parameters
IntegerEncoded IntEncoded = CreateEncoding(MaxRange);
// Start decoding
int NumberValuesDecoded = 0;
while (NumberValuesDecoded < NumberValues)
{
switch (IntEncoded.GetEncoding())
{
case EIntegerEncoding.Quint:
{
DecodeQuintBlock(BitStream, DecodeIntegerSequence, IntEncoded.NumberBits);
NumberValuesDecoded += 3;
break;
}
case EIntegerEncoding.Trit:
{
DecodeTritBlock(BitStream, DecodeIntegerSequence, IntEncoded.NumberBits);
NumberValuesDecoded += 5;
break;
}
case EIntegerEncoding.JustBits:
{
IntEncoded.BitValue = BitStream.ReadBits(IntEncoded.NumberBits);
DecodeIntegerSequence.Add(IntEncoded);
NumberValuesDecoded++;
break;
}
}
}
}
static void DecodeColorValues(
int[] OutputValues,
byte[] InputData,
uint[] Modes,
int NumberPartitions,
int NumberBitsForColorData)
{
// First figure out how many color values we have
int NumberValues = 0;
for (int i = 0; i < NumberPartitions; i++)
{
NumberValues += (int)((Modes[i] >> 2) + 1) << 1;
}
// Then based on the number of values and the remaining number of bits,
// figure out the max value for each of them...
int Range = 256;
while (--Range > 0)
{
IntegerEncoded IntEncoded = IntegerEncoded.CreateEncoding(Range);
int BitLength = IntEncoded.GetBitLength(NumberValues);
if (BitLength <= NumberBitsForColorData)
{
// Find the smallest possible range that matches the given encoding
while (--Range > 0)
{
IntegerEncoded NewIntEncoded = IntegerEncoded.CreateEncoding(Range);
if (!NewIntEncoded.MatchesEncoding(IntEncoded))
{
break;
}
}
// Return to last matching range.
Range++;
break;
}
}
// We now have enough to decode our integer sequence.
List <IntegerEncoded> IntegerEncodedSequence = new List <IntegerEncoded>();
BitArrayStream ColorBitStream = new BitArrayStream(new BitArray(InputData));
IntegerEncoded.DecodeIntegerSequence(IntegerEncodedSequence, ColorBitStream, Range, NumberValues);
// Once we have the decoded values, we need to dequantize them to the 0-255 range
// This procedure is outlined in ASTC spec C.2.13
int OutputIndices = 0;
foreach (IntegerEncoded IntEncoded in IntegerEncodedSequence)
{
int BitLength = IntEncoded.NumberBits;
int BitValue = IntEncoded.BitValue;
Debug.Assert(BitLength >= 1);
int A = 0, B = 0, C = 0, D = 0;
// A is just the lsb replicated 9 times.
A = BitArrayStream.Replicate(BitValue & 1, 1, 9);
switch (IntEncoded.GetEncoding())
{
case IntegerEncoded.EIntegerEncoding.JustBits:
{
OutputValues[OutputIndices++] = BitArrayStream.Replicate(BitValue, BitLength, 8);
break;
}
case IntegerEncoded.EIntegerEncoding.Trit:
{
D = IntEncoded.TritValue;
switch (BitLength)
{
case 1:
{
C = 204;
break;
}
case 2:
{
C = 93;
// B = b000b0bb0
int b = (BitValue >> 1) & 1;
B = (b << 8) | (b << 4) | (b << 2) | (b << 1);
break;
}
case 3:
{
C = 44;
// B = cb000cbcb
int cb = (BitValue >> 1) & 3;
B = (cb << 7) | (cb << 2) | cb;
break;
}
case 4:
{
C = 22;
// B = dcb000dcb
int dcb = (BitValue >> 1) & 7;
B = (dcb << 6) | dcb;
break;
}
case 5:
{
C = 11;
// B = edcb000ed
int edcb = (BitValue >> 1) & 0xF;
B = (edcb << 5) | (edcb >> 2);
break;
}
case 6:
{
C = 5;
// B = fedcb000f
int fedcb = (BitValue >> 1) & 0x1F;
B = (fedcb << 4) | (fedcb >> 4);
break;
}
default:
throw new ASTCDecoderException("Unsupported trit encoding for color values!");
}
break;
}
case IntegerEncoded.EIntegerEncoding.Quint:
{
D = IntEncoded.QuintValue;
switch (BitLength)
{
case 1:
{
C = 113;
break;
}
case 2:
{
C = 54;
// B = b0000bb00
int b = (BitValue >> 1) & 1;
B = (b << 8) | (b << 3) | (b << 2);
break;
}
case 3:
{
C = 26;
// B = cb0000cbc
int cb = (BitValue >> 1) & 3;
B = (cb << 7) | (cb << 1) | (cb >> 1);
break;
}
case 4:
{
C = 13;
// B = dcb0000dc
int dcb = (BitValue >> 1) & 7;
B = (dcb << 6) | (dcb >> 1);
break;
}
case 5:
{
C = 6;
// B = edcb0000e
int edcb = (BitValue >> 1) & 0xF;
B = (edcb << 5) | (edcb >> 3);
break;
}
default:
throw new ASTCDecoderException("Unsupported quint encoding for color values!");
}
break;
}
}
if (IntEncoded.GetEncoding() != IntegerEncoded.EIntegerEncoding.JustBits)
{
int T = D * C + B;
T ^= A;
T = (A & 0x80) | (T >> 2);
OutputValues[OutputIndices++] = T;
}
}
// Make sure that each of our values is in the proper range...
for (int i = 0; i < NumberValues; i++)
{
Debug.Assert(OutputValues[i] <= 255);
}
}
static int UnquantizeTexelWeight(IntegerEncoded IntEncoded)
{
int BitValue = IntEncoded.BitValue;
int BitLength = IntEncoded.NumberBits;
int A = BitArrayStream.Replicate(BitValue & 1, 1, 7);
int B = 0, C = 0, D = 0;
int Result = 0;
switch (IntEncoded.GetEncoding())
{
case IntegerEncoded.EIntegerEncoding.JustBits:
Result = BitArrayStream.Replicate(BitValue, BitLength, 6);
break;
case IntegerEncoded.EIntegerEncoding.Trit:
{
D = IntEncoded.TritValue;
Debug.Assert(D < 3);
switch (BitLength)
{
case 0:
{
int[] Results = { 0, 32, 63 };
Result = Results[D];
break;
}
case 1:
{
C = 50;
break;
}
case 2:
{
C = 23;
int b = (BitValue >> 1) & 1;
B = (b << 6) | (b << 2) | b;
break;
}
case 3:
{
C = 11;
int cb = (BitValue >> 1) & 3;
B = (cb << 5) | cb;
break;
}
default:
throw new ASTCDecoderException("Invalid trit encoding for texel weight");
}
break;
}
case IntegerEncoded.EIntegerEncoding.Quint:
{
D = IntEncoded.QuintValue;
Debug.Assert(D < 5);
switch (BitLength)
{
case 0:
{
int[] Results = { 0, 16, 32, 47, 63 };
Result = Results[D];
break;
}
case 1:
{
C = 28;
break;
}
case 2:
{
C = 13;
int b = (BitValue >> 1) & 1;
B = (b << 6) | (b << 1);
break;
}
default:
throw new ASTCDecoderException("Invalid quint encoding for texel weight");
}
break;
}
}
if (IntEncoded.GetEncoding() != IntegerEncoded.EIntegerEncoding.JustBits && BitLength > 0)
{
// Decode the value...
Result = D * C + B;
Result ^= A;
Result = (A & 0x20) | (Result >> 2);
}
Debug.Assert(Result < 64);
// Change from [0,63] to [0,64]
if (Result > 32)
{
Result += 1;
}
return(Result);
}