public Color[] Decompress(byte[] blockData)
{
Debug.Assert(blockData.Length == BlockFormat.BC3ByteSize);
var block = BC3BlockData.FromBytes(blockData);
var colorTable = BC1ColorTable.Create(block.Color0, block.Color1);
var alphaTable = CreateAlphaTable(block.Alpha0, block.Alpha1);
var colors = new Color[BlockFormat.TexelCount];
for (int i = 0; i < colors.Length; ++i)
{
int colorIndex = block.ColorIndexes[i];
int alphaIndex = block.AlphaIndexes[i];
var color = colorTable[colorIndex];
var alpha = alphaTable[alphaIndex];
colors[i] = Color.FromArgb(alpha, ColorUtility.To32Bit(color));
}
return(colors);
}
/// <summary>
/// Instantiates a <see cref="BC3BlockData"/> from compressed BC3 block data.
/// </summary>
/// <param name="bytes">The data of a BC3 compressed block.</param>
public static BC3BlockData FromBytes(byte[] bytes)
{
Debug.Assert(bytes.Length == BlockFormat.BC3ByteSize,
"Mismatching number of bytes for format.");
byte alpha0 = bytes[0];
byte alpha1 = bytes[1];
byte[] alphas = new byte[6];
alphas[2] = bytes[2];
alphas[1] = bytes[3];
alphas[0] = bytes[4];
alphas[5] = bytes[5];
alphas[4] = bytes[6];
alphas[3] = bytes[7];
byte c0Low = bytes[8];
byte c0Hi = bytes[9];
byte c1Low = bytes[10];
byte c1Hi = bytes[11];
byte[] indexes = new byte[4];
indexes[0] = bytes[12];
indexes[1] = bytes[13];
indexes[2] = bytes[14];
indexes[3] = bytes[15];
var block = new BC3BlockData();
block.Alpha0 = alpha0;
block.Alpha1 = alpha1;
block.Color0 = Color565.FromValue((ushort)((c0Hi << 8) | c0Low));
block.Color1 = Color565.FromValue((ushort)((c1Hi << 8) | c1Low));
block.AlphaIndexes[0] = alphas[0] & 0x07; // xxxx x111
block.AlphaIndexes[1] = (alphas[0] >> 3) & 0x07; // xx11 1xxx
block.AlphaIndexes[2] = ((alphas[0] >> 6) & 0x03) | // 11xx xxxx LSB
((alphas[1] & 0x01) << 2); // xxxx xxx1 MSB
block.AlphaIndexes[3] = (alphas[1] >> 1) & 0x07; // xxxx 111x
block.AlphaIndexes[4] = (alphas[1] >> 4) & 0x07; // x111 xxxx
block.AlphaIndexes[5] = ((alphas[1] >> 7) & 0x01) | // 1xxx xxxx LSB
((alphas[2] & 0x03) << 1); // xxxx xx11 MSB
block.AlphaIndexes[6] = (alphas[2] >> 2) & 0x07; // xxx1 11xx
block.AlphaIndexes[7] = (alphas[2] >> 5) & 0x07; // 111x xxxx
block.AlphaIndexes[8] = alphas[3] & 0x07; // xxxx x111
block.AlphaIndexes[9] = (alphas[3] >> 3) & 0x07; // xx11 1xxx
block.AlphaIndexes[10] = ((alphas[3] >> 6) & 0x03) | // 11xx xxxx LSB
((alphas[4] & 0x01) << 2); // xxxx xxx1 MSB
block.AlphaIndexes[11] = (alphas[4] >> 1) & 0x07; // xxxx 111x
block.AlphaIndexes[12] = (alphas[4] >> 4) & 0x07; // x111 xxxx
block.AlphaIndexes[13] = ((alphas[4] >> 7) & 0x01) | // 1xxx xxxx LSB
((alphas[5] & 0x03) << 1); // xxxx xx11 MSB
block.AlphaIndexes[14] = (alphas[5] >> 2) & 0x07; // xxx1 11xx
block.AlphaIndexes[15] = (alphas[5] >> 5) & 0x07; // 111x xxxx
for (int p = 0, row = 0; p < BlockFormat.TexelCount; p += BlockFormat.Dimension, ++row)
{
int a = p;
int b = p + 1;
int c = p + 2;
int d = p + 3;
block.ColorIndexes[a] = indexes[row] & 0x03;
block.ColorIndexes[b] = (indexes[row] >> 2) & 0x03;
block.ColorIndexes[c] = (indexes[row] >> 4) & 0x03;
block.ColorIndexes[d] = (indexes[row] >> 6) & 0x03;
}
return(block);
}
