public Color[] Decompress(byte[] blockData)
{
Debug.Assert(blockData.Length == BlockFormat.BC2ByteSize);
var block = BC2BlockData.FromBytes(blockData);
var colorTable = BC1ColorTable.Create(block.Color0, block.Color1);
var colors = new Color[BlockFormat.TexelCount];
for (int i = 0; i < colors.Length; ++i)
{
int index = block.ColorIndexes[i];
int alpha = block.ColorAlphas[i];
// Convert 4-bit alpha to 8-bit by shifting the bits left and ORing
// with the most significant bits to calculate the remaining values
alpha = (alpha << 4) | (alpha & 0x0F);
var color16 = colorTable[index];
var color32 = Color.FromArgb(alpha, ColorUtility.To32Bit(color16));
colors[i] = color32;
}
return(colors);
}
public byte[] Compress(Color[] colors)
{
Debug.Assert(colors.Length == BlockFormat.TexelCount);
var colorSpace = new ColorSpace(colors);
var colorTable = BC1ColorTable.Create(colorSpace.MaxColor, colorSpace.MinColor);
// Interpolate 6 alpha values by passing max alpha as alpha0
var alphaTable = CreateAlphaTable(colorSpace.MaxAlpha, colorSpace.MinAlpha);
var block = new BC3BlockData();
block.Color0 = colorTable[0];
block.Color1 = colorTable[1];
block.Alpha0 = alphaTable[0];
block.Alpha1 = alphaTable[1];
for (int i = 0; i < colors.Length; ++i)
{
var color32 = colors[i];
var color16 = ColorUtility.To16Bit(color32);
block.ColorIndexes[i] = ColorUtility.GetIndexOfClosestColor(colorTable, color16);
block.AlphaIndexes[i] = ColorUtility.GetIndexOfClosestAlpha(alphaTable, color32.A);
}
return(block.ToBytes());
}
/// <summary>
/// Creates a BC1 color table from the 32-bit colors of a block. If the color space
/// contains alpha values, the color table is built according to BC1 1-bit alpha
/// specification.
/// </summary>
private static Color565[] CreateColorTable(Color[] colors)
{
var colorSpace = new ColorSpace(colors);
return(colorSpace.HasAlpha?
BC1ColorTable.CreateFor1BitAlpha(colorSpace.MinColor, colorSpace.MaxColor) :
BC1ColorTable.Create(colorSpace.MaxColor, colorSpace.MinColor));
}
public byte[] Compress(Color[] colors)
{
Debug.Assert(colors.Length == BlockFormat.TexelCount);
var colorSpace = new ColorSpace(colors);
var colorTable = BC1ColorTable.Create(colorSpace.MaxColor, colorSpace.MinColor);
var block = new BC2BlockData();
block.Color0 = colorTable[0];
block.Color1 = colorTable[1];
for (int i = 0; i < colors.Length; ++i)
{
var color32 = colors[i];
var color16 = ColorUtility.To16Bit(color32);
block.ColorIndexes[i] = ColorUtility.GetIndexOfClosestColor(colorTable, color16);
block.ColorAlphas[i] = color32.A >> 4; // Convert 8-bit alpha to 4-bit
}
return(block.ToBytes());
}
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>
/// Creates a BC1 color table from two compressed 16-bit reference colors.
/// If the integer value of <paramref name="color0"/> is lower or equal to
/// that of <paramref name="color1"/>, the color table is built according
/// to the 1-bit alpha specification.
/// </summary>
private static Color565[] CreateColorTable(Color565 color0, Color565 color1)
{
return(color0.Value <= color1.Value ?
BC1ColorTable.CreateFor1BitAlpha(color0, color1) :
BC1ColorTable.Create(color0, color1));
}
