/// <summary>
/// Decodes a DXT1-compressed 4x4 block of texels using a prebuilt 4-color color table.
/// </summary>
/// <remarks>See https://msdn.microsoft.com/en-us/library/windows/desktop/bb694531(v=vs.85).aspx#BC1 </remarks>
static Color32[] DecodeDXT1TexelBlock(UnityBinaryReader r, Color[] colorTable)
{
Debug.Assert(colorTable.Length == 4);
// Read pixel color indices.
var colorIndices = new uint[16];
var colorIndexBytes = new byte[4];
r.Read(colorIndexBytes, 0, colorIndexBytes.Length);
const uint bitsPerColorIndex = 2;
for (uint rowIndex = 0; rowIndex < 4; rowIndex++)
{
var rowBaseColorIndexIndex = 4 * rowIndex;
var rowBaseBitOffset = 8 * rowIndex;
for (uint columnIndex = 0; columnIndex < 4; columnIndex++)
{
// Color indices are arranged from right to left.
var bitOffset = rowBaseBitOffset + (bitsPerColorIndex * (3 - columnIndex));
colorIndices[rowBaseColorIndexIndex + columnIndex] = (uint)Utils.GetBits(bitOffset, bitsPerColorIndex, colorIndexBytes);
}
}
// Calculate pixel colors.
var colors = new Color32[16];
for (var i = 0; i < 16; i++)
{
colors[i] = colorTable[colorIndices[i]];
}
return(colors);
}
/// <summary>
/// Decodes a DXT1-compressed 4x4 block of texels using a prebuilt 4-color color table.
/// </summary>
/// <remarks>See https://msdn.microsoft.com/en-us/library/windows/desktop/bb694531(v=vs.85).aspx#BC1 </remarks>
private static Color32[] DecodeDXT1TexelBlock(UnityBinaryReader reader, Color[] colorTable)
{
Debug.Assert(colorTable.Length == 4);
// Read pixel color indices.
//uint[] colorIndices = new uint[16];
//byte[] colorIndexBytes = new byte[4];
reader.Read(Dxt1colorIndexBytes, 0, Dxt1colorIndexBytes.Length);
const uint bitsPerColorIndex = 2;
uint rowIndex = 0;
uint columnIndex = 0;
uint rowBaseColorIndexIndex = 0;
uint rowBaseBitOffset = 0;
uint bitOffset = 0;
for (rowIndex = 0; rowIndex < 4; rowIndex++)
{
rowBaseColorIndexIndex = 4 * rowIndex;
rowBaseBitOffset = 8 * rowIndex;
for (columnIndex = 0; columnIndex < 4; columnIndex++)
{
// Color indices are arranged from right to left.
bitOffset = rowBaseBitOffset + (bitsPerColorIndex * (3 - columnIndex));
Dxt1colorIndices[rowBaseColorIndexIndex + columnIndex] = (uint)Utils.GetBits(bitOffset, bitsPerColorIndex, Dxt1colorIndexBytes);
}
}
// Calculate pixel colors.
//var colors = new Color32[16];
for (rowIndex = 0; rowIndex < 16; rowIndex++)
{
Dxt1Colors[rowIndex] = colorTable[Dxt1colorIndices[rowIndex]];
}
return(Dxt1Colors);
}
/// <summary>
/// Decodes a DXT5-compressed 4x4 block of texels.
/// </summary>
/// <remarks>See https://msdn.microsoft.com/en-us/library/windows/desktop/bb694531(v=vs.85).aspx#BC3 </remarks>
private static Color32[] DecodeDXT5TexelBlock(UnityBinaryReader reader)
{
// Create the alpha table.
var alphaTable = new float[8];
alphaTable[0] = reader.ReadByte();
alphaTable[1] = reader.ReadByte();
if (alphaTable[0] > alphaTable[1])
{
for (int i = 0; i < 6; i++)
{
alphaTable[2 + i] = Mathf.Lerp(alphaTable[0], alphaTable[1], (float)(1 + i) / 7);
}
}
else
{
for (int i = 0; i < 4; i++)
{
alphaTable[2 + i] = Mathf.Lerp(alphaTable[0], alphaTable[1], (float)(1 + i) / 5);
}
alphaTable[6] = 0;
alphaTable[7] = 255;
}
// Read pixel alpha indices.
var alphaIndices = new uint[16];
var alphaIndexBytesRow0 = new byte[3];
reader.Read(alphaIndexBytesRow0, 0, alphaIndexBytesRow0.Length);
Array.Reverse(alphaIndexBytesRow0); // Take care of little-endianness.
var alphaIndexBytesRow1 = new byte[3];
reader.Read(alphaIndexBytesRow1, 0, alphaIndexBytesRow1.Length);
Array.Reverse(alphaIndexBytesRow1); // Take care of little-endianness.
const uint bitsPerAlphaIndex = 3;
alphaIndices[0] = (uint)Utils.GetBits(21, bitsPerAlphaIndex, alphaIndexBytesRow0);
alphaIndices[1] = (uint)Utils.GetBits(18, bitsPerAlphaIndex, alphaIndexBytesRow0);
alphaIndices[2] = (uint)Utils.GetBits(15, bitsPerAlphaIndex, alphaIndexBytesRow0);
alphaIndices[3] = (uint)Utils.GetBits(12, bitsPerAlphaIndex, alphaIndexBytesRow0);
alphaIndices[4] = (uint)Utils.GetBits(9, bitsPerAlphaIndex, alphaIndexBytesRow0);
alphaIndices[5] = (uint)Utils.GetBits(6, bitsPerAlphaIndex, alphaIndexBytesRow0);
alphaIndices[6] = (uint)Utils.GetBits(3, bitsPerAlphaIndex, alphaIndexBytesRow0);
alphaIndices[7] = (uint)Utils.GetBits(0, bitsPerAlphaIndex, alphaIndexBytesRow0);
alphaIndices[8] = (uint)Utils.GetBits(21, bitsPerAlphaIndex, alphaIndexBytesRow1);
alphaIndices[9] = (uint)Utils.GetBits(18, bitsPerAlphaIndex, alphaIndexBytesRow1);
alphaIndices[10] = (uint)Utils.GetBits(15, bitsPerAlphaIndex, alphaIndexBytesRow1);
alphaIndices[11] = (uint)Utils.GetBits(12, bitsPerAlphaIndex, alphaIndexBytesRow1);
alphaIndices[12] = (uint)Utils.GetBits(9, bitsPerAlphaIndex, alphaIndexBytesRow1);
alphaIndices[13] = (uint)Utils.GetBits(6, bitsPerAlphaIndex, alphaIndexBytesRow1);
alphaIndices[14] = (uint)Utils.GetBits(3, bitsPerAlphaIndex, alphaIndexBytesRow1);
alphaIndices[15] = (uint)Utils.GetBits(0, bitsPerAlphaIndex, alphaIndexBytesRow1);
// Create the color table.
var colorTable = new Color[4];
colorTable[0] = ColorUtils.R5G6B5ToColor(reader.ReadLEUInt16());
colorTable[1] = ColorUtils.R5G6B5ToColor(reader.ReadLEUInt16());
colorTable[2] = Color.Lerp(colorTable[0], colorTable[1], 1.0f / 3);
colorTable[3] = Color.Lerp(colorTable[0], colorTable[1], 2.0f / 3);
// Calculate pixel colors.
var colors = DecodeDXT1TexelBlock(reader, colorTable);
for (int i = 0; i < 16; i++)
{
colors[i].a = (byte)Mathf.Round(alphaTable[alphaIndices[i]]);
}
return(colors);
}
/// <summary>
/// Decodes a DXT5-compressed 4x4 block of texels.
/// </summary>
/// <remarks>See https://msdn.microsoft.com/en-us/library/windows/desktop/bb694531(v=vs.85).aspx#BC3 </remarks>
private static Color32[] DecodeDXT5TexelBlock(UnityBinaryReader reader)
{
// Create the alpha table.
var alphaTable = new float[8];
alphaTable[0] = reader.ReadByte();
alphaTable[1] = reader.ReadByte();
if(alphaTable[0] > alphaTable[1])
{
for(int i = 0; i < 6; i++)
{
alphaTable[2 + i] = Mathf.Lerp(alphaTable[0], alphaTable[1], (float)(1 + i) / 7);
}
}
else
{
for(int i = 0; i < 4; i++)
{
alphaTable[2 + i] = Mathf.Lerp(alphaTable[0], alphaTable[1], (float)(1 + i) / 5);
}
alphaTable[6] = 0;
alphaTable[7] = 255;
}
// Read pixel alpha indices.
var alphaIndices = new uint[16];
var alphaIndexBytesRow0 = new byte[3];
reader.Read(alphaIndexBytesRow0, 0, alphaIndexBytesRow0.Length);
Array.Reverse(alphaIndexBytesRow0); // Take care of little-endianness.
var alphaIndexBytesRow1 = new byte[3];
reader.Read(alphaIndexBytesRow1, 0, alphaIndexBytesRow1.Length);
Array.Reverse(alphaIndexBytesRow1); // Take care of little-endianness.
const uint bitsPerAlphaIndex = 3;
alphaIndices[0] = (uint)Utils.GetBits(21, bitsPerAlphaIndex, alphaIndexBytesRow0);
alphaIndices[1] = (uint)Utils.GetBits(18, bitsPerAlphaIndex, alphaIndexBytesRow0);
alphaIndices[2] = (uint)Utils.GetBits(15, bitsPerAlphaIndex, alphaIndexBytesRow0);
alphaIndices[3] = (uint)Utils.GetBits(12, bitsPerAlphaIndex, alphaIndexBytesRow0);
alphaIndices[4] = (uint)Utils.GetBits(9, bitsPerAlphaIndex, alphaIndexBytesRow0);
alphaIndices[5] = (uint)Utils.GetBits(6, bitsPerAlphaIndex, alphaIndexBytesRow0);
alphaIndices[6] = (uint)Utils.GetBits(3, bitsPerAlphaIndex, alphaIndexBytesRow0);
alphaIndices[7] = (uint)Utils.GetBits(0, bitsPerAlphaIndex, alphaIndexBytesRow0);
alphaIndices[8] = (uint)Utils.GetBits(21, bitsPerAlphaIndex, alphaIndexBytesRow1);
alphaIndices[9] = (uint)Utils.GetBits(18, bitsPerAlphaIndex, alphaIndexBytesRow1);
alphaIndices[10] = (uint)Utils.GetBits(15, bitsPerAlphaIndex, alphaIndexBytesRow1);
alphaIndices[11] = (uint)Utils.GetBits(12, bitsPerAlphaIndex, alphaIndexBytesRow1);
alphaIndices[12] = (uint)Utils.GetBits(9, bitsPerAlphaIndex, alphaIndexBytesRow1);
alphaIndices[13] = (uint)Utils.GetBits(6, bitsPerAlphaIndex, alphaIndexBytesRow1);
alphaIndices[14] = (uint)Utils.GetBits(3, bitsPerAlphaIndex, alphaIndexBytesRow1);
alphaIndices[15] = (uint)Utils.GetBits(0, bitsPerAlphaIndex, alphaIndexBytesRow1);
// Create the color table.
var colorTable = new Color[4];
colorTable[0] = ColorUtils.R5G6B5ToColor(reader.ReadLEUInt16());
colorTable[1] = ColorUtils.R5G6B5ToColor(reader.ReadLEUInt16());
colorTable[2] = Color.Lerp(colorTable[0], colorTable[1], 1.0f / 3);
colorTable[3] = Color.Lerp(colorTable[0], colorTable[1], 2.0f / 3);
// Calculate pixel colors.
var colors = DecodeDXT1TexelBlock(reader, colorTable);
for(int i = 0; i < 16; i++)
{
colors[i].a = (byte)Mathf.Round(alphaTable[alphaIndices[i]]);
}
return colors;
}
/// <summary>
/// Decodes a DXT1-compressed 4x4 block of texels using a prebuilt 4-color color table.
/// </summary>
/// <remarks>See https://msdn.microsoft.com/en-us/library/windows/desktop/bb694531(v=vs.85).aspx#BC1 </remarks>
private static Color32[] DecodeDXT1TexelBlock(UnityBinaryReader reader, Color[] colorTable)
{
Debug.Assert(colorTable.Length == 4);
// Read pixel color indices.
var colorIndices = new uint[16];
var colorIndexBytes = new byte[4];
reader.Read(colorIndexBytes, 0, colorIndexBytes.Length);
const uint bitsPerColorIndex = 2;
for(uint rowIndex = 0; rowIndex < 4; rowIndex++)
{
var rowBaseColorIndexIndex = 4 * rowIndex;
var rowBaseBitOffset = 8 * rowIndex;
for(uint columnIndex = 0; columnIndex < 4; columnIndex++)
{
// Color indices are arranged from right to left.
var bitOffset = rowBaseBitOffset + (bitsPerColorIndex * (3 - columnIndex));
colorIndices[rowBaseColorIndexIndex + columnIndex] = (uint)Utils.GetBits(bitOffset, bitsPerColorIndex, colorIndexBytes);
}
}
// Calculate pixel colors.
var colors = new Color32[16];
for(int i = 0; i < 16; i++)
{
colors[i] = colorTable[colorIndices[i]];
}
return colors;
}