private static unsafe byte[] DecompressRXGB(DDSStruct header, byte[] data, PixelFormat pixelFormat)
{
// allocate bitmap
int bpp = (int)(Helper.PixelFormatToBpp(pixelFormat, header.pixelformat.rgbbitcount));
int bps = (int)(header.width * bpp * Helper.PixelFormatToBpc(pixelFormat));
int sizeofplane = (int)(bps * header.height);
int width = (int)header.width;
int height = (int)header.height;
int depth = (int)header.depth;
byte[] rawData = new byte[depth * sizeofplane + height * bps + width * bpp];
Colour565 color_0 = new Colour565();
Colour565 color_1 = new Colour565();
Colour8888[] colours = new Colour8888[4];
byte[] alphas = new byte[8];
fixed(byte *bytePtr = data)
{
byte *temp = bytePtr;
for (int z = 0; z < depth; z++)
{
for (int y = 0; y < height; y += 4)
{
for (int x = 0; x < width; x += 4)
{
if (y >= height || x >= width)
{
break;
}
alphas[0] = temp[0];
alphas[1] = temp[1];
byte *alphamask = temp + 2;
temp += 8;
Helper.DxtcReadColors(temp, ref color_0, ref color_1);
temp += 4;
uint bitmask = ((uint *)temp)[1];
temp += 4;
colours[0].red = (byte)(color_0.red << 3);
colours[0].green = (byte)(color_0.green << 2);
colours[0].blue = (byte)(color_0.blue << 3);
colours[0].alpha = 0xFF;
colours[1].red = (byte)(color_1.red << 3);
colours[1].green = (byte)(color_1.green << 2);
colours[1].blue = (byte)(color_1.blue << 3);
colours[1].alpha = 0xFF;
// Four-color block: derive the other two colors.
// 00 = color_0, 01 = color_1, 10 = color_2, 11 = color_3
// These 2-bit codes correspond to the 2-bit fields
// stored in the 64-bit block.
colours[2].blue = (byte)((2 * colours[0].blue + colours[1].blue + 1) / 3);
colours[2].green = (byte)((2 * colours[0].green + colours[1].green + 1) / 3);
colours[2].red = (byte)((2 * colours[0].red + colours[1].red + 1) / 3);
colours[2].alpha = 0xFF;
colours[3].blue = (byte)((colours[0].blue + 2 * colours[1].blue + 1) / 3);
colours[3].green = (byte)((colours[0].green + 2 * colours[1].green + 1) / 3);
colours[3].red = (byte)((colours[0].red + 2 * colours[1].red + 1) / 3);
colours[3].alpha = 0xFF;
int k = 0;
for (int j = 0; j < 4; j++)
{
for (int i = 0; i < 4; i++, k++)
{
int select = (int)((bitmask & (0x03 << k * 2)) >> k * 2);
Colour8888 col = colours[select];
// only put pixels out < width or height
if (((x + i) < width) && ((y + j) < height))
{
uint offset = (uint)(z * sizeofplane + (y + j) * bps + (x + i) * bpp);
rawData[offset + 0] = col.red;
rawData[offset + 1] = col.green;
rawData[offset + 2] = col.blue;
}
}
}
// 8-alpha or 6-alpha block?
if (alphas[0] > alphas[1])
{
// 8-alpha block: derive the other six alphas.
// Bit code 000 = alpha_0, 001 = alpha_1, others are interpolated.
alphas[2] = (byte)((6 * alphas[0] + 1 * alphas[1] + 3) / 7); // bit code 010
alphas[3] = (byte)((5 * alphas[0] + 2 * alphas[1] + 3) / 7); // bit code 011
alphas[4] = (byte)((4 * alphas[0] + 3 * alphas[1] + 3) / 7); // bit code 100
alphas[5] = (byte)((3 * alphas[0] + 4 * alphas[1] + 3) / 7); // bit code 101
alphas[6] = (byte)((2 * alphas[0] + 5 * alphas[1] + 3) / 7); // bit code 110
alphas[7] = (byte)((1 * alphas[0] + 6 * alphas[1] + 3) / 7); // bit code 111
}
else
{
// 6-alpha block.
// Bit code 000 = alpha_0, 001 = alpha_1, others are interpolated.
alphas[2] = (byte)((4 * alphas[0] + 1 * alphas[1] + 2) / 5); // Bit code 010
alphas[3] = (byte)((3 * alphas[0] + 2 * alphas[1] + 2) / 5); // Bit code 011
alphas[4] = (byte)((2 * alphas[0] + 3 * alphas[1] + 2) / 5); // Bit code 100
alphas[5] = (byte)((1 * alphas[0] + 4 * alphas[1] + 2) / 5); // Bit code 101
alphas[6] = 0x00; // Bit code 110
alphas[7] = 0xFF; // Bit code 111
}
// Note: Have to separate the next two loops,
// it operates on a 6-byte system.
// First three bytes
uint bits = *((uint *)alphamask);
for (int j = 0; j < 2; j++)
{
for (int i = 0; i < 4; i++)
{
// only put pixels out < width or height
if (((x + i) < width) && ((y + j) < height))
{
uint offset = (uint)(z * sizeofplane + (y + j) * bps + (x + i) * bpp + 3);
rawData[offset] = alphas[bits & 0x07];
}
bits >>= 3;
}
}
// Last three bytes
bits = *((uint *)&alphamask[3]);
for (int j = 2; j < 4; j++)
{
for (int i = 0; i < 4; i++)
{
// only put pixels out < width or height
if (((x + i) < width) && ((y + j) < height))
{
uint offset = (uint)(z * sizeofplane + (y + j) * bps + (x + i) * bpp + 3);
rawData[offset] = alphas[bits & 0x07];
}
bits >>= 3;
}
}
}
}
}
}
return(rawData);
}
