/// <summary>
/// Decode 4 bit RGBA texture from byte array
/// </summary>
/// <remarks>Assumes that input texture is square! (width == height)</remarks>
/// <param name="data">Byte array that contains encoded texture data</param>
/// <param name="width">Width of texture in pixels</param>
/// <returns>TempByteImageFormat</returns>
public static TempByteImageFormat DecodeRgba4Bpp(byte[] data, int width)
{
int size = width;
int blocks = size / 4;
int blockMask = blocks - 1;
TempByteImageFormat returnValue = new TempByteImageFormat(size, size, 4);
PvrtcPacket[] packets = new PvrtcPacket[blocks * blocks];
byte[] eightBytes = new byte[8];
for (int i = 0; i < packets.Length; i++)
{
packets[i] = new PvrtcPacket();
Buffer.BlockCopy(data, i * 8, eightBytes, 0, 8);
packets[i].InitFromBytes(eightBytes);
}
int currentFactorIndex = 0;
for (int y = 0; y < blocks; ++y)
{
for (int x = 0; x < blocks; ++x)
{
currentFactorIndex = 0;
PvrtcPacket packet = packets[MortonTable.GetMortonNumber(x, y)];
uint mod = packet.GetModulationData();
for (int py = 0; py < 4; ++py)
{
int yOffset = (py < 2) ? -1 : 0;
int y0 = (y + yOffset) & blockMask;
int y1 = (y0 + 1) & blockMask;
for (int px = 0; px < 4; ++px)
{
int xOffset = (px < 2) ? -1 : 0;
int x0 = (x + xOffset) & blockMask;
int x1 = (x0 + 1) & blockMask;
PvrtcPacket p0 = packets[MortonTable.GetMortonNumber(x0, y0)];
PvrtcPacket p1 = packets[MortonTable.GetMortonNumber(x1, y0)];
PvrtcPacket p2 = packets[MortonTable.GetMortonNumber(x0, y1)];
PvrtcPacket p3 = packets[MortonTable.GetMortonNumber(x1, y1)];
byte[] currentFactors = PvrtcPacket.BILINEAR_FACTORS[currentFactorIndex];
Vector4Int ca = p0.GetColorRgbaA() * currentFactors[0] +
p1.GetColorRgbaA() * currentFactors[1] +
p2.GetColorRgbaA() * currentFactors[2] +
p3.GetColorRgbaA() * currentFactors[3];
Vector4Int cb = p0.GetColorRgbaB() * currentFactors[0] +
p1.GetColorRgbaB() * currentFactors[1] +
p2.GetColorRgbaB() * currentFactors[2] +
p3.GetColorRgbaB() * currentFactors[3];
byte[] currentWeights = PvrtcPacket.WEIGHTS[4 * packet.GetPunchthroughAlpha() + mod & 3];
byte red = (byte)((ca.x * currentWeights[0] + cb.x * currentWeights[1]) >> 7);
byte green = (byte)((ca.y * currentWeights[0] + cb.y * currentWeights[1]) >> 7);
byte blue = (byte)((ca.z * currentWeights[0] + cb.z * currentWeights[1]) >> 7);
byte alpha = (byte)((ca.w * currentWeights[2] + cb.w * currentWeights[3]) >> 7);
returnValue.SetPixelChannels((px + x * 4), (py + y * 4), new byte[] { red, green, blue, alpha });
mod >>= 2;
currentFactorIndex++;
}
}
}
}
return(returnValue);
}
/// <summary>
/// Encodes RGBA texture into byte array
/// </summary>
/// <remarks>Texture must be square and power of two dimensions</remarks>
/// <param name="bitmap">TempByteImageFormat</param>
/// <returns>Byte array</returns>
public static byte[] EncodeRgba4Bpp(TempByteImageFormat bitmap)
{
if (bitmap.height != bitmap.width)
{
throw new ArgumentException("Texture isn't square!");
}
if (!((bitmap.height & (bitmap.height - 1)) == 0))
{
throw new ArgumentException("Texture resolution must be 2^N!");
}
int size = bitmap.width;
int blocks = size / 4;
int blockMask = blocks - 1;
PvrtcPacket[] packets = new PvrtcPacket[blocks * blocks];
for (int i = 0; i < packets.Length; i++)
{
packets[i] = new PvrtcPacket();
}
for (int y = 0; y < blocks; ++y)
{
for (int x = 0; x < blocks; ++x)
{
(byte[] minColor, byte[] maxColor) = GetMinMaxColorsWithAlpha(bitmap, 4 * x, 4 * y);
PvrtcPacket packet = packets[MortonTable.GetMortonNumber(x, y)];
packet.SetPunchthroughAlpha(false);
packet.SetColorA(minColor[0], minColor[1], minColor[2], minColor[3]);
packet.SetColorB(maxColor[0], maxColor[1], maxColor[2], maxColor[3]);
}
}
int currentFactorIndex = 0;
for (int y = 0; y < blocks; ++y)
{
for (int x = 0; x < blocks; ++x)
{
currentFactorIndex = 0;
uint modulationData = 0;
for (int py = 0; py < 4; ++py)
{
int yOffset = (py < 2) ? -1 : 0;
int y0 = (y + yOffset) & blockMask;
int y1 = (y0 + 1) & blockMask;
for (int px = 0; px < 4; ++px)
{
int xOffset = (px < 2) ? -1 : 0;
int x0 = (x + xOffset) & blockMask;
int x1 = (x0 + 1) & blockMask;
PvrtcPacket p0 = packets[MortonTable.GetMortonNumber(x0, y0)];
PvrtcPacket p1 = packets[MortonTable.GetMortonNumber(x1, y0)];
PvrtcPacket p2 = packets[MortonTable.GetMortonNumber(x0, y1)];
PvrtcPacket p3 = packets[MortonTable.GetMortonNumber(x1, y1)];
byte[] currentFactors = PvrtcPacket.BILINEAR_FACTORS[currentFactorIndex];
Vector4Int ca = p0.GetColorRgbaA() * currentFactors[0] +
p1.GetColorRgbaA() * currentFactors[1] +
p2.GetColorRgbaA() * currentFactors[2] +
p3.GetColorRgbaA() * currentFactors[3];
Vector4Int cb = p0.GetColorRgbaB() * currentFactors[0] +
p1.GetColorRgbaB() * currentFactors[1] +
p2.GetColorRgbaB() * currentFactors[2] +
p3.GetColorRgbaB() * currentFactors[3];
byte[] pixel = bitmap.GetPixelChannels(4 * x + px, 4 * y + py);
Vector4Int d = cb - ca;
Vector4Int p = new Vector4Int(pixel[0] * 16, pixel[1] * 16, pixel[2] * 16, pixel[3] * 16);
Vector4Int v = p - ca;
// PVRTC uses weightings of 0, 3/8, 5/8 and 1
// The boundaries for these are 3/16, 1/2 (=8/16), 13/16
int projection = (v % d) * 16; //Mathf.RoundToInt(Vector4.Dot(v, d)) * 16;
int lengthSquared = d % d; //Mathf.RoundToInt(Vector4.Dot(d,d));
if (projection > 3 * lengthSquared)
{
modulationData++;
}
if (projection > 8 * lengthSquared)
{
modulationData++;
}
if (projection > 13 * lengthSquared)
{
modulationData++;
}
modulationData = RotateRight(modulationData, 2);
currentFactorIndex++;
}
}
PvrtcPacket packet = packets[MortonTable.GetMortonNumber(x, y)];
packet.SetModulationData(modulationData);
}
}
byte[] returnValue = new byte[size * size / 2];
// Create final byte array from PVRTC packets
for (int i = 0; i < packets.Length; i++)
{
byte[] tempArray = packets[i].GetAsByteArray();
Buffer.BlockCopy(tempArray, 0, returnValue, 8 * i, 8);
}
return(returnValue);
}