public static byte[] EncodeRgb4Bpp(Bitmap bitmap)
{
if (bitmap.Height != bitmap.Width)
{
throw new Exception("Texture isn't square!");
}
if (!((bitmap.Height & (bitmap.Height - 1)) == 0))
{
throw new Exception("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)
{
Color minColor = Color.White; // white is same as all 255, should be same as Color.max
Color maxColor = Color.Black; // clear is same as all 0, should be same as Color.min
GetMinMaxColors(bitmap, 4 * x, 4 * y, ref minColor, ref maxColor);
PvrtcPacket packet = packets[GetMortonNumber(x, y)];
packet.SetPunchthroughAlpha(false);
packet.SetColorA(minColor.R, minColor.G, minColor.B);
packet.SetColorB(maxColor.R, maxColor.G, maxColor.B);
}
}
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[GetMortonNumber(x0, y0)];
PvrtcPacket p1 = packets[GetMortonNumber(x1, y0)];
PvrtcPacket p2 = packets[GetMortonNumber(x0, y1)];
PvrtcPacket p3 = packets[GetMortonNumber(x1, y1)];
byte[] currentFactors = PvrtcPacket.BILINEAR_FACTORS[currentFactorIndex];
Vector3Int ca = p0.GetColorRgbA() * currentFactors[0] +
p1.GetColorRgbA() * currentFactors[1] +
p2.GetColorRgbA() * currentFactors[2] +
p3.GetColorRgbA() * currentFactors[3];
Vector3Int cb = p0.GetColorRgbB() * currentFactors[0] +
p1.GetColorRgbB() * currentFactors[1] +
p2.GetColorRgbB() * currentFactors[2] +
p3.GetColorRgbB() * currentFactors[3];
Color pixel = bitmap.GetPixel(4 * x + px, 4 * y + py);
Vector3Int d = cb - ca;
Vector3Int p = new Vector3Int(pixel.R * 16, pixel.G * 16, pixel.B * 16);
Vector3Int 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(Vector3.Dot(v, d)) * 16;
int lengthSquared = d % d; //Mathf.RoundToInt(Vector3.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[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);
}
// This function assumes that input texture is square! (width == height)
public static Bitmap DecodeRgb4Bpp(byte[] data, int width)
{
int size = width;
int blocks = size / 4;
int blockMask = blocks - 1;
Bitmap returnValue = new Bitmap(size, size, PixelFormat.Format24bppRgb);
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[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[GetMortonNumber(x0, y0)];
PvrtcPacket p1 = packets[GetMortonNumber(x1, y0)];
PvrtcPacket p2 = packets[GetMortonNumber(x0, y1)];
PvrtcPacket p3 = packets[GetMortonNumber(x1, y1)];
byte[] currentFactors = PvrtcPacket.BILINEAR_FACTORS[currentFactorIndex];
Vector3Int ca = p0.GetColorRgbA() * currentFactors[0] +
p1.GetColorRgbA() * currentFactors[1] +
p2.GetColorRgbA() * currentFactors[2] +
p3.GetColorRgbA() * currentFactors[3];
Vector3Int cb = p0.GetColorRgbB() * currentFactors[0] +
p1.GetColorRgbB() * currentFactors[1] +
p2.GetColorRgbB() * currentFactors[2] +
p3.GetColorRgbB() * currentFactors[3];
byte[] currentWeights = PvrtcPacket.WEIGHTS[4 * packet.GetPunchthroughAlpha() + mod & 3];
Color c = Color.White;
c = Color.FromArgb(c.A,
(byte)((int)(Math.Round((decimal)(ca.x * currentWeights[0] + cb.x * currentWeights[1]), MidpointRounding.AwayFromZero)) >> 7),
(byte)((int)(Math.Round((decimal)(ca.y * currentWeights[0] + cb.y * currentWeights[1]), MidpointRounding.AwayFromZero)) >> 7),
(byte)((int)(Math.Round((decimal)(ca.z * currentWeights[0] + cb.z * currentWeights[1]), MidpointRounding.AwayFromZero)) >> 7));
returnValue.SetPixel((px + x * 4), (py + y * 4), c);
mod >>= 2;
currentFactorIndex++;
}
}
}
}
return(returnValue);
}