public static Bc7Block EncodeBlock(RawBlock4X4Rgba32 block, int startingVariation)
{
var type = Bc7BlockType.Type5;
Span <Bc7Block> outputs = stackalloc Bc7Block[4];
for (int rotation = 0; rotation < 4; rotation++)
{
var rotatedBlock = Bc7EncodingHelpers.RotateBlockColors(block, rotation);
Bc7Block output = new Bc7Block();
Bc7EncodingHelpers.GetInitialUnscaledEndpoints(rotatedBlock, out var ep0, out var ep1);
ColorRgba32 scaledEp0 =
Bc7EncodingHelpers.ScaleDownEndpoint(ep0, type, false, out byte _);
ColorRgba32 scaledEp1 =
Bc7EncodingHelpers.ScaleDownEndpoint(ep1, type, false, out byte _);
byte pBit = 0; //fake pBit
Bc7EncodingHelpers.OptimizeSubsetEndpointsWithPBit(type, rotatedBlock, ref scaledEp0,
ref scaledEp1, ref pBit, ref pBit, startingVariation, partitionTable, subset, false, true);
ep0 = Bc7EncodingHelpers.ExpandEndpoint(type, scaledEp0, 0);
ep1 = Bc7EncodingHelpers.ExpandEndpoint(type, scaledEp1, 0);
byte[] colorIndices = new byte[16];
byte[] alphaIndices = new byte[16];
Bc7EncodingHelpers.FillAlphaColorIndices(type, rotatedBlock,
ep0,
ep1,
colorIndices, alphaIndices);
bool needsRedo = false;
if ((colorIndices[0] & 0b10) > 0) //If anchor index most significant bit is 1, switch endpoints
{
var c = scaledEp0;
var alpha0 = scaledEp0.a;
var alpha1 = scaledEp1.a;
scaledEp0 = scaledEp1;
scaledEp1 = c;
scaledEp0.a = alpha0;
scaledEp1.a = alpha1;
needsRedo = true;
}
if ((alphaIndices[0] & 0b10) > 0) //If anchor index most significant bit is 1, switch endpoints
{
var a = scaledEp0.a;
scaledEp0.a = scaledEp1.a;
scaledEp1.a = a;
needsRedo = true;
}
if (needsRedo)
{
//redo indices
ep0 = Bc7EncodingHelpers.ExpandEndpoint(type, scaledEp0, 0);
ep1 = Bc7EncodingHelpers.ExpandEndpoint(type, scaledEp1, 0);
Bc7EncodingHelpers.FillAlphaColorIndices(type, rotatedBlock,
ep0,
ep1,
colorIndices, alphaIndices);
}
output.PackType5(rotation, new[] {
new byte[] { scaledEp0.r, scaledEp0.g, scaledEp0.b },
new byte[] { scaledEp1.r, scaledEp1.g, scaledEp1.b },
},
new[] { scaledEp0.a, scaledEp1.a },
colorIndices, alphaIndices);
outputs[rotation] = output;
}
int bestIndex = 0;
float bestError = 0;
bool first = true;
// Find best out of generated blocks
for (int i = 0; i < outputs.Length; i++)
{
var decoded = outputs[i].Decode();
float error = block.CalculateYCbCrAlphaError(decoded);
if (error < bestError || first)
{
first = false;
bestError = error;
bestIndex = i;
}
}
return(outputs[bestIndex]);
}
public static Bc7Block EncodeBlock(RawBlock4X4Rgba32 block, int startingVariation)
{
bool hasAlpha = block.HasTransparentPixels();
Bc7Block output = new Bc7Block();
Bc7EncodingHelpers.GetInitialUnscaledEndpoints(block, out var ep0, out var ep1);
ColorRgba32 scaledEp0 =
Bc7EncodingHelpers.ScaleDownEndpoint(ep0, Bc7BlockType.Type6, false, out byte pBit0);
ColorRgba32 scaledEp1 =
Bc7EncodingHelpers.ScaleDownEndpoint(ep1, Bc7BlockType.Type6, false, out byte pBit1);
ReadOnlySpan<int> partitionTable = new int[] { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
const int subset = 0;
//Force 255 alpha if fully opaque
if (!hasAlpha)
{
pBit0 = 1;
pBit1 = 1;
}
Bc7EncodingHelpers.OptimizeSubsetEndpointsWithPBit(Bc7BlockType.Type6, block, ref scaledEp0,
ref scaledEp1, ref pBit0, ref pBit1, startingVariation, partitionTable, subset, hasAlpha, hasAlpha);
ep0 = Bc7EncodingHelpers.ExpandEndpoint(Bc7BlockType.Type6, scaledEp0, pBit0);
ep1 = Bc7EncodingHelpers.ExpandEndpoint(Bc7BlockType.Type6, scaledEp1, pBit1);
byte[] indices = new byte[16];
Bc7EncodingHelpers.FillSubsetIndices(Bc7BlockType.Type6, block,
ep0,
ep1,
partitionTable, subset, indices);
if ((indices[0] & 0b1000) > 0) //If anchor index most significant bit is 1, switch endpoints
{
var c = scaledEp0;
var p = pBit0;
scaledEp0 = scaledEp1;
pBit0 = pBit1;
scaledEp1 = c;
pBit1 = p;
//redo indices
ep0 = Bc7EncodingHelpers.ExpandEndpoint(Bc7BlockType.Type6, scaledEp0, pBit0);
ep1 = Bc7EncodingHelpers.ExpandEndpoint(Bc7BlockType.Type6, scaledEp1, pBit1);
Bc7EncodingHelpers.FillSubsetIndices(Bc7BlockType.Type6, block,
ep0,
ep1,
partitionTable, subset, indices);
}
output.PackType6(new[]{
new byte[]{scaledEp0.r, scaledEp0.g, scaledEp0.b, scaledEp0.a},
new byte[]{scaledEp1.r, scaledEp1.g, scaledEp1.b, scaledEp1.a},
},
new[] { pBit0, pBit1 },
indices);
return output;
}
