internal static Bc2Block EncodeBlock(RawBlock4X4Rgba32 rawBlock)
{
var pixels = rawBlock.AsSpan;
PcaVectors.Create(pixels, out System.Numerics.Vector3 mean, out System.Numerics.Vector3 pa);
PcaVectors.GetMinMaxColor565(pixels, mean, pa, out var min, out var max);
var c0 = max;
var c1 = min;
Bc2Block best = TryColors(rawBlock, c0, c1, out float bestError);
for (int i = 0; i < maxTries; i++)
{
var(newC0, newC1) = ColorVariationGenerator.Variate565(c0, c1, i);
var block = TryColors(rawBlock, newC0, newC1, out var error);
if (error < bestError)
{
best = block;
bestError = error;
c0 = newC0;
c1 = newC1;
}
if (bestError < errorThreshold)
{
break;
}
}
return(best);
}
public void PrincipalAxisTest()
{
Vector4[] testData = new[] {
new Vector4(0.4f, 0.3f, 0.5f, 0.1f),
new Vector4(0.3f, 0.3f, 0.5f, 0.3f),
new Vector4(0.5f, 0.3f, 0.6f, 0.2f),
new Vector4(0.2f, 0.3f, 0.6f, 0.2f),
new Vector4(0.456f, 0.34f, 0.23f, 0.45f)
};
var refMean = new[] { 0.3712, 0.308, 0.48600000000000004, 0.25 };
var refCovar = new[] {
new[] { 0.014747200000000002, 0.00084800000000000088, -0.0067839999999999992, 0.0028000000000000004 },
new[] { 0.00084800000000000088, 0.00032000000000000062, -0.0025600000000000024, 0.0020000000000000018 },
new[] { -0.0067839999999999992, -0.0025600000000000024, 0.022979999999999993, -0.015999999999999997 },
new[] { 0.0028000000000000004, 0.0020000000000000018, -0.015999999999999997, 0.0174999 }
};
var covarianceMatrix = PcaVectors.CalculateCovariance(testData, out Vector4 mean);
var pa = PcaVectors.CalculatePrincipalAxis(covarianceMatrix);
var refPa = new double[4]
{
0.282, 0.087, -0.744, 0.603
};
Assert.Equal(refMean[0], mean.X, 2);
Assert.Equal(refMean[1], mean.Y, 2);
Assert.Equal(refMean[2], mean.Z, 2);
Assert.Equal(refMean[3], mean.W, 2);
Assert.Equal(refCovar[0][0], covarianceMatrix.M11, 4);
Assert.Equal(refCovar[0][1], covarianceMatrix.M12, 4);
Assert.Equal(refCovar[0][2], covarianceMatrix.M13, 4);
Assert.Equal(refCovar[0][3], covarianceMatrix.M14, 4);
Assert.Equal(refCovar[1][0], covarianceMatrix.M21, 4);
Assert.Equal(refCovar[1][1], covarianceMatrix.M22, 4);
Assert.Equal(refCovar[1][2], covarianceMatrix.M23, 4);
Assert.Equal(refCovar[1][3], covarianceMatrix.M24, 4);
Assert.Equal(refCovar[2][0], covarianceMatrix.M31, 4);
Assert.Equal(refCovar[2][1], covarianceMatrix.M32, 4);
Assert.Equal(refCovar[2][2], covarianceMatrix.M33, 4);
Assert.Equal(refCovar[2][3], covarianceMatrix.M34, 4);
Assert.Equal(refCovar[3][0], covarianceMatrix.M41, 4);
Assert.Equal(refCovar[3][1], covarianceMatrix.M42, 4);
Assert.Equal(refCovar[3][2], covarianceMatrix.M43, 4);
Assert.Equal(refCovar[3][3], covarianceMatrix.M44, 4);
Assert.True(Math.Abs(pa.X - refPa[0]) < 0.1f, $"actual: {pa.X} expected: {refPa[0]}");
Assert.True(Math.Abs(pa.Y - refPa[1]) < 0.1f, $"actual: {pa.Y} expected: {refPa[1]}");
Assert.True(Math.Abs(pa.Z - refPa[2]) < 0.1f, $"actual: {pa.Z} expected: {refPa[2]}");
Assert.True(Math.Abs(pa.W - refPa[3]) < 0.1f, $"actual: {pa.W} expected: {refPa[3]}");
}
internal static Bc3Block EncodeBlock(RawBlock4X4Rgba32 rawBlock)
{
var pixels = rawBlock.AsSpan;
PcaVectors.Create(pixels, out System.Numerics.Vector3 mean, out System.Numerics.Vector3 pa);
PcaVectors.GetMinMaxColor565(pixels, mean, pa, out var min, out var max);
var c0 = max;
var c1 = min;
if (c0.data < c1.data)
{
var c = c0;
c0 = c1;
c1 = c;
}
Bc3Block best = TryColors(rawBlock, c0, c1, out float bestError);
int lastChanged = 0;
for (int i = 0; i < maxTries; i++)
{
var(newC0, newC1) = ColorVariationGenerator.Variate565(c0, c1, i);
if (newC0.data < newC1.data)
{
var c = newC0;
newC0 = newC1;
newC1 = c;
}
var block = TryColors(rawBlock, newC0, newC1, out var error);
lastChanged++;
if (error < bestError)
{
best = block;
bestError = error;
c0 = newC0;
c1 = newC1;
lastChanged = 0;
}
if (bestError < errorThreshold || lastChanged > ColorVariationGenerator.VarPatternCount)
{
break;
}
}
best = FindAlphaValues(best, rawBlock, 8);
return(best);
}
internal static Bc2Block EncodeBlock(RawBlock4X4Rgba32 rawBlock)
{
var pixels = rawBlock.AsSpan;
PcaVectors.Create(pixels, out var mean, out var principalAxis);
PcaVectors.GetMinMaxColor565(pixels, mean, principalAxis, out var min, out var max);
ColorRgb565 c0 = max;
ColorRgb565 c1 = min;
var output = TryColors(rawBlock, c0, c1, out var _);
return(output);
}
internal static Bc3Block EncodeBlock(RawBlock4X4Rgba32 rawBlock)
{
var pixels = rawBlock.AsSpan;
PcaVectors.Create(pixels, out var mean, out var principalAxis);
PcaVectors.GetMinMaxColor565(pixels, mean, principalAxis, out var min, out var max);
ColorRgb565 c0 = max;
ColorRgb565 c1 = min;
if (c0.data <= c1.data)
{
var c = c0;
c0 = c1;
c1 = c;
}
var output = TryColors(rawBlock, c0, c1, out float _);
output = FindAlphaValues(output, rawBlock, 3);
return(output);
}