private static double GetCombinedEntropy(uint[] x, uint[] y, int length, bool isXUsed, bool isYUsed, bool trivialAtEnd, Vp8LStreaks stats, Vp8LBitEntropy bitEntropy)
{
stats.Clear();
bitEntropy.Init();
if (trivialAtEnd)
{
// This configuration is due to palettization that transforms an indexed
// pixel into 0xff000000 | (pixel << 8) in BundleColorMap.
// BitsEntropyRefine is 0 for histograms with only one non-zero value.
// Only FinalHuffmanCost needs to be evaluated.
// Deal with the non-zero value at index 0 or length-1.
stats.Streaks[1][0] = 1;
// Deal with the following/previous zero streak.
stats.Counts[0] = 1;
stats.Streaks[0][1] = length - 1;
return(stats.FinalHuffmanCost());
}
if (isXUsed)
{
if (isYUsed)
{
bitEntropy.GetCombinedEntropyUnrefined(x, y, length, stats);
}
else
{
bitEntropy.GetEntropyUnrefined(x, length, stats);
}
}
else
{
if (isYUsed)
{
bitEntropy.GetEntropyUnrefined(y, length, stats);
}
else
{
stats.Counts[0] = 1;
stats.Streaks[0][length > 3 ? 1 : 0] = length;
bitEntropy.Init();
}
}
return(bitEntropy.BitsEntropyRefine() + stats.FinalHuffmanCost());
}
/// <summary>
/// Get the symbol entropy for the distribution 'population'.
/// </summary>
private static double PopulationCost(uint[] population, int length, ref uint trivialSym, ref bool isUsed, Vp8LStreaks stats, Vp8LBitEntropy bitEntropy)
{
bitEntropy.Init();
stats.Clear();
bitEntropy.BitsEntropyUnrefined(population, length, stats);
trivialSym = (bitEntropy.NoneZeros == 1) ? bitEntropy.NoneZeroCode : NonTrivialSym;
// The histogram is used if there is at least one non-zero streak.
isUsed = stats.Streaks[1][0] != 0 || stats.Streaks[1][1] != 0;
return(bitEntropy.BitsEntropyRefine() + stats.FinalHuffmanCost());
}