R/Ryujinx.Graphics.Texture/BCnDecoder.cs

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using Ryujinx.Common;
using System;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
namespace Ryujinx.Graphics.Texture
{
public static class BCnDecoder
{
private const int BlockWidth = 4;
private const int BlockHeight = 4;
public static byte[] DecodeBC4(ReadOnlySpan<byte> data, int width, int height, int depth, int levels, int layers, bool signed)
{
int size = 0;
for (int l = 0; l < levels; l++)
{
size += Math.Max(1, width >> l) * Math.Max(1, height >> l) * Math.Max(1, depth >> l) * layers;
}
byte[] output = new byte[size];
ReadOnlySpan<ulong> data64 = MemoryMarshal.Cast<byte, ulong>(data);
Span<byte> rPal = stackalloc byte[8];
int baseOOffs = 0;
for (int l = 0; l < levels; l++)
{
int w = BitUtils.DivRoundUp(width, BlockWidth);
int h = BitUtils.DivRoundUp(height, BlockHeight);
for (int l2 = 0; l2 < layers; l2++)
{
for (int z = 0; z < depth; z++)
{
for (int y = 0; y < h; y++)
{
int baseY = y * BlockHeight;
for (int x = 0; x < w; x++)
{
int baseX = x * BlockWidth;
int lineBaseOOffs = baseOOffs + baseX;
ulong block = data64[0];
rPal[0] = (byte)block;
rPal[1] = (byte)(block >> 8);
if (signed)
{
CalculateBC3AlphaS(rPal);
}
else
{
CalculateBC3Alpha(rPal);
}
ulong rI = block >> 16;
for (int texel = 0; texel < BlockWidth * BlockHeight; texel++)
{
int tX = texel & 3;
int tY = texel >> 2;
if (baseX + tX >= width || baseY + tY >= height)
{
continue;
}
int shift = texel * 3;
byte r = rPal[(int)((rI >> shift) & 7)];
int oOffs = lineBaseOOffs + tY * width + tX;
output[oOffs] = r;
}
data64 = data64.Slice(1);
}
baseOOffs += width * (baseY + BlockHeight > height ? (height & (BlockHeight - 1)) : BlockHeight);
}
}
}
width = Math.Max(1, width >> 1);
height = Math.Max(1, height >> 1);
depth = Math.Max(1, depth >> 1);
}
return output;
}
public static byte[] DecodeBC5(ReadOnlySpan<byte> data, int width, int height, int depth, int levels, int layers, bool signed)
{
int size = 0;
for (int l = 0; l < levels; l++)
{
size += Math.Max(1, width >> l) * Math.Max(1, height >> l) * Math.Max(1, depth >> l) * layers * 2;
}
byte[] output = new byte[size];
ReadOnlySpan<ulong> data64 = MemoryMarshal.Cast<byte, ulong>(data);
Span<byte> rPal = stackalloc byte[8];
Span<byte> gPal = stackalloc byte[8];
int baseOOffs = 0;
for (int l = 0; l < levels; l++)
{
int w = BitUtils.DivRoundUp(width, BlockWidth);
int h = BitUtils.DivRoundUp(height, BlockHeight);
for (int l2 = 0; l2 < layers; l2++)
{
for (int z = 0; z < depth; z++)
{
for (int y = 0; y < h; y++)
{
int baseY = y * BlockHeight;
for (int x = 0; x < w; x++)
{
int baseX = x * BlockWidth;
int lineBaseOOffs = baseOOffs + baseX;
ulong blockL = data64[0];
ulong blockH = data64[1];
rPal[0] = (byte)blockL;
rPal[1] = (byte)(blockL >> 8);
gPal[0] = (byte)blockH;
gPal[1] = (byte)(blockH >> 8);
if (signed)
{
CalculateBC3AlphaS(rPal);
CalculateBC3AlphaS(gPal);
}
else
{
CalculateBC3Alpha(rPal);
CalculateBC3Alpha(gPal);
}
ulong rI = blockL >> 16;
ulong gI = blockH >> 16;
for (int texel = 0; texel < BlockWidth * BlockHeight; texel++)
{
int tX = texel & 3;
int tY = texel >> 2;
if (baseX + tX >= width || baseY + tY >= height)
{
continue;
}
int shift = texel * 3;
byte r = rPal[(int)((rI >> shift) & 7)];
byte g = gPal[(int)((gI >> shift) & 7)];
int oOffs = (lineBaseOOffs + tY * width + tX) * 2;
output[oOffs + 0] = r;
output[oOffs + 1] = g;
}
data64 = data64.Slice(2);
}
baseOOffs += width * (baseY + BlockHeight > height ? (height & (BlockHeight - 1)) : BlockHeight);
}
}
}
width = Math.Max(1, width >> 1);
height = Math.Max(1, height >> 1);
depth = Math.Max(1, depth >> 1);
}
return output;
}
[MethodImpl(MethodImplOptions.AggressiveInlining)]
private static void CalculateBC3Alpha(Span<byte> alpha)
{
for (int i = 2; i < 8; i++)
{
if (alpha[0] > alpha[1])
{
alpha[i] = (byte)(((8 - i) * alpha[0] + (i - 1) * alpha[1]) / 7);
}
else if (i < 6)
{
alpha[i] = (byte)(((6 - i) * alpha[0] + (i - 1) * alpha[1]) / 7);
}
else if (i == 6)
{
alpha[i] = 0;
}
else /* i == 7 */
{
alpha[i] = 0xff;
}
}
}
[MethodImpl(MethodImplOptions.AggressiveInlining)]
private static void CalculateBC3AlphaS(Span<byte> alpha)
{
for (int i = 2; i < 8; i++)
{
if ((sbyte)alpha[0] > (sbyte)alpha[1])
{
alpha[i] = (byte)(((8 - i) * (sbyte)alpha[0] + (i - 1) * (sbyte)alpha[1]) / 7);
}
else if (i < 6)
{
alpha[i] = (byte)(((6 - i) * (sbyte)alpha[0] + (i - 1) * (sbyte)alpha[1]) / 7);
}
else if (i == 6)
{
alpha[i] = 0x80;
}
else /* i == 7 */
{
alpha[i] = 0x7f;
}
}
}
}
}