1 files changed, 220 insertions, 0 deletions
diff --git a/Ryujinx.Graphics.Texture/BC7Decoder.cs b/Ryujinx.Graphics.Texture/BC7Decoder.cs
new file mode 100644
index 00000000..060d1ab8
--- /dev/null
+++ b/Ryujinx.Graphics.Texture/BC7Decoder.cs
@@ -0,0 +1,220 @@
+using Ryujinx.Graphics.Texture.Utils;
+using System.Diagnostics;
+using System;
+using System.Numerics;
+using System.Runtime.InteropServices;
+
+namespace Ryujinx.Graphics.Texture
+{
+    static class BC7Decoder
+    {
+        public static void Decode(Span<byte> output, ReadOnlySpan<byte> data, int width, int height)
+        {
+            ReadOnlySpan<Block> blocks = MemoryMarshal.Cast<byte, Block>(data);
+
+            Span<uint> output32 = MemoryMarshal.Cast<byte, uint>(output);
+
+            int wInBlocks = (width + 3) / 4;
+            int hInBlocks = (height + 3) / 4;
+
+            for (int y = 0; y < hInBlocks; y++)
+            {
+                int y2 = y * 4;
+                int bh = Math.Min(4, height - y2);
+
+                for (int x = 0; x < wInBlocks; x++)
+                {
+                    int x2 = x * 4;
+                    int bw = Math.Min(4, width - x2);
+
+                    DecodeBlock(blocks[y * wInBlocks + x], output32.Slice(y2 * width + x2), bw, bh, width);
+                }
+            }
+        }
+
+        private static void DecodeBlock(Block block, Span<uint> output, int w, int h, int width)
+        {
+            int mode = BitOperations.TrailingZeroCount((byte)block.Low | 0x100);
+            if (mode == 8)
+            {
+                // Mode is invalid, the spec mandates that hardware fills the block with
+                // a transparent black color.
+                for (int ty = 0; ty < h; ty++)
+                {
+                    int baseOffs = ty * width;
+
+                    for (int tx = 0; tx < w; tx++)
+                    {
+                        int offs = baseOffs + tx;
+
+                        output[offs] = 0;
+                    }
+                }
+
+                return;
+            }
+
+            BC7ModeInfo modeInfo = BC67Tables.BC7ModeInfos[mode];
+
+            int offset = mode + 1;
+            int partition = (int)block.Decode(ref offset, modeInfo.PartitionBitCount);
+            int rotation = (int)block.Decode(ref offset, modeInfo.RotationBitCount);
+            int indexMode = (int)block.Decode(ref offset, modeInfo.IndexModeBitCount);
+
+            Debug.Assert(partition < 64);
+            Debug.Assert(rotation < 4);
+            Debug.Assert(indexMode < 2);
+
+            int endPointCount = modeInfo.SubsetCount * 2;
+
+            Span<RgbaColor32> endPoints = stackalloc RgbaColor32[endPointCount];
+            Span<byte> pValues = stackalloc byte[modeInfo.PBits];
+
+            endPoints.Fill(new RgbaColor32(0, 0, 0, 255));
+
+            for (int i = 0; i < endPointCount; i++)
+            {
+                endPoints[i].R = (int)block.Decode(ref offset, modeInfo.ColorDepth);
+            }
+
+            for (int i = 0; i < endPointCount; i++)
+            {
+                endPoints[i].G = (int)block.Decode(ref offset, modeInfo.ColorDepth);
+            }
+
+            for (int i = 0; i < endPointCount; i++)
+            {
+                endPoints[i].B = (int)block.Decode(ref offset, modeInfo.ColorDepth);
+            }
+
+            if (modeInfo.AlphaDepth != 0)
+            {
+                for (int i = 0; i < endPointCount; i++)
+                {
+                    endPoints[i].A = (int)block.Decode(ref offset, modeInfo.AlphaDepth);
+                }
+            }
+
+            for (int i = 0; i < modeInfo.PBits; i++)
+            {
+                pValues[i] = (byte)block.Decode(ref offset, 1);
+            }
+
+            for (int i = 0; i < endPointCount; i++)
+            {
+                int pBit = -1;
+
+                if (modeInfo.PBits != 0)
+                {
+                    int pIndex = (i * modeInfo.PBits) / endPointCount;
+                    pBit = pValues[pIndex];
+                }
+
+                Unquantize(ref endPoints[i], modeInfo.ColorDepth, modeInfo.AlphaDepth, pBit);
+            }
+
+            byte[] partitionTable = BC67Tables.PartitionTable[modeInfo.SubsetCount - 1][partition];
+            byte[] fixUpTable = BC67Tables.FixUpIndices[modeInfo.SubsetCount - 1][partition];
+
+            Span<byte> colorIndices = stackalloc byte[16];
+
+            for (int i = 0; i < 16; i++)
+            {
+                byte subset = partitionTable[i];
+                int bitCount = i == fixUpTable[subset] ? modeInfo.ColorIndexBitCount - 1 : modeInfo.ColorIndexBitCount;
+
+                colorIndices[i] = (byte)block.Decode(ref offset, bitCount);
+                Debug.Assert(colorIndices[i] < 16);
+            }
+
+            Span<byte> alphaIndices = stackalloc byte[16];
+
+            if (modeInfo.AlphaIndexBitCount != 0)
+            {
+                for (int i = 0; i < 16; i++)
+                {
+                    int bitCount = i != 0 ? modeInfo.AlphaIndexBitCount : modeInfo.AlphaIndexBitCount - 1;
+
+                    alphaIndices[i] = (byte)block.Decode(ref offset, bitCount);
+                    Debug.Assert(alphaIndices[i] < 16);
+                }
+            }
+
+            for (int ty = 0; ty < h; ty++)
+            {
+                int baseOffs = ty * width;
+
+                for (int tx = 0; tx < w; tx++)
+                {
+                    int i = ty * 4 + tx;
+
+                    RgbaColor32 color;
+
+                    byte subset = partitionTable[i];
+
+                    RgbaColor32 color1 = endPoints[subset * 2];
+                    RgbaColor32 color2 = endPoints[subset * 2 + 1];
+
+                    if (modeInfo.AlphaIndexBitCount != 0)
+                    {
+                        if (indexMode == 0)
+                        {
+                            color = BC67Utils.Interpolate(color1, color2, colorIndices[i], alphaIndices[i], modeInfo.ColorIndexBitCount, modeInfo.AlphaIndexBitCount);
+                        }
+                        else
+                        {
+                            color = BC67Utils.Interpolate(color1, color2, alphaIndices[i], colorIndices[i], modeInfo.AlphaIndexBitCount, modeInfo.ColorIndexBitCount);
+                        }
+                    }
+                    else
+                    {
+                        color = BC67Utils.Interpolate(color1, color2, colorIndices[i], colorIndices[i], modeInfo.ColorIndexBitCount, modeInfo.ColorIndexBitCount);
+                    }
+
+                    if (rotation != 0)
+                    {
+                        int a = color.A;
+
+                        switch (rotation)
+                        {
+                            case 1: color.A = color.R; color.R = a; break;
+                            case 2: color.A = color.G; color.G = a; break;
+                            case 3: color.A = color.B; color.B = a; break;
+                        }
+                    }
+
+                    RgbaColor8 color8 = color.GetColor8();
+
+                    output[baseOffs + tx] = color8.ToUInt32();
+                }
+            }
+        }
+
+        private static void Unquantize(ref RgbaColor32 color, int colorDepth, int alphaDepth, int pBit)
+        {
+            color.R = UnquantizeComponent(color.R, colorDepth, pBit);
+            color.G = UnquantizeComponent(color.G, colorDepth, pBit);
+            color.B = UnquantizeComponent(color.B, colorDepth, pBit);
+            color.A = alphaDepth != 0 ? UnquantizeComponent(color.A, alphaDepth, pBit) : 255;
+        }
+
+        private static int UnquantizeComponent(int component, int bits, int pBit)
+        {
+            int shift = 8 - bits;
+            int value = component << shift;
+
+            if (pBit >= 0)
+            {
+                Debug.Assert(pBit <= 1);
+                value |= value >> (bits + 1);
+                value |= pBit << (shift - 1);
+            }
+            else
+            {
+                value |= value >> bits;
+            }
+
+            return value;
+        }
+    }
+}