Experimental RDO: Mode 6 with 2-bit index

LICENSE

@@ -1,6 +1,6 @@
 MIT License
 
-Copyright (c) 2019-2020 Andrew Evstyukhin
+Copyright (c) 2019-2021 Andrew Evstyukhin
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal

README.md

@@ -22,6 +22,10 @@ For premultiplied alpha it is necessary to specify "/nomask" command-line option
 
 Many encoders use single metric (RMSE / MSE / PSNR) insensitive to a direction. While SSIM is unhandy for direct compression, it enhances correlation when encoding produces equal deltas and so SSIM overcomes dithering.
 
+## Special features
+
+Additional mode 6 with 2-bit index instead of 4-bit gives a significant reduction in size.
+
 ## Usage
 
 The solution was tested on SSSE3, SSE4.1, AVX, AVX2, AVX-512BW - capable CPUs for Win64 API only.
@@ -63,7 +67,7 @@ Compressing "frymire.png" (gained from https://github.com/castano/nvidia-texture
           SubTexture RGB qMSE = 0.5, qPSNR = 50.950326, wSSIM_4x4 = 0.97143024
         Saved frymire.ktx
 
-Compressing "8192.png" (gained from https://bitbucket.org/wolfpld/etcpak/downloads/8192.png) in development mode:
+Compressing "8192.png" (gained from removed https://bitbucket.org/wolfpld/etcpak/downloads/8192.png) in development mode:
 
     Bc7Compress.exe /draft /nomask /noflip 8192.png 8192.ktx
     Loaded 8192.png
@@ -75,7 +79,7 @@ Compressing "8192.png" (gained from https://bitbucket.org/wolfpld/etcpak/downloa
 
 ## Copyright
 
-Copyright (c) 2019-2020 Andrew Evstyukhin
+Copyright (c) 2019-2021 Andrew Evstyukhin
 
 Licensed under the MIT License.
 

src/Bc7Compress.vcxproj

@@ -145,6 +145,7 @@
     <ClCompile Include="Bc7CoreMode4.cpp" />
     <ClCompile Include="Bc7CoreMode5.cpp" />
     <ClCompile Include="Bc7CoreMode6.cpp" />
+    <ClCompile Include="Bc7CoreMode6Index2.cpp" />
     <ClCompile Include="Bc7CoreMode7.cpp" />
     <ClCompile Include="Bc7PcaEigen.cpp" />
     <ClCompile Include="Bc7Tables.cpp" />

src/Bc7Compress.vcxproj.filters

@@ -115,5 +115,8 @@
     <ClCompile Include="Bc7PcaEigen.cpp">
       <Filter>Source Files</Filter>
     </ClCompile>
+    <ClCompile Include="Bc7CoreMode6Index2.cpp">
+      <Filter>Source Files</Filter>
+    </ClCompile>
   </ItemGroup>
 </Project>

src/Bc7Core.cpp

@@ -13,7 +13,7 @@
 #endif
 
 #if defined(OPTION_COUNTERS)
-static std::atomic_int gCounterModes[8];
+static std::atomic_int gCounterModes[9 + 1];
 static std::atomic_int gCompressAlready, gCompress, gCompressBad;
 #endif
 
@@ -1491,19 +1491,27 @@ static void CompressBlock(uint8_t output[16], Cell& input) noexcept
 
 			if (input.Error.Total > denoiseStep)
 			{
-				Mode6::CompressBlockFast(input);
+				if constexpr (kDenoise || kDenoiseStep)
+				{
+					Mode6Index2::CompressBlockFast(input);
+				}
 
 				if (input.Error.Total > denoiseStep)
 				{
-					Mode4::CompressBlockFast(input);
+					Mode6::CompressBlockFast(input);
 
 					if (input.Error.Total > denoiseStep)
 					{
-						Mode5::CompressBlockFast(input);
+						Mode4::CompressBlockFast(input);
 
 						if (input.Error.Total > denoiseStep)
 						{
-							Mode7::CompressBlockFast(input);
+							Mode5::CompressBlockFast(input);
+
+							if (input.Error.Total > denoiseStep)
+							{
+								Mode7::CompressBlockFast(input);
+							}
 						}
 					}
 				}
@@ -1596,6 +1604,13 @@ static void CompressBlock(uint8_t output[16], Cell& input) noexcept
 						Mode7::CompressBlock(input);
 					}
 					break;
+
+				case 9:
+					if (input.Error.Total > 0)
+					{
+						Mode6Index2::CompressBlock(input);
+					}
+					break;
 				}
 
 				input.PersonalParameter = input.BestParameter;
@@ -1708,6 +1723,10 @@ static void CompressBlock(uint8_t output[16], Cell& input) noexcept
 				case 7:
 					Mode7::FinalPackBlock(output, input);
 					break;
+
+				case 9:
+					Mode6Index2::FinalPackBlock(output, input);
+					break;
 				}
 
 				DecompressBlock(output, temp);
@@ -1751,8 +1770,8 @@ static void CompressBlock(uint8_t output[16], Cell& input) noexcept
 
 void CompressStatistics()
 {
-	PRINTF("[Transparent]\tM4 = %i, M6 = %i, M5 = %i, M7 = %i",
-		gCounterModes[4].load(), gCounterModes[6].load(), gCounterModes[5].load(), gCounterModes[7].load());
+	PRINTF("[Transparent]\tM4 = %i, M6I2 = %i, M6 = %i, M5 = %i, M7 = %i",
+		gCounterModes[4].load(), gCounterModes[9].load(), gCounterModes[6].load(), gCounterModes[5].load(), gCounterModes[7].load());
 
 	PRINTF("[Opaque]\tM1 = %i, M3 = %i, M2 = %i, M0 = %i",
 		gCounterModes[1].load(), gCounterModes[3].load(), gCounterModes[2].load(), gCounterModes[0].load());
@@ -1766,6 +1785,7 @@ void CompressStatistics()
 	Mode0::PrintCounters();
 
 	Mode4::PrintCounters();
+	Mode6Index2::PrintCounters();
 	Mode6::PrintCounters();
 	Mode5::PrintCounters();
 	Mode7::PrintCounters();

src/Bc7Core.h

@@ -241,6 +241,18 @@ namespace Mode5 {
 
 } // namespace Mode5
 
+namespace Mode6Index2 {
+
+	void FinalPackBlock(uint8_t output[16], Cell& input) noexcept;
+
+	void CompressBlockFast(Cell& input) noexcept;
+
+	void CompressBlock(Cell& input) noexcept;
+
+	void PrintCounters() noexcept;
+
+} // namespace Mode6Index2
+
 namespace Mode6 {
 
 	void DecompressBlock(uint8_t input[16], Cell& output) noexcept;
@@ -285,9 +297,7 @@ struct WorkerItem
 	uint8_t* _Cell;
 	uint8_t* _Mask;
 
-	WorkerItem()
-	{
-	}
+	WorkerItem() = default;
 
 	WorkerItem(uint8_t* output, uint8_t* cell, uint8_t* mask)
 		: _Output(output)