src/Renderer/ETC_Decoder.cpp

// Copyright 2016 The SwiftShader Authors. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//    http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#include "ETC_Decoder.hpp"

namespace
{
	inline int clampByte(int value)
	{
		return (value < 0) ? 0 : ((value > 255) ? 255 : value);
	}

	inline int clampSByte(int value)
	{
		return (value < -128) ? -128 : ((value > 127) ? 127 : value);
	}

	inline int clampEAC(int value, bool isSigned)
	{
		int min = isSigned ? -1023 : 0;
		int max = isSigned ? 1023 : 2047;
		return (value < min) ? min : ((value > max) ? max : value);
	}

	struct bgra8
	{
		unsigned char b;
		unsigned char g;
		unsigned char r;
		unsigned char a;

		inline bgra8()
		{
		}

		inline void set(int red, int green, int blue)
		{
			r = static_cast<unsigned char>(clampByte(red));
			g = static_cast<unsigned char>(clampByte(green));
			b = static_cast<unsigned char>(clampByte(blue));
		}

		inline void set(int red, int green, int blue, int alpha)
		{
			r = static_cast<unsigned char>(clampByte(red));
			g = static_cast<unsigned char>(clampByte(green));
			b = static_cast<unsigned char>(clampByte(blue));
			a = static_cast<unsigned char>(clampByte(alpha));
		}

		const bgra8& addA(int alpha)
		{
			a = alpha;
			return *this;
		}
	};

	inline int extend_4to8bits(int x)
	{
		return (x << 4) | x;
	}

	inline int extend_5to8bits(int x)
	{
		return (x << 3) | (x >> 2);
	}

	inline int extend_6to8bits(int x)
	{
		return (x << 2) | (x >> 4);
	}

	inline int extend_7to8bits(int x)
	{
		return (x << 1) | (x >> 6);
	}

	struct ETC2
	{
		// Decodes unsigned single or dual channel block to bytes
		static void DecodeBlock(const ETC2** sources, unsigned char *dest, int nbChannels, int x, int y, int w, int h, int pitch, bool isSigned, bool isEAC)
		{
			if(isEAC)
			{
				for(int j = 0; j < 4 && (y + j) < h; j++)
				{
					int* sDst = reinterpret_cast<int*>(dest);
					for(int i = 0; i < 4 && (x + i) < w; i++)
					{
						for(int c = nbChannels - 1; c >= 0; c--)
						{
							sDst[i * nbChannels + c] = clampEAC(sources[c]->getSingleChannel(i, j, isSigned, true), isSigned);
						}
					}
					dest += pitch;
				}
			}
			else
			{
				if(isSigned)
				{
					signed char* sDst = reinterpret_cast<signed char*>(dest);
					for(int j = 0; j < 4 && (y + j) < h; j++)
					{
						for(int i = 0; i < 4 && (x + i) < w; i++)
						{
							for(int c = nbChannels - 1; c >= 0; c--)
							{
								sDst[i * nbChannels + c] = clampSByte(sources[c]->getSingleChannel(i, j, isSigned, false));
							}
						}
						sDst += pitch;
					}
				}
				else
				{
					for(int j = 0; j < 4 && (y + j) < h; j++)
					{
						for(int i = 0; i < 4 && (x + i) < w; i++)
						{
							for(int c = nbChannels - 1; c >= 0; c--)
							{
								dest[i * nbChannels + c] = clampByte(sources[c]->getSingleChannel(i, j, isSigned, false));
							}
						}
						dest += pitch;
					}
				}
			}
		}

		// Decodes RGB block to bgra8
		void decodeBlock(unsigned char *dest, int x, int y, int w, int h, int pitch, unsigned char alphaValues[4][4], bool punchThroughAlpha) const
		{
			bool opaqueBit = diffbit;
			bool nonOpaquePunchThroughAlpha = punchThroughAlpha && !opaqueBit;

			// Select mode
			if(diffbit || punchThroughAlpha)
			{
				int r = (R + dR);
				int g = (G + dG);
				int b = (B + dB);
				if(r < 0 || r > 31)
				{
					decodeTBlock(dest, x, y, w, h, pitch, alphaValues, nonOpaquePunchThroughAlpha);
				}
				else if(g < 0 || g > 31)
				{
					decodeHBlock(dest, x, y, w, h, pitch, alphaValues, nonOpaquePunchThroughAlpha);
				}
				else if(b < 0 || b > 31)
				{
					decodePlanarBlock(dest, x, y, w, h, pitch, alphaValues);
				}
				else
				{
					decodeDifferentialBlock(dest, x, y, w, h, pitch, alphaValues, nonOpaquePunchThroughAlpha);
				}
			}
			else
			{
				decodeIndividualBlock(dest, x, y, w, h, pitch, alphaValues, nonOpaquePunchThroughAlpha);
			}
		}

	private:
		struct
		{
			union
			{
				// Individual, differential, H and T modes
				struct
				{
					union
					{
						// Individual and differential modes
						struct
						{
							union
							{
								struct   // Individual colors
								{
									unsigned char R2 : 4;
									unsigned char R1 : 4;
									unsigned char G2 : 4;
									unsigned char G1 : 4;
									unsigned char B2 : 4;
									unsigned char B1 : 4;
								};

								struct   // Differential colors
								{
									signed char dR : 3;
									unsigned char R : 5;
									signed char dG : 3;
									unsigned char G : 5;
									signed char dB : 3;
									unsigned char B : 5;
								};
							};

							bool flipbit : 1;
							bool diffbit : 1;
							unsigned char cw2 : 3;
							unsigned char cw1 : 3;
						};

						// T mode
						struct
						{
							// Byte 1
							unsigned char TR1b : 2;
							unsigned char TdummyB : 1;
							unsigned char TR1a : 2;
							unsigned char TdummyA : 3;

							// Byte 2
							unsigned char TB1 : 4;
							unsigned char TG1 : 4;

							// Byte 3
							unsigned char TG2 : 4;
							unsigned char TR2 : 4;

							// Byte 4
							unsigned char Tdb : 1;
							bool Tflipbit : 1;
							unsigned char Tda : 2;
							unsigned char TB2 : 4;
						};

						// H mode
						struct
						{
							// Byte 1
							unsigned char HG1a : 3;
							unsigned char HR1 : 4;
							unsigned char HdummyA : 1;

							// Byte 2
							unsigned char HB1b : 2;
							unsigned char HdummyC : 1;
							unsigned char HB1a : 1;
							unsigned char HG1b : 1;
							unsigned char HdummyB : 3;

							// Byte 3
							unsigned char HG2a : 3;
							unsigned char HR2 : 4;
							unsigned char HB1c : 1;

							// Byte 4
							unsigned char Hdb : 1;
							bool Hflipbit : 1;
							unsigned char Hda : 1;
							unsigned char HB2 : 4;
							unsigned char HG2b : 1;
						};
					};

					unsigned char pixelIndexMSB[2];
					unsigned char pixelIndexLSB[2];
				};

				// planar mode
				struct
				{
					// Byte 1
					unsigned char GO1 : 1;
					unsigned char RO : 6;
					unsigned char PdummyA : 1;

					// Byte 2
					unsigned char BO1 : 1;
					unsigned char GO2 : 6;
					unsigned char PdummyB : 1;

					// Byte 3
					unsigned char BO3a : 2;
					unsigned char PdummyD : 1;
					unsigned char BO2 : 2;
					unsigned char PdummyC : 3;

					// Byte 4
					unsigned char RH2 : 1;
					bool Pflipbit : 1;
					unsigned char RH1 : 5;
					unsigned char BO3b : 1;

					// Byte 5
					unsigned char BHa : 1;
					unsigned char GH : 7;

					// Byte 6
					unsigned char RVa : 3;
					unsigned char BHb : 5;

					// Byte 7
					unsigned char GVa : 5;
					unsigned char RVb : 3;

					// Byte 8
					unsigned char BV : 6;
					unsigned char GVb : 2;
				};

				// Single channel block
				struct
				{
					union
					{
						unsigned char base_codeword;
						signed char signed_base_codeword;
					};

					unsigned char table_index : 4;
					unsigned char multiplier : 4;

					unsigned char mc1 : 2;
					unsigned char mb : 3;
					unsigned char ma : 3;

					unsigned char mf1 : 1;
					unsigned char me : 3;
					unsigned char md : 3;
					unsigned char mc2 : 1;

					unsigned char mh : 3;
					unsigned char mg : 3;
					unsigned char mf2 : 2;

					unsigned char mk1 : 2;
					unsigned char mj : 3;
					unsigned char mi : 3;

					unsigned char mn1 : 1;
					unsigned char mm : 3;
					unsigned char ml : 3;
					unsigned char mk2 : 1;

					unsigned char mp : 3;
					unsigned char mo : 3;
					unsigned char mn2 : 2;
				};
			};
		};

		void decodeIndividualBlock(unsigned char *dest, int x, int y, int w, int h, int pitch, unsigned char alphaValues[4][4], bool nonOpaquePunchThroughAlpha) const
		{
			int r1 = extend_4to8bits(R1);
			int g1 = extend_4to8bits(G1);
			int b1 = extend_4to8bits(B1);

			int r2 = extend_4to8bits(R2);
			int g2 = extend_4to8bits(G2);
			int b2 = extend_4to8bits(B2);

			decodeIndividualOrDifferentialBlock(dest, x, y, w, h, pitch, r1, g1, b1, r2, g2, b2, alphaValues, nonOpaquePunchThroughAlpha);
		}

		void decodeDifferentialBlock(unsigned char *dest, int x, int y, int w, int h, int pitch, unsigned char alphaValues[4][4], bool nonOpaquePunchThroughAlpha) const
		{
			int b1 = extend_5to8bits(B);
			int g1 = extend_5to8bits(G);
			int r1 = extend_5to8bits(R);

			int r2 = extend_5to8bits(R + dR);
			int g2 = extend_5to8bits(G + dG);
			int b2 = extend_5to8bits(B + dB);

			decodeIndividualOrDifferentialBlock(dest, x, y, w, h, pitch, r1, g1, b1, r2, g2, b2, alphaValues, nonOpaquePunchThroughAlpha);
		}

		void decodeIndividualOrDifferentialBlock(unsigned char *dest, int x, int y, int w, int h, int pitch, int r1, int g1, int b1, int r2, int g2, int b2, unsigned char alphaValues[4][4], bool nonOpaquePunchThroughAlpha) const
		{
			// Table 3.17.2 sorted according to table 3.17.3
			static const int intensityModifierDefault[8][4] =
			{
				{ 2, 8, -2, -8 },
				{ 5, 17, -5, -17 },
				{ 9, 29, -9, -29 },
				{ 13, 42, -13, -42 },
				{ 18, 60, -18, -60 },
				{ 24, 80, -24, -80 },
				{ 33, 106, -33, -106 },
				{ 47, 183, -47, -183 }
			};

			// Table C.12, intensity modifier for non opaque punchthrough alpha
			static const int intensityModifierNonOpaque[8][4] =
			{
				{ 0, 8, 0, -8 },
				{ 0, 17, 0, -17 },
				{ 0, 29, 0, -29 },
				{ 0, 42, 0, -42 },
				{ 0, 60, 0, -60 },
				{ 0, 80, 0, -80 },
				{ 0, 106, 0, -106 },
				{ 0, 183, 0, -183 }
			};

			const int(&intensityModifier)[8][4] = nonOpaquePunchThroughAlpha ? intensityModifierNonOpaque : intensityModifierDefault;

			bgra8 subblockColors0[4];
			bgra8 subblockColors1[4];

			const int i10 = intensityModifier[cw1][0];
			const int i11 = intensityModifier[cw1][1];
			const int i12 = intensityModifier[cw1][2];
			const int i13 = intensityModifier[cw1][3];

			subblockColors0[0].set(r1 + i10, g1 + i10, b1 + i10);
			subblockColors0[1].set(r1 + i11, g1 + i11, b1 + i11);
			subblockColors0[2].set(r1 + i12, g1 + i12, b1 + i12);
			subblockColors0[3].set(r1 + i13, g1 + i13, b1 + i13);

			const int i20 = intensityModifier[cw2][0];
			const int i21 = intensityModifier[cw2][1];
			const int i22 = intensityModifier[cw2][2];
			const int i23 = intensityModifier[cw2][3];

			subblockColors1[0].set(r2 + i20, g2 + i20, b2 + i20);
			subblockColors1[1].set(r2 + i21, g2 + i21, b2 + i21);
			subblockColors1[2].set(r2 + i22, g2 + i22, b2 + i22);
			subblockColors1[3].set(r2 + i23, g2 + i23, b2 + i23);

			unsigned char* destStart = dest;

			if(flipbit)
			{
				for(int j = 0; j < 2 && (y + j) < h; j++)
				{
					bgra8* color = (bgra8*)dest;
					if((x + 0) < w) color[0] = subblockColors0[getIndex(0, j)].addA(alphaValues[j][0]);
					if((x + 1) < w) color[1] = subblockColors0[getIndex(1, j)].addA(alphaValues[j][1]);
					if((x + 2) < w) color[2] = subblockColors0[getIndex(2, j)].addA(alphaValues[j][2]);
					if((x + 3) < w) color[3] = subblockColors0[getIndex(3, j)].addA(alphaValues[j][3]);
					dest += pitch;
				}

				for(int j = 2; j < 4 && (y + j) < h; j++)
				{
					bgra8* color = (bgra8*)dest;
					if((x + 0) < w) color[0] = subblockColors1[getIndex(0, j)].addA(alphaValues[j][0]);
					if((x + 1) < w) color[1] = subblockColors1[getIndex(1, j)].addA(alphaValues[j][1]);
					if((x + 2) < w) color[2] = subblockColors1[getIndex(2, j)].addA(alphaValues[j][2]);
					if((x + 3) < w) color[3] = subblockColors1[getIndex(3, j)].addA(alphaValues[j][3]);
					dest += pitch;
				}
			}
			else
			{
				for(int j = 0; j < 4 && (y + j) < h; j++)
				{
					bgra8* color = (bgra8*)dest;
					if((x + 0) < w) color[0] = subblockColors0[getIndex(0, j)].addA(alphaValues[j][0]);
					if((x + 1) < w) color[1] = subblockColors0[getIndex(1, j)].addA(alphaValues[j][1]);
					if((x + 2) < w) color[2] = subblockColors1[getIndex(2, j)].addA(alphaValues[j][2]);
					if((x + 3) < w) color[3] = subblockColors1[getIndex(3, j)].addA(alphaValues[j][3]);
					dest += pitch;
				}
			}

			if(nonOpaquePunchThroughAlpha)
			{
				decodePunchThroughAlphaBlock(destStart, x, y, w, h, pitch);
			}
		}

		void decodeTBlock(unsigned char *dest, int x, int y, int w, int h, int pitch, unsigned char alphaValues[4][4], bool nonOpaquePunchThroughAlpha) const
		{
			// Table C.8, distance index fot T and H modes
			static const int distance[8] = { 3, 6, 11, 16, 23, 32, 41, 64 };

			bgra8 paintColors[4];

			int r1 = extend_4to8bits(TR1a << 2 | TR1b);
			int g1 = extend_4to8bits(TG1);
			int b1 = extend_4to8bits(TB1);

			int r2 = extend_4to8bits(TR2);
			int g2 = extend_4to8bits(TG2);
			int b2 = extend_4to8bits(TB2);

			const int d = distance[Tda << 1 | Tdb];

			paintColors[0].set(r1, g1, b1);
			paintColors[1].set(r2 + d, g2 + d, b2 + d);
			paintColors[2].set(r2, g2, b2);
			paintColors[3].set(r2 - d, g2 - d, b2 - d);

			unsigned char* destStart = dest;

			for(int j = 0; j < 4 && (y + j) < h; j++)
			{
				bgra8* color = (bgra8*)dest;
				if((x + 0) < w) color[0] = paintColors[getIndex(0, j)].addA(alphaValues[j][0]);
				if((x + 1) < w) color[1] = paintColors[getIndex(1, j)].addA(alphaValues[j][1]);
				if((x + 2) < w) color[2] = paintColors[getIndex(2, j)].addA(alphaValues[j][2]);
				if((x + 3) < w) color[3] = paintColors[getIndex(3, j)].addA(alphaValues[j][3]);
				dest += pitch;
			}

			if(nonOpaquePunchThroughAlpha)
			{
				decodePunchThroughAlphaBlock(destStart, x, y, w, h, pitch);
			}
		}

		void decodeHBlock(unsigned char *dest, int x, int y, int w, int h, int pitch, unsigned char alphaValues[4][4], bool nonOpaquePunchThroughAlpha) const
		{
			// Table C.8, distance index fot T and H modes
			static const int distance[8] = { 3, 6, 11, 16, 23, 32, 41, 64 };

			bgra8 paintColors[4];

			int r1 = extend_4to8bits(HR1);
			int g1 = extend_4to8bits(HG1a << 1 | HG1b);
			int b1 = extend_4to8bits(HB1a << 3 | HB1b << 1 | HB1c);

			int r2 = extend_4to8bits(HR2);
			int g2 = extend_4to8bits(HG2a << 1 | HG2b);
			int b2 = extend_4to8bits(HB2);

			const int d = distance[(Hda << 2) | (Hdb << 1) | ((r1 << 16 | g1 << 8 | b1) >= (r2 << 16 | g2 << 8 | b2) ? 1 : 0)];

			paintColors[0].set(r1 + d, g1 + d, b1 + d);
			paintColors[1].set(r1 - d, g1 - d, b1 - d);
			paintColors[2].set(r2 + d, g2 + d, b2 + d);
			paintColors[3].set(r2 - d, g2 - d, b2 - d);

			unsigned char* destStart = dest;

			for(int j = 0; j < 4 && (y + j) < h; j++)
			{
				bgra8* color = (bgra8*)dest;
				if((x + 0) < w) color[0] = paintColors[getIndex(0, j)].addA(alphaValues[j][0]);
				if((x + 1) < w) color[1] = paintColors[getIndex(1, j)].addA(alphaValues[j][1]);
				if((x + 2) < w) color[2] = paintColors[getIndex(2, j)].addA(alphaValues[j][2]);
				if((x + 3) < w) color[3] = paintColors[getIndex(3, j)].addA(alphaValues[j][3]);
				dest += pitch;
			}

			if(nonOpaquePunchThroughAlpha)
			{
				decodePunchThroughAlphaBlock(destStart, x, y, w, h, pitch);
			}
		}

		void decodePlanarBlock(unsigned char *dest, int x, int y, int w, int h, int pitch, unsigned char alphaValues[4][4]) const
		{
			int ro = extend_6to8bits(RO);
			int go = extend_7to8bits(GO1 << 6 | GO2);
			int bo = extend_6to8bits(BO1 << 5 | BO2 << 3 | BO3a << 1 | BO3b);

			int rh = extend_6to8bits(RH1 << 1 | RH2);
			int gh = extend_7to8bits(GH);
			int bh = extend_6to8bits(BHa << 5 | BHb);

			int rv = extend_6to8bits(RVa << 3 | RVb);
			int gv = extend_7to8bits(GVa << 2 | GVb);
			int bv = extend_6to8bits(BV);

			for(int j = 0; j < 4 && (y + j) < h; j++)
			{
				int ry = j * (rv - ro) + 2;
				int gy = j * (gv - go) + 2;
				int by = j * (bv - bo) + 2;
				for(int i = 0; i < 4 && (x + i) < w; i++)
				{
					((bgra8*)(dest))[i].set(((i * (rh - ro) + ry) >> 2) + ro,
						((i * (gh - go) + gy) >> 2) + go,
						((i * (bh - bo) + by) >> 2) + bo,
						alphaValues[j][i]);
				}
				dest += pitch;
			}
		}

		// Index for individual, differential, H and T modes
		inline int getIndex(int x, int y) const
		{
			int bitIndex = x * 4 + y;
			int bitOffset = bitIndex & 7;
			int lsb = (pixelIndexLSB[1 - (bitIndex >> 3)] >> bitOffset) & 1;
			int msb = (pixelIndexMSB[1 - (bitIndex >> 3)] >> bitOffset) & 1;

			return (msb << 1) | lsb;
		}

		void decodePunchThroughAlphaBlock(unsigned char *dest, int x, int y, int w, int h, int pitch) const
		{
			for(int j = 0; j < 4 && (y + j) < h; j++)
			{
				for(int i = 0; i < 4 && (x + i) < w; i++)
				{
					if(getIndex(i, j) == 2) //  msb == 1 && lsb == 0
					{
						((bgra8*)dest)[i].set(0, 0, 0, 0);
					}
				}
				dest += pitch;
			}
		}

		// Single channel utility functions
		inline int getSingleChannel(int x, int y, bool isSigned, bool isEAC) const
		{
			int codeword = isSigned ? signed_base_codeword : base_codeword;
			return isEAC ?
			       ((multiplier == 0) ?
			        (codeword * 8 + 4 + getSingleChannelModifier(x, y)) :
			        (codeword * 8 + 4 + getSingleChannelModifier(x, y) * multiplier * 8)) :
			       codeword + getSingleChannelModifier(x, y) * multiplier;
		}

		inline int getSingleChannelIndex(int x, int y) const
		{
			switch(x * 4 + y)
			{
			case 0: return ma;
			case 1: return mb;
			case 2: return mc1 << 1 | mc2;
			case 3: return md;
			case 4: return me;
			case 5: return mf1 << 2 | mf2;
			case 6: return mg;
			case 7: return mh;
			case 8: return mi;
			case 9: return mj;
			case 10: return mk1 << 1 | mk2;
			case 11: return ml;
			case 12: return mm;
			case 13: return mn1 << 2 | mn2;
			case 14: return mo;
			default: return mp; // 15
			}
		}

		inline int getSingleChannelModifier(int x, int y) const
		{
			static const int modifierTable[16][8] = { { -3, -6, -9, -15, 2, 5, 8, 14 },
			{ -3, -7, -10, -13, 2, 6, 9, 12 },
			{ -2, -5, -8, -13, 1, 4, 7, 12 },
			{ -2, -4, -6, -13, 1, 3, 5, 12 },
			{ -3, -6, -8, -12, 2, 5, 7, 11 },
			{ -3, -7, -9, -11, 2, 6, 8, 10 },
			{ -4, -7, -8, -11, 3, 6, 7, 10 },
			{ -3, -5, -8, -11, 2, 4, 7, 10 },
			{ -2, -6, -8, -10, 1, 5, 7, 9 },
			{ -2, -5, -8, -10, 1, 4, 7, 9 },
			{ -2, -4, -8, -10, 1, 3, 7, 9 },
			{ -2, -5, -7, -10, 1, 4, 6, 9 },
			{ -3, -4, -7, -10, 2, 3, 6, 9 },
			{ -1, -2, -3, -10, 0, 1, 2, 9 },
			{ -4, -6, -8, -9, 3, 5, 7, 8 },
			{ -3, -5, -7, -9, 2, 4, 6, 8 } };

			return modifierTable[table_index][getSingleChannelIndex(x, y)];
		}
	};
}

// Decodes 1 to 4 channel images to 8 bit output
bool ETC_Decoder::Decode(const unsigned char* src, unsigned char *dst, int w, int h, int dstW, int dstH, int dstPitch, int dstBpp, InputType inputType)
{
	const ETC2* sources[2];
	sources[0] = (const ETC2*)src;

	unsigned char alphaValues[4][4] = { { 255, 255, 255, 255 }, { 255, 255, 255, 255 }, { 255, 255, 255, 255 }, { 255, 255, 255, 255 } };

	switch(inputType)
	{
	case ETC_R_SIGNED:
	case ETC_R_UNSIGNED:
		for(int y = 0; y < h; y += 4)
		{
			unsigned char *dstRow = dst + (y * dstPitch);
			for(int x = 0; x < w; x += 4, sources[0]++)
			{
				ETC2::DecodeBlock(sources, dstRow + (x * dstBpp), 1, x, y, dstW, dstH, dstPitch, inputType == ETC_R_SIGNED, true);
			}
		}
		break;
	case ETC_RG_SIGNED:
	case ETC_RG_UNSIGNED:
		sources[1] = sources[0] + 1;
		for(int y = 0; y < h; y += 4)
		{
			unsigned char *dstRow = dst + (y * dstPitch);
			for(int x = 0; x < w; x += 4, sources[0] += 2, sources[1] += 2)
			{
				ETC2::DecodeBlock(sources, dstRow + (x * dstBpp), 2, x, y, dstW, dstH, dstPitch, inputType == ETC_RG_SIGNED, true);
			}
		}
		break;
	case ETC_RGB:
	case ETC_RGB_PUNCHTHROUGH_ALPHA:
		for(int y = 0; y < h; y += 4)
		{
			unsigned char *dstRow = dst + (y * dstPitch);
			for(int x = 0; x < w; x += 4, sources[0]++)
			{
				sources[0]->decodeBlock(dstRow + (x * dstBpp), x, y, dstW, dstH, dstPitch, alphaValues, inputType == ETC_RGB_PUNCHTHROUGH_ALPHA);
			}
		}
		break;
	case ETC_RGBA:
		for(int y = 0; y < h; y += 4)
		{
			unsigned char *dstRow = dst + (y * dstPitch);
			for(int x = 0; x < w; x += 4)
			{
				// Decode Alpha
				ETC2::DecodeBlock(&sources[0], &(alphaValues[0][0]), 1, x, y, dstW, dstH, 4, false, false);
				sources[0]++; // RGBA packets are 128 bits, so move on to the next 64 bit packet to decode the RGB color

				// Decode RGB
				sources[0]->decodeBlock(dstRow + (x * dstBpp), x, y, dstW, dstH, dstPitch, alphaValues, false);
				sources[0]++;
			}
		}
		break;
	default:
		return false;
	}

	return true;
}