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#include "ETC2Decompression.h"
// Utilities
template<typename T>
static inline T InRange (T v, T a, T b)
{
return a <= v && v <= b;
}
template<typename T>
static inline T Clamp (T v, T a, T b)
{
if (v < a) return a;
else if (v > b) return b;
else return v;
}
static inline int DivRoundUp (int a, int b)
{
return a/b + ((a%b) ? 1 : 0);
}
static inline UInt32 GetSingleBit (UInt64 src, int bit)
{
return (src >> bit) & 1;
}
static inline UInt32 GetBitRange (UInt64 src, int low, int high)
{
int numBits = (high-low) + 1;
return (src >> low) & ((1<<numBits)-1);
}
static inline UInt8 ExtendTo8 (UInt8 src, UInt32 fromBits)
{
return (src << (8-fromBits)) | (src >> (2*fromBits - 8));
}
static inline SInt8 Extend3BitSignedDelta (UInt8 src)
{
bool isNeg = (src & (1<<2)) != 0;
return (SInt8)((isNeg ? ~((1<<3)-1) : 0) | src);
}
static inline UInt16 Extend11To16 (UInt16 src)
{
return (src << 5) | (src >> 6);
}
static inline SInt16 Extend11To16WithSign (SInt16 src)
{
if (src < 0)
return -(SInt16)Extend11To16(-src);
else
return (SInt16)Extend11To16(src);
}
// Block access utilities
static inline UInt64 Get64BitBlock (const UInt8* src, int blockNdx)
{
UInt64 block = 0;
for (int i = 0; i < 8; i++)
block = (block << 8ull) | (UInt64)(src[blockNdx*8+i]);
return block;
}
static inline UInt64 Get128BitBlockStart (const UInt8* src, int blockNdx)
{
return Get64BitBlock(src, 2*blockNdx);
}
static inline UInt64 Get128BitBlockEnd (const UInt8* src, int blockNdx)
{
return Get64BitBlock(src, 2*blockNdx + 1);
}
// Block decompression routines
static void DecompressETC2Block (UInt64 src, UInt8 dst[kETC2UncompressedBlockSizeRGB8], UInt8 alphaDst[kETC2UncompressedBlockSizeA8], bool alphaMode)
{
typedef enum BlockMode_e
{
kBlockModeIndividual = 0,
kBlockModeDifferential,
kBlockModeT,
kBlockModeH,
kBlockModePlanar,
kBlockModeCount
} BlockMode;
int diffOpaqueBit = (int)GetSingleBit(src, 33);
SInt8 selBR = (SInt8)GetBitRange(src, 59, 63); // 5 bits.
SInt8 selBG = (SInt8)GetBitRange(src, 51, 55);
SInt8 selBB = (SInt8)GetBitRange(src, 43, 47);
SInt8 selDR = Extend3BitSignedDelta((UInt8)GetBitRange(src, 56, 58)); // 3 bits.
SInt8 selDG = Extend3BitSignedDelta((UInt8)GetBitRange(src, 48, 50));
SInt8 selDB = Extend3BitSignedDelta((UInt8)GetBitRange(src, 40, 42));
BlockMode mode;
if (!alphaMode && diffOpaqueBit == 0)
mode = kBlockModeIndividual;
else if (!InRange(selBR + selDR, 0, 31))
mode = kBlockModeT;
else if (!InRange(selBG + selDG, 0, 31))
mode = kBlockModeH;
else if (!InRange(selBB + selDB, 0, 31))
mode = kBlockModePlanar;
else
mode = kBlockModeDifferential;
if (mode == kBlockModeIndividual || mode == kBlockModeDifferential)
{
// A lot of logic is shared between individual and differential mode
static const int modifierLUT[8][4] =
{
// 00 01 10 11
{ 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 }
};
int flipBit = (int)GetSingleBit(src, 32);
UInt32 table[2] = { GetBitRange(src, 37, 39), GetBitRange(src, 34, 36) };
UInt8 baseR[2];
UInt8 baseG[2];
UInt8 baseB[2];
// Base values per mode
if (mode == kBlockModeIndividual)
{
baseR[0] = ExtendTo8((UInt8)GetBitRange(src, 60, 63), 4);
baseR[1] = ExtendTo8((UInt8)GetBitRange(src, 56, 59), 4);
baseG[0] = ExtendTo8((UInt8)GetBitRange(src, 52, 55), 4);
baseG[1] = ExtendTo8((UInt8)GetBitRange(src, 48, 51), 4);
baseB[0] = ExtendTo8((UInt8)GetBitRange(src, 44, 47), 4);
baseB[1] = ExtendTo8((UInt8)GetBitRange(src, 40, 43), 4);
}
else
{
baseR[0] = ExtendTo8(selBR, 5);
baseG[0] = ExtendTo8(selBG, 5);
baseB[0] = ExtendTo8(selBB, 5);
baseR[1] = ExtendTo8((UInt8)(selBR + selDR), 5);
baseG[1] = ExtendTo8((UInt8)(selBG + selDG), 5);
baseB[1] = ExtendTo8((UInt8)(selBB + selDB), 5);
}
for (int pixelNdx = 0; pixelNdx < kETC2BlockHeight*kETC2BlockWidth; pixelNdx++)
{
int x = pixelNdx / kETC2BlockHeight;
int y = pixelNdx % kETC2BlockHeight;
int dstOffset = (y*kETC2BlockWidth + x)*kETC2UncompressedPixelSizeRGB8;
int subBlock = ((flipBit ? y : x) >= 2) ? 1 : 0;
UInt32 tableNdx = table[subBlock];
UInt32 modifierNdx = (GetSingleBit(src, 16+pixelNdx) << 1) | GetSingleBit(src, pixelNdx);
int alphaDstOffset = (y*kETC2BlockWidth + x)*kETC2UncompressedPixelSizeA8; // Only needed for PUNCHTHROUGH version.
if (alphaMode && diffOpaqueBit == 0 && modifierNdx == 2)
{
// If doing PUNCHTHROUGH version (alphaMode), opaque bit may affect colors.
dst[dstOffset+0] = 0;
dst[dstOffset+1] = 0;
dst[dstOffset+2] = 0;
alphaDst[alphaDstOffset] = 0;
}
else
{
int modifier;
// PUNCHTHROUGH version and opaque bit may also affect modifiers.
if (alphaMode && diffOpaqueBit == 0 && (modifierNdx == 0 || modifierNdx == 2))
modifier = 0;
else
modifier = modifierLUT[tableNdx][modifierNdx];
dst[dstOffset+0] = (UInt8)Clamp<int>((int)baseR[subBlock] + modifier, 0, 255);
dst[dstOffset+1] = (UInt8)Clamp<int>((int)baseG[subBlock] + modifier, 0, 255);
dst[dstOffset+2] = (UInt8)Clamp<int>((int)baseB[subBlock] + modifier, 0, 255);
if (alphaMode)
alphaDst[alphaDstOffset] = 255;
}
}
}
else if (mode == kBlockModeT || mode == kBlockModeH)
{
static const int distTable[8] = { 3, 6, 11, 16, 23, 32, 41, 64 };
UInt8 paintR[4];
UInt8 paintG[4];
UInt8 paintB[4];
if (mode == kBlockModeT)
{
// T mode, calculate paint values.
UInt8 R1a = (UInt8)GetBitRange(src, 59, 60);
UInt8 R1b = (UInt8)GetBitRange(src, 56, 57);
UInt8 G1 = (UInt8)GetBitRange(src, 52, 55);
UInt8 B1 = (UInt8)GetBitRange(src, 48, 51);
UInt8 R2 = (UInt8)GetBitRange(src, 44, 47);
UInt8 G2 = (UInt8)GetBitRange(src, 40, 43);
UInt8 B2 = (UInt8)GetBitRange(src, 36, 39);
UInt32 distNdx = (GetBitRange(src, 34, 35) << 1) | GetSingleBit(src, 32);
int dist = distTable[distNdx];
paintR[0] = ExtendTo8(((R1a << 2) | R1b), 4);
paintG[0] = ExtendTo8(G1, 4);
paintB[0] = ExtendTo8(B1, 4);
paintR[2] = ExtendTo8(R2, 4);
paintG[2] = ExtendTo8(G2, 4);
paintB[2] = ExtendTo8(B2, 4);
paintR[1] = (UInt8)Clamp<int>((int)paintR[2] + dist, 0, 255);
paintG[1] = (UInt8)Clamp<int>((int)paintG[2] + dist, 0, 255);
paintB[1] = (UInt8)Clamp<int>((int)paintB[2] + dist, 0, 255);
paintR[3] = (UInt8)Clamp<int>((int)paintR[2] - dist, 0, 255);
paintG[3] = (UInt8)Clamp<int>((int)paintG[2] - dist, 0, 255);
paintB[3] = (UInt8)Clamp<int>((int)paintB[2] - dist, 0, 255);
}
else
{
// H mode, calculate paint values.
UInt8 R1 = (UInt8)GetBitRange(src, 59, 62);
UInt8 G1a = (UInt8)GetBitRange(src, 56, 58);
UInt8 G1b = (UInt8)GetSingleBit(src, 52);
UInt8 B1a = (UInt8)GetSingleBit(src, 51);
UInt8 B1b = (UInt8)GetBitRange(src, 47, 49);
UInt8 R2 = (UInt8)GetBitRange(src, 43, 46);
UInt8 G2 = (UInt8)GetBitRange(src, 39, 42);
UInt8 B2 = (UInt8)GetBitRange(src, 35, 38);
UInt8 baseR[2];
UInt8 baseG[2];
UInt8 baseB[2];
UInt32 baseValue[2];
UInt32 distNdx;
int dist;
baseR[0] = ExtendTo8(R1, 4);
baseG[0] = ExtendTo8(((G1a << 1) | G1b), 4);
baseB[0] = ExtendTo8(((B1a << 3) | B1b), 4);
baseR[1] = ExtendTo8(R2, 4);
baseG[1] = ExtendTo8(G2, 4);
baseB[1] = ExtendTo8(B2, 4);
baseValue[0] = (((UInt32)baseR[0]) << 16) | (((UInt32)baseG[0]) << 8) | baseB[0];
baseValue[1] = (((UInt32)baseR[1]) << 16) | (((UInt32)baseG[1]) << 8) | baseB[1];
distNdx = (GetSingleBit(src, 34) << 2) | (GetSingleBit(src, 32) << 1) | (UInt32)(baseValue[0] >= baseValue[1]);
dist = distTable[distNdx];
paintR[0] = (UInt8)Clamp<int>((int)baseR[0] + dist, 0, 255);
paintG[0] = (UInt8)Clamp<int>((int)baseG[0] + dist, 0, 255);
paintB[0] = (UInt8)Clamp<int>((int)baseB[0] + dist, 0, 255);
paintR[1] = (UInt8)Clamp<int>((int)baseR[0] - dist, 0, 255);
paintG[1] = (UInt8)Clamp<int>((int)baseG[0] - dist, 0, 255);
paintB[1] = (UInt8)Clamp<int>((int)baseB[0] - dist, 0, 255);
paintR[2] = (UInt8)Clamp<int>((int)baseR[1] + dist, 0, 255);
paintG[2] = (UInt8)Clamp<int>((int)baseG[1] + dist, 0, 255);
paintB[2] = (UInt8)Clamp<int>((int)baseB[1] + dist, 0, 255);
paintR[3] = (UInt8)Clamp<int>((int)baseR[1] - dist, 0, 255);
paintG[3] = (UInt8)Clamp<int>((int)baseG[1] - dist, 0, 255);
paintB[3] = (UInt8)Clamp<int>((int)baseB[1] - dist, 0, 255);
}
for (int pixelNdx = 0; pixelNdx < kETC2BlockHeight*kETC2BlockWidth; pixelNdx++)
{
int x = pixelNdx / kETC2BlockHeight;
int y = pixelNdx % kETC2BlockHeight;
int dstOffset = (y*kETC2BlockWidth + x)*kETC2UncompressedPixelSizeRGB8;
UInt32 paintNdx = (GetSingleBit(src, 16+pixelNdx) << 1) | GetSingleBit(src, pixelNdx);
int alphaDstOffset = (y*kETC2BlockWidth + x)*kETC2UncompressedPixelSizeA8; // Only needed for PUNCHTHROUGH version.
if (alphaMode && diffOpaqueBit == 0 && paintNdx == 2)
{
dst[dstOffset+0] = 0;
dst[dstOffset+1] = 0;
dst[dstOffset+2] = 0;
alphaDst[alphaDstOffset] = 0;
}
else
{
dst[dstOffset+0] = (UInt8)Clamp<int>((int)paintR[paintNdx], 0, 255);
dst[dstOffset+1] = (UInt8)Clamp<int>((int)paintG[paintNdx], 0, 255);
dst[dstOffset+2] = (UInt8)Clamp<int>((int)paintB[paintNdx], 0, 255);
if (alphaMode)
alphaDst[alphaDstOffset] = 255;
}
}
}
else
{
// Planar mode.
UInt8 GO1 = (UInt8)GetSingleBit(src, 56);
UInt8 GO2 = (UInt8)GetBitRange(src, 49, 54);
UInt8 BO1 = (UInt8)GetSingleBit(src, 48);
UInt8 BO2 = (UInt8)GetBitRange(src, 43, 44);
UInt8 BO3 = (UInt8)GetBitRange(src, 39, 41);
UInt8 RH1 = (UInt8)GetBitRange(src, 34, 38);
UInt8 RH2 = (UInt8)GetSingleBit(src, 32);
UInt8 RO = ExtendTo8((UInt8)GetBitRange(src, 57, 62), 6);
UInt8 GO = ExtendTo8(((GO1 << 6) | GO2), 7);
UInt8 BO = ExtendTo8(((BO1 << 5) | (BO2 << 3) | BO3), 6);
UInt8 RH = ExtendTo8(((RH1 << 1) | RH2), 6);
UInt8 GH = ExtendTo8((UInt8)GetBitRange(src, 25, 31), 7);
UInt8 BH = ExtendTo8((UInt8)GetBitRange(src, 19, 24), 6);
UInt8 RV = ExtendTo8((UInt8)GetBitRange(src, 13, 18), 6);
UInt8 GV = ExtendTo8((UInt8)GetBitRange(src, 6, 12), 7);
UInt8 BV = ExtendTo8((UInt8)GetBitRange(src, 0, 5), 6);
for (int y = 0; y < 4; y++)
{
for (int x = 0; x < 4; x++)
{
int dstOffset = (y*kETC2BlockWidth + x)*kETC2UncompressedPixelSizeRGB8;
int unclampedR = (x * ((int)RH-(int)RO) + y * ((int)RV-(int)RO) + 4*(int)RO + 2) >> 2;
int unclampedG = (x * ((int)GH-(int)GO) + y * ((int)GV-(int)GO) + 4*(int)GO + 2) >> 2;
int unclampedB = (x * ((int)BH-(int)BO) + y * ((int)BV-(int)BO) + 4*(int)BO + 2) >> 2;
int alphaDstOffset = (y*kETC2BlockWidth + x)*kETC2UncompressedPixelSizeA8; // Only needed for PUNCHTHROUGH version.
dst[dstOffset+0] = (UInt8)Clamp<int>(unclampedR, 0, 255);
dst[dstOffset+1] = (UInt8)Clamp<int>(unclampedG, 0, 255);
dst[dstOffset+2] = (UInt8)Clamp<int>(unclampedB, 0, 255);
if (alphaMode)
alphaDst[alphaDstOffset] = 255;
}
}
}
}
static void DecompressEAC8Block (UInt8 dst[kETC2UncompressedBlockSizeA8], UInt64 src)
{
static const int modifierLUT[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 }
};
UInt8 baseCodeword = (UInt8)GetBitRange(src, 56, 63);
UInt8 multiplier = (UInt8)GetBitRange(src, 52, 55);
UInt32 tableNdx = GetBitRange(src, 48, 51);
for (int pixelNdx = 0; pixelNdx < kETC2BlockHeight*kETC2BlockWidth; pixelNdx++)
{
int x = pixelNdx / kETC2BlockHeight;
int y = pixelNdx % kETC2BlockHeight;
int dstOffset = (y*kETC2BlockWidth + x)*kETC2UncompressedPixelSizeA8;
int pixelBitNdx = 45 - 3*pixelNdx;
UInt32 modifierNdx = (GetSingleBit(src, pixelBitNdx + 2) << 2) | (GetSingleBit(src, pixelBitNdx + 1) << 1) | GetSingleBit(src, pixelBitNdx);
int modifier = modifierLUT[tableNdx][modifierNdx];
dst[dstOffset] = (UInt8)Clamp<int>((int)baseCodeword + (int)multiplier*modifier, 0, 255);
}
}
// Decompression API
void DecompressETC2_RGB8 (UInt8* dst, const UInt8* src, int width, int height)
{
int numBlocksX = DivRoundUp(width, 4);
int numBlocksY = DivRoundUp(height, 4);
int dstPixelSize = kETC2UncompressedPixelSizeRGBA8;
int dstRowPitch = width*dstPixelSize;
for (int blockY = 0; blockY < numBlocksY; blockY++)
{
for (int blockX = 0; blockX < numBlocksX; blockX++)
{
UInt64 compressedBlock = Get64BitBlock(src, blockY*numBlocksX + blockX);
UInt8 uncompressedBlock[kETC2UncompressedBlockSizeRGB8];
DecompressETC2Block(compressedBlock, uncompressedBlock, NULL /* no alpha */, false);
int baseX = blockX*kETC2BlockWidth;
int baseY = blockY*kETC2BlockHeight;
for (int y = 0; y < std::min((int)kETC2BlockHeight, height-baseY); y++)
{
for (int x = 0; x < std::min((int)kETC2BlockWidth, width-baseX); x++)
{
const UInt8* srcPixel = &uncompressedBlock[(y*kETC2BlockWidth + x)*kETC2UncompressedPixelSizeRGB8];
UInt8* dstPixel = dst + (baseY+y)*dstRowPitch + (baseX+x)*dstPixelSize;
dstPixel[0] = srcPixel[0];
dstPixel[1] = srcPixel[1];
dstPixel[2] = srcPixel[2];
dstPixel[3] = 0xff; // Force alpha to 1
}
}
}
}
}
void DecompressETC2_RGB8_A1 (UInt8* dst, const UInt8* src, int width, int height)
{
int numBlocksX = DivRoundUp(width, 4);
int numBlocksY = DivRoundUp(height, 4);
int dstPixelSize = kETC2UncompressedPixelSizeRGBA8;
int dstRowPitch = width*dstPixelSize;
for (int blockY = 0; blockY < numBlocksY; blockY++)
{
for (int blockX = 0; blockX < numBlocksX; blockX++)
{
UInt64 compressedBlockRGBA = Get64BitBlock(src, blockY*numBlocksX + blockX);
UInt8 uncompressedBlockRGB[kETC2UncompressedBlockSizeRGB8];
UInt8 uncompressedBlockAlpha[kETC2UncompressedBlockSizeA8];
DecompressETC2Block(compressedBlockRGBA, uncompressedBlockRGB, uncompressedBlockAlpha, true);
int baseX = blockX*kETC2BlockWidth;
int baseY = blockY*kETC2BlockHeight;
for (int y = 0; y < std::min((int)kETC2BlockHeight, height-baseY); y++)
{
for (int x = 0; x < std::min((int)kETC2BlockWidth, width-baseX); x++)
{
const UInt8* srcPixel = &uncompressedBlockRGB[(y*kETC2BlockWidth + x)*kETC2UncompressedPixelSizeRGB8];
const UInt8* srcPixelAlpha = &uncompressedBlockAlpha[(y*kETC2BlockWidth + x)*kETC2UncompressedPixelSizeA8];
UInt8* dstPixel = dst + (baseY+y)*dstRowPitch + (baseX+x)*dstPixelSize;
dstPixel[0] = srcPixel[0];
dstPixel[1] = srcPixel[1];
dstPixel[2] = srcPixel[2];
dstPixel[3] = srcPixelAlpha[0];
}
}
}
}
}
void DecompressETC2_RGBA8 (UInt8* dst, const UInt8* src, int width, int height)
{
int numBlocksX = DivRoundUp(width, 4);
int numBlocksY = DivRoundUp(height, 4);
int dstPixelSize = kETC2UncompressedPixelSizeRGBA8;
int dstRowPitch = width*dstPixelSize;
for (int blockY = 0; blockY < numBlocksY; blockY++)
{
for (int blockX = 0; blockX < numBlocksX; blockX++)
{
UInt64 compressedBlockAlpha = Get128BitBlockStart(src, blockY*numBlocksX + blockX);
UInt64 compressedBlockRGB = Get128BitBlockEnd(src, blockY*numBlocksX + blockX);
UInt8 uncompressedBlockAlpha[kETC2UncompressedBlockSizeA8];
UInt8 uncompressedBlockRGB[kETC2UncompressedBlockSizeRGB8];
DecompressETC2Block(compressedBlockRGB, uncompressedBlockRGB, NULL /* no alpha */, false);
DecompressEAC8Block(uncompressedBlockAlpha, compressedBlockAlpha);
int baseX = blockX*kETC2BlockWidth;
int baseY = blockY*kETC2BlockHeight;
for (int y = 0; y < std::min((int)kETC2BlockHeight, height-baseY); y++)
{
for (int x = 0; x < std::min((int)kETC2BlockWidth, width-baseX); x++)
{
const UInt8* srcPixelRGB = &uncompressedBlockRGB[(y*kETC2BlockWidth + x)*kETC2UncompressedPixelSizeRGB8];
const UInt8* srcPixelAlpha = &uncompressedBlockAlpha[(y*kETC2BlockWidth + x)*kETC2UncompressedPixelSizeA8];
UInt8* dstPixel = dst + (baseY+y)*dstRowPitch + (baseX+x)*dstPixelSize;
dstPixel[0] = srcPixelRGB[0];
dstPixel[1] = srcPixelRGB[1];
dstPixel[2] = srcPixelRGB[2];
dstPixel[3] = srcPixelAlpha[0];
}
}
}
}
}
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