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// 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 unsigned char clampByte(int value)
{
return static_cast<unsigned char>((value < 0) ? 0 : ((value > 255) ? 255 : value));
}
inline signed char clampSByte(int value)
{
return static_cast<signed char>((value < -128) ? -128 : ((value > 127) ? 127 : value));
}
inline short clampEAC(int value, bool isSigned)
{
short min = isSigned ? -1023 : 0;
short max = isSigned ? 1023 : 2047;
return static_cast<short>(((value < min) ? min : ((value > max) ? max : value)) << 5);
}
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 = clampByte(red);
g = clampByte(green);
b = clampByte(blue);
}
inline void set(int red, int green, int blue, int alpha)
{
r = clampByte(red);
g = clampByte(green);
b = clampByte(blue);
a = clampByte(alpha);
}
const bgra8 &addA(unsigned char 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++)
{
short *sDst = reinterpret_cast<short *>(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 TunusedB : 1;
unsigned char TR1a : 2;
unsigned char TunusedA : 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 HunusedA : 1;
// Byte 2
unsigned char HB1b : 2;
unsigned char HunusedC : 1;
unsigned char HB1a : 1;
unsigned char HG1b : 1;
unsigned char HunusedB : 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 PunusedA : 1;
// Byte 2
unsigned char BO1 : 1;
unsigned char GO2 : 6;
unsigned char PunusedB : 1;
// Byte 3
unsigned char BO3a : 2;
unsigned char PunusedD : 1;
unsigned char BO2 : 2;
unsigned char PunusedC : 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)];
}
};
} // namespace
// 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 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, w, h, 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, w, h, 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, w, h, 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, w, h, 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, w, h, dstPitch, alphaValues, false);
sources[0]++;
}
}
break;
default:
return false;
}
return true;
}