/*
* Copyright 2020 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#include "src/core/SkCompressedDataUtils.h"
#include "include/core/SkBitmap.h"
#include "include/core/SkColorPriv.h"
#include "include/core/SkData.h"
#include "include/private/SkColorData.h"
#include "include/private/SkTPin.h"
#include "src/core/SkMathPriv.h"
#include "src/core/SkMipmap.h"
struct ETC1Block {
uint32_t fHigh;
uint32_t fLow;
};
constexpr uint32_t kFlipBit = 0x1; // set -> T/B sub-blocks; not-set -> L/R sub-blocks
constexpr uint32_t kDiffBit = 0x2; // set -> differential; not-set -> individual
static inline int extend_4To8bits(int b) {
int c = b & 0xf;
return (c << 4) | c;
}
static inline int extend_5To8bits(int b) {
int c = b & 0x1f;
return (c << 3) | (c >> 2);
}
static inline int extend_5plus3To8Bits(int base, int diff) {
static const int kLookup[8] = { 0, 1, 2, 3, -4, -3, -2, -1 };
return extend_5To8bits((0x1f & base) + kLookup[0x7 & diff]);
}
static const int kNumETC1ModifierTables = 8;
static const int kNumETC1PixelIndices = 4;
// The index of each row in this table is the ETC1 table codeword
// The index of each column in this table is the ETC1 pixel index value
static const int kETC1ModifierTables[kNumETC1ModifierTables][kNumETC1PixelIndices] = {
/* 0 */ { 2, 8, -2, -8 },
/* 1 */ { 5, 17, -5, -17 },
/* 2 */ { 9, 29, -9, -29 },
/* 3 */ { 13, 42, -13, -42 },
/* 4 */ { 18, 60, -18, -60 },
/* 5 */ { 24, 80, -24, -80 },
/* 6 */ { 33, 106, -33, -106 },
/* 7 */ { 47, 183, -47, -183 }
};
static int num_4x4_blocks(int size) {
return ((size + 3) & ~3) >> 2;
}
// Return which sub-block a given x,y location in the overall 4x4 block belongs to
static int xy_to_subblock_index(int x, int y, bool flip) {
SkASSERT(x >= 0 && x < 4);
SkASSERT(y >= 0 && y < 4);
if (flip) {
return y < 2 ? 0 : 1; // sub-block 1 is on top of sub-block 2
} else {
return x < 2 ? 0 : 1; // sub-block 1 is to the left of sub-block 2
}
}
struct IColor {
int fR, fG, fB;
};
static SkPMColor add_delta_and_clamp(const IColor& col, int delta) {
int r8 = SkTPin(col.fR + delta, 0, 255);
int g8 = SkTPin(col.fG + delta, 0, 255);
int b8 = SkTPin(col.fB + delta, 0, 255);
return SkPackARGB32(0xFF, r8, g8, b8);
}
static bool decompress_etc1(SkISize dimensions, const uint8_t* srcData, SkBitmap* dst) {
const ETC1Block* srcBlocks = reinterpret_cast<const ETC1Block*>(srcData);
int numXBlocks = num_4x4_blocks(dimensions.width());
int numYBlocks = num_4x4_blocks(dimensions.height());
for (int y = 0; y < numYBlocks; ++y) {
for (int x = 0; x < numXBlocks; ++x) {
const ETC1Block* curBlock1 = &srcBlocks[y * numXBlocks + x];
uint32_t high = SkBSwap32(curBlock1->fHigh);
uint32_t low = SkBSwap32(curBlock1->fLow);
bool flipped = SkToBool(high & kFlipBit);
bool differential = SkToBool(high & kDiffBit);
IColor colors[2];
if (differential) {
colors[0].fR = extend_5To8bits(high >> 27);
colors[1].fR = extend_5plus3To8Bits(high >> 27, high >> 24);
colors[0].fG = extend_5To8bits(high >> 19);
colors[1].fG = extend_5plus3To8Bits(high >> 19, high >> 16);
colors[0].fB = extend_5To8bits(high >> 11);
colors[1].fB = extend_5plus3To8Bits(high >> 11, high >> 8);
} else {
colors[0].fR = extend_4To8bits(high >> 28);
colors[1].fR = extend_4To8bits(high >> 24);
colors[0].fG = extend_4To8bits(high >> 20);
colors[1].fG = extend_4To8bits(high >> 16);
colors[0].fB = extend_4To8bits(high >> 12);
colors[1].fB = extend_4To8bits(high >> 8);
}
int tableIndex0 = (high >> 5) & 0x7;
int tableIndex1 = (high >> 2) & 0x7;
const int* tables[2] = {
kETC1ModifierTables[tableIndex0],
kETC1ModifierTables[tableIndex1]
};
int baseShift = 0;
int offsetX = 4 * x, offsetY = 4 * y;
for (int i = 0; i < 4; ++i, ++baseShift) {
for (int j = 0; j < 4; ++j) {
if (offsetX + j >= dst->width() || offsetY + i >= dst->height()) {
// This can happen for the topmost levels of a mipmap and for
// non-multiple of 4 textures
continue;
}
int subBlockIndex = xy_to_subblock_index(j, i, flipped);
int pixelIndex = ((low >> (baseShift+(j*4))) & 0x1) |
(low >> (baseShift+(j*4)+15) & 0x2);
SkASSERT(subBlockIndex == 0 || subBlockIndex == 1);
SkASSERT(pixelIndex >= 0 && pixelIndex < 4);
int delta = tables[subBlockIndex][pixelIndex];
*dst->getAddr32(offsetX + j, offsetY + i) =
add_delta_and_clamp(colors[subBlockIndex], delta);
}
}
}
}
return true;
}
//------------------------------------------------------------------------------------------------
struct BC1Block {
uint16_t fColor0;
uint16_t fColor1;
uint32_t fIndices;
};
static SkPMColor from565(uint16_t rgb565) {
uint8_t r8 = SkR16ToR32((rgb565 >> 11) & 0x1F);
uint8_t g8 = SkG16ToG32((rgb565 >> 5) & 0x3F);
uint8_t b8 = SkB16ToB32(rgb565 & 0x1F);
return SkPackARGB32(0xFF, r8, g8, b8);
}
// return t*col0 + (1-t)*col1
static SkPMColor lerp(float t, SkPMColor col0, SkPMColor col1) {
SkASSERT(SkGetPackedA32(col0) == 0xFF && SkGetPackedA32(col1) == 0xFF);
// TODO: given 't' is only either 1/3 or 2/3 this could be done faster
uint8_t r8 = SkScalarRoundToInt(t * SkGetPackedR32(col0) + (1.0f - t) * SkGetPackedR32(col1));
uint8_t g8 = SkScalarRoundToInt(t * SkGetPackedG32(col0) + (1.0f - t) * SkGetPackedG32(col1));
uint8_t b8 = SkScalarRoundToInt(t * SkGetPackedB32(col0) + (1.0f - t) * SkGetPackedB32(col1));
return SkPackARGB32(0xFF, r8, g8, b8);
}
static bool decompress_bc1(SkISize dimensions, const uint8_t* srcData,
bool isOpaque, SkBitmap* dst) {
const BC1Block* srcBlocks = reinterpret_cast<const BC1Block*>(srcData);
int numXBlocks = num_4x4_blocks(dimensions.width());
int numYBlocks = num_4x4_blocks(dimensions.height());
SkPMColor colors[4];
for (int y = 0; y < numYBlocks; ++y) {
for (int x = 0; x < numXBlocks; ++x) {
const BC1Block* curBlock = &srcBlocks[y * numXBlocks + x];
colors[0] = from565(curBlock->fColor0);
colors[1] = from565(curBlock->fColor1);
if (curBlock->fColor0 <= curBlock->fColor1) { // signal for a transparent block
colors[2] = SkPackARGB32(
0xFF,
(SkGetPackedR32(colors[0]) + SkGetPackedR32(colors[1])) >> 1,
(SkGetPackedG32(colors[0]) + SkGetPackedG32(colors[1])) >> 1,
(SkGetPackedB32(colors[0]) + SkGetPackedB32(colors[1])) >> 1);
// The opacity of the overall texture trumps the per-block transparency
colors[3] = SkPackARGB32(isOpaque ? 0xFF : 0, 0, 0, 0);
} else {
colors[2] = lerp(2.0f/3.0f, colors[0], colors[1]);
colors[3] = lerp(1.0f/3.0f, colors[0], colors[1]);
}
int shift = 0;
int offsetX = 4 * x, offsetY = 4 * y;
for (int i = 0; i < 4; ++i) {
for (int j = 0; j < 4; ++j, shift += 2) {
if (offsetX + j >= dst->width() || offsetY + i >= dst->height()) {
// This can happen for the topmost levels of a mipmap and for
// non-multiple of 4 textures
continue;
}
int index = (curBlock->fIndices >> shift) & 0x3;
*dst->getAddr32(offsetX + j, offsetY + i) = colors[index];
}
}
}
}
return true;
}
bool SkDecompress(sk_sp<SkData> data,
SkISize dimensions,
SkImage::CompressionType compressionType,
SkBitmap* dst) {
using Type = SkImage::CompressionType;
const uint8_t* bytes = data->bytes();
switch (compressionType) {
case Type::kNone: return false;
case Type::kETC2_RGB8_UNORM: return decompress_etc1(dimensions, bytes, dst);
case Type::kBC1_RGB8_UNORM: return decompress_bc1(dimensions, bytes, true, dst);
case Type::kBC1_RGBA8_UNORM: return decompress_bc1(dimensions, bytes, false, dst);
}
SkUNREACHABLE;
return false;
}
size_t SkCompressedDataSize(SkImage::CompressionType type, SkISize dimensions,
SkTArray<size_t>* individualMipOffsets, bool mipMapped) {
SkASSERT(!individualMipOffsets || !individualMipOffsets->count());
int numMipLevels = 1;
if (mipMapped) {
numMipLevels = SkMipmap::ComputeLevelCount(dimensions.width(), dimensions.height()) + 1;
}
size_t totalSize = 0;
switch (type) {
case SkImage::CompressionType::kNone:
break;
case SkImage::CompressionType::kETC2_RGB8_UNORM:
case SkImage::CompressionType::kBC1_RGB8_UNORM:
case SkImage::CompressionType::kBC1_RGBA8_UNORM: {
for (int i = 0; i < numMipLevels; ++i) {
int numBlocks = num_4x4_blocks(dimensions.width()) *
num_4x4_blocks(dimensions.height());
if (individualMipOffsets) {
individualMipOffsets->push_back(totalSize);
}
static_assert(sizeof(ETC1Block) == sizeof(BC1Block));
totalSize += numBlocks * sizeof(ETC1Block);
dimensions = {std::max(1, dimensions.width()/2), std::max(1, dimensions.height()/2)};
}
break;
}
}
return totalSize;
}
size_t SkCompressedBlockSize(SkImage::CompressionType type) {
switch (type) {
case SkImage::CompressionType::kNone:
return 0;
case SkImage::CompressionType::kETC2_RGB8_UNORM:
return sizeof(ETC1Block);
case SkImage::CompressionType::kBC1_RGB8_UNORM:
case SkImage::CompressionType::kBC1_RGBA8_UNORM:
return sizeof(BC1Block);
}
SkUNREACHABLE;
}
size_t SkCompressedFormatDataSize(SkImage::CompressionType compressionType,
SkISize dimensions, bool mipMapped) {
return SkCompressedDataSize(compressionType, dimensions, nullptr, mipMapped);
}