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// Copyright (c) the JPEG XL Project Authors. All rights reserved.
//
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
#ifndef LIB_JXL_AC_STRATEGY_H_
#define LIB_JXL_AC_STRATEGY_H_
#include <jxl/memory_manager.h>
#include <cstddef>
#include <cstdint>
#include <hwy/base.h> // kMaxVectorSize
#include "lib/jxl/base/compiler_specific.h"
#include "lib/jxl/base/rect.h"
#include "lib/jxl/base/status.h"
#include "lib/jxl/coeff_order_fwd.h"
#include "lib/jxl/frame_dimensions.h"
#include "lib/jxl/image.h"
#include "lib/jxl/image_ops.h"
// Defines the different kinds of transforms, and heuristics to choose between
// them.
// `AcStrategy` represents what transform should be used, and which sub-block of
// that transform we are currently in. Note that DCT4x4 is applied on all four
// 4x4 sub-blocks of an 8x8 block.
// `AcStrategyImage` defines which strategy should be used for each 8x8 block
// of the image. The highest 4 bits represent the strategy to be used, the
// lowest 4 represent the index of the block inside that strategy.
namespace jxl {
// Raw strategy types.
enum class AcStrategyType : uint32_t {
// Regular block size DCT
DCT = 0,
// Encode pixels without transforming
IDENTITY = 1,
// Use 2-by-2 DCT
DCT2X2 = 2,
// Use 4-by-4 DCT
DCT4X4 = 3,
// Use 16-by-16 DCT
DCT16X16 = 4,
// Use 32-by-32 DCT
DCT32X32 = 5,
// Use 16-by-8 DCT
DCT16X8 = 6,
// Use 8-by-16 DCT
DCT8X16 = 7,
// Use 32-by-8 DCT
DCT32X8 = 8,
// Use 8-by-32 DCT
DCT8X32 = 9,
// Use 32-by-16 DCT
DCT32X16 = 10,
// Use 16-by-32 DCT
DCT16X32 = 11,
// 4x8 and 8x4 DCT
DCT4X8 = 12,
DCT8X4 = 13,
// Corner-DCT.
AFV0 = 14,
AFV1 = 15,
AFV2 = 16,
AFV3 = 17,
// Larger DCTs
DCT64X64 = 18,
DCT64X32 = 19,
DCT32X64 = 20,
// No transforms smaller than 64x64 are allowed below.
DCT128X128 = 21,
DCT128X64 = 22,
DCT64X128 = 23,
DCT256X256 = 24,
DCT256X128 = 25,
DCT128X256 = 26
};
class AcStrategy {
public:
// Extremal values for the number of blocks/coefficients of a single strategy.
static constexpr size_t kMaxCoeffBlocks = 32;
static constexpr size_t kMaxBlockDim = kBlockDim * kMaxCoeffBlocks;
// Maximum number of coefficients in a block. Guaranteed to be a multiple of
// the vector size.
static constexpr size_t kMaxCoeffArea = kMaxBlockDim * kMaxBlockDim;
static_assert((kMaxCoeffArea * sizeof(float)) % hwy::kMaxVectorSize == 0,
"Coefficient area is not a multiple of vector size");
static constexpr uint8_t kNumValidStrategies =
static_cast<uint8_t>(AcStrategyType::DCT128X256) + 1;
static constexpr uint32_t TypeBit(const AcStrategyType type) {
return 1u << static_cast<uint32_t>(type);
}
// Returns true if this block is the first 8x8 block (i.e. top-left) of a
// possibly multi-block strategy.
JXL_INLINE bool IsFirstBlock() const { return is_first_; }
JXL_INLINE bool IsMultiblock() const {
constexpr uint32_t bits =
TypeBit(AcStrategyType::DCT16X16) | TypeBit(AcStrategyType::DCT32X32) |
TypeBit(AcStrategyType::DCT16X8) | TypeBit(AcStrategyType::DCT8X16) |
TypeBit(AcStrategyType::DCT32X8) | TypeBit(AcStrategyType::DCT8X32) |
TypeBit(AcStrategyType::DCT16X32) | TypeBit(AcStrategyType::DCT32X16) |
TypeBit(AcStrategyType::DCT32X64) | TypeBit(AcStrategyType::DCT64X32) |
TypeBit(AcStrategyType::DCT64X64) | TypeBit(AcStrategyType::DCT64X128) |
TypeBit(AcStrategyType::DCT128X64) |
TypeBit(AcStrategyType::DCT128X128) |
TypeBit(AcStrategyType::DCT128X256) |
TypeBit(AcStrategyType::DCT256X128) |
TypeBit(AcStrategyType::DCT256X256);
return ((1u << static_cast<uint32_t>(Strategy())) & bits) != 0;
}
// Returns the raw strategy value. Should only be used for tokenization.
JXL_INLINE uint8_t RawStrategy() const {
return static_cast<uint8_t>(strategy_);
}
JXL_INLINE AcStrategyType Strategy() const { return strategy_; }
// Inverse check
static JXL_INLINE constexpr bool IsRawStrategyValid(int raw_strategy) {
return raw_strategy < kNumValidStrategies && raw_strategy >= 0;
}
static JXL_INLINE AcStrategy FromRawStrategy(uint8_t raw_strategy) {
return FromRawStrategy(static_cast<AcStrategyType>(raw_strategy));
}
static JXL_INLINE AcStrategy FromRawStrategy(AcStrategyType raw_strategy) {
JXL_DASSERT(IsRawStrategyValid(static_cast<uint32_t>(raw_strategy)));
return AcStrategy(raw_strategy, /*is_first=*/true);
}
// "Natural order" means the order of increasing of "anisotropic" frequency of
// continuous version of DCT basis.
// Round-trip, for any given strategy s:
// X = NaturalCoeffOrder(s)[NaturalCoeffOrderLutN(s)[X]]
// X = NaturalCoeffOrderLut(s)[NaturalCoeffOrderN(s)[X]]
void ComputeNaturalCoeffOrder(coeff_order_t* order) const;
void ComputeNaturalCoeffOrderLut(coeff_order_t* lut) const;
// Number of 8x8 blocks that this strategy will cover. 0 for non-top-left
// blocks inside a multi-block transform.
JXL_INLINE size_t covered_blocks_x() const {
static constexpr uint8_t kLut[] = {1, 1, 1, 1, 2, 4, 1, 2, 1,
4, 2, 4, 1, 1, 1, 1, 1, 1,
8, 4, 8, 16, 8, 16, 32, 16, 32};
static_assert(sizeof(kLut) / sizeof(*kLut) == kNumValidStrategies,
"Update LUT");
return kLut[static_cast<size_t>(strategy_)];
}
JXL_INLINE size_t covered_blocks_y() const {
static constexpr uint8_t kLut[] = {1, 1, 1, 1, 2, 4, 2, 1, 4,
1, 4, 2, 1, 1, 1, 1, 1, 1,
8, 8, 4, 16, 16, 8, 32, 32, 16};
static_assert(sizeof(kLut) / sizeof(*kLut) == kNumValidStrategies,
"Update LUT");
return kLut[static_cast<size_t>(strategy_)];
}
JXL_INLINE size_t log2_covered_blocks() const {
static constexpr uint8_t kLut[] = {0, 0, 0, 0, 2, 4, 1, 1, 2,
2, 3, 3, 0, 0, 0, 0, 0, 0,
6, 5, 5, 8, 7, 7, 10, 9, 9};
static_assert(sizeof(kLut) / sizeof(*kLut) == kNumValidStrategies,
"Update LUT");
return kLut[static_cast<size_t>(strategy_)];
}
private:
friend class AcStrategyRow;
JXL_INLINE AcStrategy(AcStrategyType strategy, bool is_first)
: strategy_(strategy), is_first_(is_first) {
JXL_DASSERT(IsMultiblock() || is_first == true);
}
AcStrategyType strategy_;
bool is_first_;
};
// Class to use a certain row of the AC strategy.
class AcStrategyRow {
public:
explicit AcStrategyRow(const uint8_t* row) : row_(row) {}
AcStrategy operator[](size_t x) const {
AcStrategyType strategy = static_cast<AcStrategyType>(row_[x] >> 1);
bool is_first = static_cast<bool>(row_[x] & 1);
return AcStrategy(strategy, is_first);
}
private:
const uint8_t* JXL_RESTRICT row_;
};
class AcStrategyImage {
public:
AcStrategyImage() = default;
static StatusOr<AcStrategyImage> Create(JxlMemoryManager* memory_manager,
size_t xsize, size_t ysize);
AcStrategyImage(AcStrategyImage&&) = default;
AcStrategyImage& operator=(AcStrategyImage&&) = default;
void FillDCT8(const Rect& rect) {
FillPlane<uint8_t>((static_cast<uint8_t>(AcStrategyType::DCT) << 1) | 1,
&layers_, rect);
}
void FillDCT8() { FillDCT8(Rect(layers_)); }
void FillInvalid() { FillImage(INVALID, &layers_); }
Status Set(size_t x, size_t y, AcStrategyType type) {
#if (JXL_IS_DEBUG_BUILD)
AcStrategy acs = AcStrategy::FromRawStrategy(type);
JXL_DASSERT(y + acs.covered_blocks_y() <= layers_.ysize());
JXL_DASSERT(x + acs.covered_blocks_x() <= layers_.xsize());
#endif
JXL_RETURN_IF_ERROR(SetNoBoundsCheck(x, y, type, /*check=*/false));
return true;
}
Status SetNoBoundsCheck(size_t x, size_t y, AcStrategyType type,
bool check = true) {
AcStrategy acs = AcStrategy::FromRawStrategy(type);
for (size_t iy = 0; iy < acs.covered_blocks_y(); iy++) {
for (size_t ix = 0; ix < acs.covered_blocks_x(); ix++) {
size_t pos = (y + iy) * stride_ + x + ix;
if (check && row_[pos] != INVALID) {
return JXL_FAILURE("Invalid AC strategy: block overlap");
}
row_[pos] =
(static_cast<uint8_t>(type) << 1) | ((iy | ix) == 0 ? 1 : 0);
}
}
return true;
}
bool IsValid(size_t x, size_t y) { return row_[y * stride_ + x] != INVALID; }
AcStrategyRow ConstRow(size_t y, size_t x_prefix = 0) const {
return AcStrategyRow(layers_.ConstRow(y) + x_prefix);
}
AcStrategyRow ConstRow(const Rect& rect, size_t y) const {
return ConstRow(rect.y0() + y, rect.x0());
}
size_t PixelsPerRow() const { return layers_.PixelsPerRow(); }
size_t xsize() const { return layers_.xsize(); }
size_t ysize() const { return layers_.ysize(); }
// Count the number of blocks of a given type.
size_t CountBlocks(AcStrategyType type) const;
JxlMemoryManager* memory_manager() const { return layers_.memory_manager(); }
private:
ImageB layers_;
uint8_t* JXL_RESTRICT row_;
size_t stride_;
// A value that does not represent a valid combined AC strategy
// value. Used as a sentinel.
static constexpr uint8_t INVALID = 0xFF;
};
} // namespace jxl
#endif // LIB_JXL_AC_STRATEGY_H_