From 26a029d407be480d791972afb5975cf62c9360a6 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Fri, 19 Apr 2024 02:47:55 +0200 Subject: Adding upstream version 124.0.1. Signed-off-by: Daniel Baumann --- third_party/jpeg-xl/lib/jxl/quantizer.h | 180 ++++++++++++++++++++++++++++++++ 1 file changed, 180 insertions(+) create mode 100644 third_party/jpeg-xl/lib/jxl/quantizer.h (limited to 'third_party/jpeg-xl/lib/jxl/quantizer.h') diff --git a/third_party/jpeg-xl/lib/jxl/quantizer.h b/third_party/jpeg-xl/lib/jxl/quantizer.h new file mode 100644 index 0000000000..4e34ac78e8 --- /dev/null +++ b/third_party/jpeg-xl/lib/jxl/quantizer.h @@ -0,0 +1,180 @@ +// 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_QUANTIZER_H_ +#define LIB_JXL_QUANTIZER_H_ + +#include +#include +#include + +#include +#include +#include +#include + +#include "lib/jxl/ac_strategy.h" +#include "lib/jxl/base/bits.h" +#include "lib/jxl/base/compiler_specific.h" +#include "lib/jxl/base/status.h" +#include "lib/jxl/dct_util.h" +#include "lib/jxl/dec_bit_reader.h" +#include "lib/jxl/fields.h" +#include "lib/jxl/image.h" +#include "lib/jxl/quant_weights.h" + +// Quantizes DC and AC coefficients, with separate quantization tables according +// to the quant_kind (which is currently computed from the AC strategy and the +// block index inside that strategy). + +namespace jxl { + +static constexpr int kGlobalScaleDenom = 1 << 16; +static constexpr int kGlobalScaleNumerator = 4096; + +// zero-biases for quantizing channels X, Y, B +static constexpr float kZeroBiasDefault[3] = {0.5f, 0.5f, 0.5f}; + +// Returns adjusted version of a quantized integer, such that its value is +// closer to the expected value of the original. +// The residuals of AC coefficients that we quantize are not uniformly +// distributed. Numerical experiments show that they have a distribution with +// the "shape" of 1/(1+x^2) [up to some coefficients]. This means that the +// expected value of a coefficient that gets quantized to x will not be x +// itself, but (at least with reasonable approximation): +// - 0 if x is 0 +// - x * biases[c] if x is 1 or -1 +// - x - biases[3]/x otherwise +// This follows from computing the distribution of the quantization bias, which +// can be approximated fairly well by /x when |x| is at least two. +static constexpr float kBiasNumerator = 0.145f; + +static constexpr float kDefaultQuantBias[4] = { + 1.0f - 0.05465007330715401f, + 1.0f - 0.07005449891748593f, + 1.0f - 0.049935103337343655f, + 0.145f, +}; + +struct QuantizerParams; + +class Quantizer { + public: + explicit Quantizer(const DequantMatrices* dequant); + Quantizer(const DequantMatrices* dequant, int quant_dc, int global_scale); + + static constexpr int32_t kQuantMax = 256; + + static JXL_INLINE int32_t ClampVal(float val) { + return static_cast( + std::max(1.0f, std::min(val, kQuantMax))); + } + + float ScaleGlobalScale(const float scale) { + int new_global_scale = static_cast(global_scale_ * scale + 0.5f); + float scale_out = new_global_scale * 1.0f / global_scale_; + global_scale_ = new_global_scale; + RecomputeFromGlobalScale(); + return scale_out; + } + + // Recomputes other derived fields after global_scale_ has changed. + void RecomputeFromGlobalScale() { + global_scale_float_ = global_scale_ * (1.0 / kGlobalScaleDenom); + inv_global_scale_ = 1.0 * kGlobalScaleDenom / global_scale_; + inv_quant_dc_ = inv_global_scale_ / quant_dc_; + for (size_t c = 0; c < 3; c++) { + mul_dc_[c] = GetDcStep(c); + inv_mul_dc_[c] = GetInvDcStep(c); + } + } + + // Returns scaling factor such that Scale() * (RawDC() or RawQuantField()) + // pixels yields the same float values returned by GetQuantField. + JXL_INLINE float Scale() const { return global_scale_float_; } + + // Reciprocal of Scale(). + JXL_INLINE float InvGlobalScale() const { return inv_global_scale_; } + + void SetQuantFieldRect(const ImageF& qf, const Rect& rect, + ImageI* JXL_RESTRICT raw_quant_field) const; + + void SetQuantField(float quant_dc, const ImageF& qf, + ImageI* JXL_RESTRICT raw_quant_field); + + void SetQuant(float quant_dc, float quant_ac, + ImageI* JXL_RESTRICT raw_quant_field); + + // Returns the DC quantization base value, which is currently global (not + // adaptive). The actual scale factor used to dequantize pixels in channel c + // is: inv_quant_dc() * dequant_->DCQuant(c). + float inv_quant_dc() const { return inv_quant_dc_; } + + // Dequantize by multiplying with this times dequant_matrix. + float inv_quant_ac(int32_t quant) const { return inv_global_scale_ / quant; } + + QuantizerParams GetParams() const; + + Status Decode(BitReader* reader); + + void DumpQuantizationMap(const ImageI& raw_quant_field) const; + + JXL_INLINE const float* DequantMatrix(size_t quant_kind, size_t c) const { + return dequant_->Matrix(quant_kind, c); + } + + JXL_INLINE const float* InvDequantMatrix(size_t quant_kind, size_t c) const { + return dequant_->InvMatrix(quant_kind, c); + } + + // Calculates DC quantization step. + JXL_INLINE float GetDcStep(size_t c) const { + return inv_quant_dc_ * dequant_->DCQuant(c); + } + JXL_INLINE float GetInvDcStep(size_t c) const { + return dequant_->InvDCQuant(c) * (global_scale_float_ * quant_dc_); + } + + JXL_INLINE const float* MulDC() const { return mul_dc_; } + JXL_INLINE const float* InvMulDC() const { return inv_mul_dc_; } + + JXL_INLINE void ClearDCMul() { + std::fill(mul_dc_, mul_dc_ + 4, 1.f); + std::fill(inv_mul_dc_, inv_mul_dc_ + 4, 1.f); + } + + void ComputeGlobalScaleAndQuant(float quant_dc, float quant_median, + float quant_median_absd); + + private: + float mul_dc_[4]; + float inv_mul_dc_[4]; + + // These are serialized: + int global_scale_; + int quant_dc_; + + // These are derived from global_scale_: + float inv_global_scale_; + float global_scale_float_; // reciprocal of inv_global_scale_ + float inv_quant_dc_; + + float zero_bias_[3]; + const DequantMatrices* dequant_; +}; + +struct QuantizerParams : public Fields { + QuantizerParams() { Bundle::Init(this); } + JXL_FIELDS_NAME(QuantizerParams) + + Status VisitFields(Visitor* JXL_RESTRICT visitor) override; + + uint32_t global_scale; + uint32_t quant_dc; +}; + +} // namespace jxl + +#endif // LIB_JXL_QUANTIZER_H_ -- cgit v1.2.3