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Diffstat (limited to 'third_party/jpeg-xl/lib/jxl/cms/transfer_functions-inl.h')
-rw-r--r-- | third_party/jpeg-xl/lib/jxl/cms/transfer_functions-inl.h | 334 |
1 files changed, 334 insertions, 0 deletions
diff --git a/third_party/jpeg-xl/lib/jxl/cms/transfer_functions-inl.h b/third_party/jpeg-xl/lib/jxl/cms/transfer_functions-inl.h new file mode 100644 index 0000000000..84bcbb45ed --- /dev/null +++ b/third_party/jpeg-xl/lib/jxl/cms/transfer_functions-inl.h @@ -0,0 +1,334 @@ +// 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. + +// Transfer functions for color encodings. + +#if defined(LIB_JXL_CMS_TRANSFER_FUNCTIONS_INL_H_) == defined(HWY_TARGET_TOGGLE) +#ifdef LIB_JXL_CMS_TRANSFER_FUNCTIONS_INL_H_ +#undef LIB_JXL_CMS_TRANSFER_FUNCTIONS_INL_H_ +#else +#define LIB_JXL_CMS_TRANSFER_FUNCTIONS_INL_H_ +#endif + +#include <algorithm> +#include <cmath> +#include <hwy/highway.h> + +#include "lib/jxl/base/compiler_specific.h" +#include "lib/jxl/base/fast_math-inl.h" +#include "lib/jxl/base/rational_polynomial-inl.h" +#include "lib/jxl/base/status.h" +#include "lib/jxl/cms/transfer_functions.h" + +HWY_BEFORE_NAMESPACE(); +namespace jxl { +namespace HWY_NAMESPACE { + +// These templates are not found via ADL. +using hwy::HWY_NAMESPACE::And; +using hwy::HWY_NAMESPACE::AndNot; +using hwy::HWY_NAMESPACE::Gt; +using hwy::HWY_NAMESPACE::IfThenElse; +using hwy::HWY_NAMESPACE::Lt; +using hwy::HWY_NAMESPACE::Or; +using hwy::HWY_NAMESPACE::Sqrt; +using hwy::HWY_NAMESPACE::TableLookupBytes; + +// Definitions for BT.2100-2 transfer functions (used inside/outside SIMD): +// "display" is linear light (nits) normalized to [0, 1]. +// "encoded" is a nonlinear encoding (e.g. PQ) in [0, 1]. +// "scene" is a linear function of photon counts, normalized to [0, 1]. + +// Despite the stated ranges, we need unbounded transfer functions: see +// http://www.littlecms.com/CIC18_UnboundedCMM.pdf. Inputs can be negative or +// above 1 due to chromatic adaptation. To avoid severe round-trip errors caused +// by clamping, we mirror negative inputs via copysign (f(-x) = -f(x), see +// https://developer.apple.com/documentation/coregraphics/cgcolorspace/1644735-extendedsrgb) +// and extend the function domains above 1. + +// Hybrid Log-Gamma. +class TF_HLG : TF_HLG_Base { + public: + // Maximum error 5e-7. + template <class D, class V> + JXL_INLINE V EncodedFromDisplay(D d, V x) const { + const hwy::HWY_NAMESPACE::Rebind<uint32_t, D> du; + const V kSign = BitCast(d, Set(du, 0x80000000u)); + const V original_sign = And(x, kSign); + x = AndNot(kSign, x); // abs + const V below_div12 = Sqrt(Mul(Set(d, 3.0f), x)); + const V e = + MulAdd(Set(d, kA * 0.693147181f), + FastLog2f(d, MulAdd(Set(d, 12), x, Set(d, -kB))), Set(d, kC)); + const V magnitude = IfThenElse(Le(x, Set(d, kDiv12)), below_div12, e); + return Or(AndNot(kSign, magnitude), original_sign); + } +}; + +class TF_709 { + public: + JXL_INLINE double EncodedFromDisplay(const double d) const { + if (d < kThresh) return kMulLow * d; + return kMulHi * std::pow(d, kPowHi) + kSub; + } + + // Maximum error 1e-6. + template <class D, class V> + JXL_INLINE V EncodedFromDisplay(D d, V x) const { + auto low = Mul(Set(d, kMulLow), x); + auto hi = + MulAdd(Set(d, kMulHi), FastPowf(d, x, Set(d, kPowHi)), Set(d, kSub)); + return IfThenElse(Le(x, Set(d, kThresh)), low, hi); + } + + template <class D, class V> + JXL_INLINE V DisplayFromEncoded(D d, V x) const { + auto low = Mul(Set(d, kInvMulLow), x); + auto hi = FastPowf(d, MulAdd(x, Set(d, kInvMulHi), Set(d, kInvAdd)), + Set(d, kInvPowHi)); + return IfThenElse(Lt(x, Set(d, kInvThresh)), low, hi); + } + + private: + static constexpr double kThresh = 0.018; + static constexpr double kMulLow = 4.5; + static constexpr double kMulHi = 1.099; + static constexpr double kPowHi = 0.45; + static constexpr double kSub = -0.099; + + static constexpr double kInvThresh = 0.081; + static constexpr double kInvMulLow = 1 / 4.5; + static constexpr double kInvMulHi = 1 / 1.099; + static constexpr double kInvPowHi = 1 / 0.45; + static constexpr double kInvAdd = 0.099 * kInvMulHi; +}; + +// Perceptual Quantization +class TF_PQ : TF_PQ_Base { + public: + explicit TF_PQ(float display_intensity_target = kDefaultIntensityTarget) + : display_scaling_factor_to_10000_nits_(display_intensity_target * + (1.0f / 10000.0f)), + display_scaling_factor_from_10000_nits_(10000.0f / + display_intensity_target) {} + + // Maximum error 3e-6 + template <class D, class V> + JXL_INLINE V DisplayFromEncoded(D d, V x) const { + const hwy::HWY_NAMESPACE::Rebind<uint32_t, D> du; + const V kSign = BitCast(d, Set(du, 0x80000000u)); + const V original_sign = And(x, kSign); + x = AndNot(kSign, x); // abs + // 4-over-4-degree rational polynomial approximation on x+x*x. This improves + // the maximum error by about 5x over a rational polynomial for x. + auto xpxx = MulAdd(x, x, x); + HWY_ALIGN constexpr float p[(4 + 1) * 4] = { + HWY_REP4(2.62975656e-04f), HWY_REP4(-6.23553089e-03f), + HWY_REP4(7.38602301e-01f), HWY_REP4(2.64553172e+00f), + HWY_REP4(5.50034862e-01f), + }; + HWY_ALIGN constexpr float q[(4 + 1) * 4] = { + HWY_REP4(4.21350107e+02f), HWY_REP4(-4.28736818e+02f), + HWY_REP4(1.74364667e+02f), HWY_REP4(-3.39078883e+01f), + HWY_REP4(2.67718770e+00f), + }; + auto magnitude = EvalRationalPolynomial(d, xpxx, p, q); + return Or( + AndNot(kSign, + Mul(magnitude, Set(d, display_scaling_factor_from_10000_nits_))), + original_sign); + } + + // Maximum error 7e-7. + template <class D, class V> + JXL_INLINE V EncodedFromDisplay(D d, V x) const { + const hwy::HWY_NAMESPACE::Rebind<uint32_t, D> du; + const V kSign = BitCast(d, Set(du, 0x80000000u)); + const V original_sign = And(x, kSign); + x = AndNot(kSign, x); // abs + // 4-over-4-degree rational polynomial approximation on x**0.25, with two + // different polynomials above and below 1e-4. + auto xto025 = + Sqrt(Sqrt(Mul(x, Set(d, display_scaling_factor_to_10000_nits_)))); + HWY_ALIGN constexpr float p[(4 + 1) * 4] = { + HWY_REP4(1.351392e-02f), HWY_REP4(-1.095778e+00f), + HWY_REP4(5.522776e+01f), HWY_REP4(1.492516e+02f), + HWY_REP4(4.838434e+01f), + }; + HWY_ALIGN constexpr float q[(4 + 1) * 4] = { + HWY_REP4(1.012416e+00f), HWY_REP4(2.016708e+01f), + HWY_REP4(9.263710e+01f), HWY_REP4(1.120607e+02f), + HWY_REP4(2.590418e+01f), + }; + + HWY_ALIGN constexpr float plo[(4 + 1) * 4] = { + HWY_REP4(9.863406e-06f), HWY_REP4(3.881234e-01f), + HWY_REP4(1.352821e+02f), HWY_REP4(6.889862e+04f), + HWY_REP4(-2.864824e+05f), + }; + HWY_ALIGN constexpr float qlo[(4 + 1) * 4] = { + HWY_REP4(3.371868e+01f), HWY_REP4(1.477719e+03f), + HWY_REP4(1.608477e+04f), HWY_REP4(-4.389884e+04f), + HWY_REP4(-2.072546e+05f), + }; + + auto magnitude = IfThenElse(Lt(x, Set(d, 1e-4f)), + EvalRationalPolynomial(d, xto025, plo, qlo), + EvalRationalPolynomial(d, xto025, p, q)); + return Or(AndNot(kSign, magnitude), original_sign); + } + + private: + const float display_scaling_factor_to_10000_nits_; + const float display_scaling_factor_from_10000_nits_; +}; + +// sRGB +class TF_SRGB { + public: + template <typename V> + JXL_INLINE V DisplayFromEncoded(V x) const { + const HWY_FULL(float) d; + const HWY_FULL(uint32_t) du; + const V kSign = BitCast(d, Set(du, 0x80000000u)); + const V original_sign = And(x, kSign); + x = AndNot(kSign, x); // abs + + // TODO(janwas): range reduction + // Computed via af_cheb_rational (k=100); replicated 4x. + HWY_ALIGN constexpr float p[(4 + 1) * 4] = { + 2.200248328e-04f, 2.200248328e-04f, 2.200248328e-04f, 2.200248328e-04f, + 1.043637593e-02f, 1.043637593e-02f, 1.043637593e-02f, 1.043637593e-02f, + 1.624820318e-01f, 1.624820318e-01f, 1.624820318e-01f, 1.624820318e-01f, + 7.961564959e-01f, 7.961564959e-01f, 7.961564959e-01f, 7.961564959e-01f, + 8.210152774e-01f, 8.210152774e-01f, 8.210152774e-01f, 8.210152774e-01f, + }; + HWY_ALIGN constexpr float q[(4 + 1) * 4] = { + 2.631846970e-01f, 2.631846970e-01f, 2.631846970e-01f, + 2.631846970e-01f, 1.076976492e+00f, 1.076976492e+00f, + 1.076976492e+00f, 1.076976492e+00f, 4.987528350e-01f, + 4.987528350e-01f, 4.987528350e-01f, 4.987528350e-01f, + -5.512498495e-02f, -5.512498495e-02f, -5.512498495e-02f, + -5.512498495e-02f, 6.521209011e-03f, 6.521209011e-03f, + 6.521209011e-03f, 6.521209011e-03f, + }; + const V linear = Mul(x, Set(d, kLowDivInv)); + const V poly = EvalRationalPolynomial(d, x, p, q); + const V magnitude = + IfThenElse(Gt(x, Set(d, kThreshSRGBToLinear)), poly, linear); + return Or(AndNot(kSign, magnitude), original_sign); + } + + // Error ~5e-07 + template <class D, class V> + JXL_INLINE V EncodedFromDisplay(D d, V x) const { + const hwy::HWY_NAMESPACE::Rebind<uint32_t, D> du; + const V kSign = BitCast(d, Set(du, 0x80000000u)); + const V original_sign = And(x, kSign); + x = AndNot(kSign, x); // abs + + // Computed via af_cheb_rational (k=100); replicated 4x. + HWY_ALIGN constexpr float p[(4 + 1) * 4] = { + -5.135152395e-04f, -5.135152395e-04f, -5.135152395e-04f, + -5.135152395e-04f, 5.287254571e-03f, 5.287254571e-03f, + 5.287254571e-03f, 5.287254571e-03f, 3.903842876e-01f, + 3.903842876e-01f, 3.903842876e-01f, 3.903842876e-01f, + 1.474205315e+00f, 1.474205315e+00f, 1.474205315e+00f, + 1.474205315e+00f, 7.352629620e-01f, 7.352629620e-01f, + 7.352629620e-01f, 7.352629620e-01f, + }; + HWY_ALIGN constexpr float q[(4 + 1) * 4] = { + 1.004519624e-02f, 1.004519624e-02f, 1.004519624e-02f, 1.004519624e-02f, + 3.036675394e-01f, 3.036675394e-01f, 3.036675394e-01f, 3.036675394e-01f, + 1.340816930e+00f, 1.340816930e+00f, 1.340816930e+00f, 1.340816930e+00f, + 9.258482155e-01f, 9.258482155e-01f, 9.258482155e-01f, 9.258482155e-01f, + 2.424867759e-02f, 2.424867759e-02f, 2.424867759e-02f, 2.424867759e-02f, + }; + const V linear = Mul(x, Set(d, kLowDiv)); + const V poly = EvalRationalPolynomial(d, Sqrt(x), p, q); + const V magnitude = + IfThenElse(Gt(x, Set(d, kThreshLinearToSRGB)), poly, linear); + return Or(AndNot(kSign, magnitude), original_sign); + } + + private: + static constexpr float kThreshSRGBToLinear = 0.04045f; + static constexpr float kThreshLinearToSRGB = 0.0031308f; + static constexpr float kLowDiv = 12.92f; + static constexpr float kLowDivInv = 1.0f / kLowDiv; +}; + +// Linear to sRGB conversion with error of at most 1.2e-4. +template <typename D, typename V> +V FastLinearToSRGB(D d, V v) { + const hwy::HWY_NAMESPACE::Rebind<uint32_t, D> du; + const hwy::HWY_NAMESPACE::Rebind<int32_t, D> di; + // Convert to 0.25 - 0.5 range. + auto v025_05 = BitCast( + d, And(Or(BitCast(du, v), Set(du, 0x3e800000)), Set(du, 0x3effffff))); + // third degree polynomial approximation between 0.25 and 0.5 + // of 1.055/2^(7/2.4) * x^(1/2.4) * 0.5. A degree 4 polynomial only improves + // accuracy by about 3x. + auto d1 = MulAdd(v025_05, Set(d, 0.059914046f), Set(d, -0.108894556f)); + auto d2 = MulAdd(d1, v025_05, Set(d, 0.107963754f)); + auto pow = MulAdd(d2, v025_05, Set(d, 0.018092343f)); + // Compute extra multiplier depending on exponent. Valid exponent range for + // [0.0031308f, 1.0) is 0...8 after subtracting 118. + // The next three constants contain a representation of the powers of + // 2**(1/2.4) = 2**(5/12) times two; in particular, bits from 26 to 31 are + // always the same and in k2to512powers_basebits, and the two arrays contain + // the next groups of 8 bits. This ends up being a 22-bit representation (with + // a mantissa of 13 bits). The choice of polynomial to approximate is such + // that the multiplication factor has the highest 5 bits constant, and that + // the factor for the lowest possible exponent is a power of two (thus making + // the additional bits 0, which is used to correctly merge back together the + // floats). + constexpr uint32_t k2to512powers_basebits = 0x40000000; + HWY_ALIGN constexpr uint8_t k2to512powers_25to18bits[16] = { + 0x0, 0xa, 0x19, 0x26, 0x32, 0x41, 0x4d, 0x5c, + 0x68, 0x75, 0x83, 0x8f, 0xa0, 0xaa, 0xb9, 0xc6, + }; + HWY_ALIGN constexpr uint8_t k2to512powers_17to10bits[16] = { + 0x0, 0xb7, 0x4, 0xd, 0xcb, 0xe7, 0x41, 0x68, + 0x51, 0xd1, 0xeb, 0xf2, 0x0, 0xb7, 0x4, 0xd, + }; + // Note that vld1q_s8_x2 on ARM seems to actually be slower. +#if HWY_TARGET != HWY_SCALAR + using hwy::HWY_NAMESPACE::ShiftLeft; + using hwy::HWY_NAMESPACE::ShiftRight; + // Every lane of exp is now (if cast to byte) {0, 0, 0, <index for lookup>}. + auto exp = Sub(ShiftRight<23>(BitCast(di, v)), Set(di, 118)); + auto pow25to18bits = TableLookupBytes( + LoadDup128(di, + reinterpret_cast<const int32_t*>(k2to512powers_25to18bits)), + exp); + auto pow17to10bits = TableLookupBytes( + LoadDup128(di, + reinterpret_cast<const int32_t*>(k2to512powers_17to10bits)), + exp); + // Now, pow* contain {0, 0, 0, <part of float repr of multiplier>}. Here + // we take advantage of the fact that each table has its position 0 equal to + // 0. + // We can now just reassemble the float. + auto mul = BitCast( + d, Or(Or(ShiftLeft<18>(pow25to18bits), ShiftLeft<10>(pow17to10bits)), + Set(di, k2to512powers_basebits))); +#else + // Fallback for scalar. + uint32_t exp = ((BitCast(di, v).raw >> 23) - 118) & 0xf; + auto mul = BitCast(d, Set(di, (k2to512powers_25to18bits[exp] << 18) | + (k2to512powers_17to10bits[exp] << 10) | + k2to512powers_basebits)); +#endif + return IfThenElse(Lt(v, Set(d, 0.0031308f)), Mul(v, Set(d, 12.92f)), + MulAdd(pow, mul, Set(d, -0.055))); +} + +// NOLINTNEXTLINE(google-readability-namespace-comments) +} // namespace HWY_NAMESPACE +} // namespace jxl +HWY_AFTER_NAMESPACE(); + +#endif // LIB_JXL_CMS_TRANSFER_FUNCTIONS_INL_H_ |