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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 17:32:43 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 17:32:43 +0000 |
commit | 6bf0a5cb5034a7e684dcc3500e841785237ce2dd (patch) | |
tree | a68f146d7fa01f0134297619fbe7e33db084e0aa /third_party/jpeg-xl/lib/jxl/enc_photon_noise.cc | |
parent | Initial commit. (diff) | |
download | thunderbird-upstream.tar.xz thunderbird-upstream.zip |
Adding upstream version 1:115.7.0.upstream/1%115.7.0upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'third_party/jpeg-xl/lib/jxl/enc_photon_noise.cc')
-rw-r--r-- | third_party/jpeg-xl/lib/jxl/enc_photon_noise.cc | 89 |
1 files changed, 89 insertions, 0 deletions
diff --git a/third_party/jpeg-xl/lib/jxl/enc_photon_noise.cc b/third_party/jpeg-xl/lib/jxl/enc_photon_noise.cc new file mode 100644 index 0000000000..3786ef5cf5 --- /dev/null +++ b/third_party/jpeg-xl/lib/jxl/enc_photon_noise.cc @@ -0,0 +1,89 @@ +// 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. + +#include "lib/jxl/enc_photon_noise.h" + +namespace jxl { + +namespace { + +// Assumes a daylight-like spectrum. +// https://www.strollswithmydog.com/effective-quantum-efficiency-of-sensor/#:~:text=11%2C260%20photons/um%5E2/lx-s +constexpr float kPhotonsPerLxSPerUm2 = 11260; + +// Order of magnitude for cameras in the 2010-2020 decade, taking the CFA into +// account. +constexpr float kEffectiveQuantumEfficiency = 0.20; + +// TODO(sboukortt): reevaluate whether these are good defaults, notably whether +// it would be worth making read noise higher at lower ISO settings. +constexpr float kPhotoResponseNonUniformity = 0.005; +constexpr float kInputReferredReadNoise = 3; + +// Assumes a 35mm sensor. +constexpr float kSensorAreaUm2 = 36000.f * 24000; + +template <typename T> +inline constexpr T Square(const T x) { + return x * x; +} +template <typename T> +inline constexpr T Cube(const T x) { + return x * x * x; +} + +} // namespace + +NoiseParams SimulatePhotonNoise(const size_t xsize, const size_t ysize, + const float iso) { + const float kOpsinAbsorbanceBiasCbrt = std::cbrt(kOpsinAbsorbanceBias[1]); + + // Focal plane exposure for 18% of kDefaultIntensityTarget, in lx·s. + // (ISO = 10 lx·s ÷ H) + const float h_18 = 10 / iso; + + const float pixel_area_um2 = kSensorAreaUm2 / (xsize * ysize); + + const float electrons_per_pixel_18 = kEffectiveQuantumEfficiency * + kPhotonsPerLxSPerUm2 * h_18 * + pixel_area_um2; + + NoiseParams params; + + for (size_t i = 0; i < NoiseParams::kNumNoisePoints; ++i) { + const float scaled_index = i / (NoiseParams::kNumNoisePoints - 2.f); + // scaled_index is used for XYB = (0, 2·scaled_index, 2·scaled_index) + const float y = 2 * scaled_index; + // 1 = default intensity target + const float linear = std::max( + 0.f, Cube(y - kOpsinAbsorbanceBiasCbrt) + kOpsinAbsorbanceBias[1]); + const float electrons_per_pixel = electrons_per_pixel_18 * (linear / 0.18f); + // Quadrature sum of read noise, photon shot noise (sqrt(S) so simply not + // squared here) and photo response non-uniformity. + // https://doi.org/10.1117/3.725073 + // Units are electrons rms. + const float noise = + std::sqrt(Square(kInputReferredReadNoise) + electrons_per_pixel + + Square(kPhotoResponseNonUniformity * electrons_per_pixel)); + const float linear_noise = noise * (0.18f / electrons_per_pixel_18); + const float opsin_derivative = + (1.f / 3) / Square(std::cbrt(linear - kOpsinAbsorbanceBias[1])); + const float opsin_noise = linear_noise * opsin_derivative; + + // TODO(sboukortt): verify more thoroughly whether the denominator is + // correct. + params.lut[i] = + Clamp1(opsin_noise / + (0.22f // norm_const + * std::sqrt(2.f) // red_noise + green_noise + * 1.13f // standard deviation of a plane of generated noise + ), + 0.f, 1.f); + } + + return params; +} + +} // namespace jxl |