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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-28 14:29:10 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-28 14:29:10 +0000 |
commit | 2aa4a82499d4becd2284cdb482213d541b8804dd (patch) | |
tree | b80bf8bf13c3766139fbacc530efd0dd9d54394c /gfx/src/RelativeLuminanceUtils.h | |
parent | Initial commit. (diff) | |
download | firefox-2aa4a82499d4becd2284cdb482213d541b8804dd.tar.xz firefox-2aa4a82499d4becd2284cdb482213d541b8804dd.zip |
Adding upstream version 86.0.1.upstream/86.0.1upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'gfx/src/RelativeLuminanceUtils.h')
-rw-r--r-- | gfx/src/RelativeLuminanceUtils.h | 65 |
1 files changed, 65 insertions, 0 deletions
diff --git a/gfx/src/RelativeLuminanceUtils.h b/gfx/src/RelativeLuminanceUtils.h new file mode 100644 index 0000000000..64047a4e56 --- /dev/null +++ b/gfx/src/RelativeLuminanceUtils.h @@ -0,0 +1,65 @@ +/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ +/* vim: set ts=8 sts=2 et sw=2 tw=80: */ +/* This Source Code Form is subject to the terms of the Mozilla Public + * License, v. 2.0. If a copy of the MPL was not distributed with this + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ + +#ifndef mozilla_RelativeLuminanceUtils_h +#define mozilla_RelativeLuminanceUtils_h + +#include "nsColor.h" + +namespace mozilla { + +// Utilities for calculating relative luminance based on the algorithm +// defined in https://www.w3.org/TR/WCAG20/#relativeluminancedef +class RelativeLuminanceUtils { + public: + // Compute the relative luminance. + static float Compute(nscolor aColor) { + float r = ComputeComponent(NS_GET_R(aColor)); + float g = ComputeComponent(NS_GET_G(aColor)); + float b = ComputeComponent(NS_GET_B(aColor)); + return ComputeFromComponents(r, g, b); + } + + // Adjust the relative luminance of the given color. + static nscolor Adjust(nscolor aColor, float aLuminance) { + float r = ComputeComponent(NS_GET_R(aColor)); + float g = ComputeComponent(NS_GET_G(aColor)); + float b = ComputeComponent(NS_GET_B(aColor)); + float luminance = ComputeFromComponents(r, g, b); + float factor = aLuminance / luminance; + uint8_t r1 = DecomputeComponent(r * factor); + uint8_t g1 = DecomputeComponent(g * factor); + uint8_t b1 = DecomputeComponent(b * factor); + return NS_RGBA(r1, g1, b1, NS_GET_A(aColor)); + } + + private: + static float ComputeComponent(uint8_t aComponent) { + float v = float(aComponent) / 255.0f; + if (v <= 0.03928f) { + return v / 12.92f; + } + return std::pow((v + 0.055f) / 1.055f, 2.4f); + } + + static constexpr float ComputeFromComponents(float aR, float aG, float aB) { + return 0.2126f * aR + 0.7152f * aG + 0.0722f * aB; + } + + // Inverse function of ComputeComponent. + static uint8_t DecomputeComponent(float aComponent) { + if (aComponent <= 0.03928f / 12.92f) { + aComponent *= 12.92f; + } else { + aComponent = std::pow(aComponent, 1.0f / 2.4f) * 1.055f - 0.055f; + } + return ClampColor(aComponent * 255.0f); + } +}; + +} // namespace mozilla + +#endif // mozilla_RelativeLuminanceUtils_h |