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 --- gfx/src/RelativeLuminanceUtils.h | 78 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 78 insertions(+) create mode 100644 gfx/src/RelativeLuminanceUtils.h (limited to 'gfx/src/RelativeLuminanceUtils.h') diff --git a/gfx/src/RelativeLuminanceUtils.h b/gfx/src/RelativeLuminanceUtils.h new file mode 100644 index 0000000000..34e3ccf6da --- /dev/null +++ b/gfx/src/RelativeLuminanceUtils.h @@ -0,0 +1,78 @@ +/* -*- 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 + 0.05f) / (luminance + 0.05f); + uint8_t r1 = + DecomputeComponent(std::max(0.0f, (r + 0.05f) * factor - 0.05f)); + uint8_t g1 = + DecomputeComponent(std::max(0.0f, (g + 0.05f) * factor - 0.05f)); + uint8_t b1 = + DecomputeComponent(std::max(0.0f, (b + 0.05f) * factor - 0.05f)); + return NS_RGBA(r1, g1, b1, NS_GET_A(aColor)); + } + + // https://www.w3.org/TR/WCAG21/#dfn-contrast-ratio + static float ContrastRatio(nscolor aColor1, nscolor aColor2) { + float l1 = Compute(aColor1); + float l2 = Compute(aColor2); + if (l1 < l2) { + std::swap(l1, l2); + } + return (l1 + 0.05f) / (l2 + 0.05f); + } + + 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 -- cgit v1.2.3