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#3919 Implement a better threshold check for contrast colors

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Gaute Lindkvist 2018-12-21 08:50:47 +01:00
parent 6754f837d4
commit 68fb72311e
2 changed files with 60 additions and 18 deletions
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47
ApplicationCode/Application/Tools/RiaColorTools.cpp
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@ -1,5 +1,6 @@
///////////////////////////////////////////////////////////////////////////////// /////////////////////////////////////////////////////////////////////////////////
// //
// Copyright (C) 2018- Equinor ASA
// Copyright (C) 2017 Statoil ASA // Copyright (C) 2017 Statoil ASA
// //
// ResInsight is free software: you can redistribute it and/or modify // ResInsight is free software: you can redistribute it and/or modify
@ -21,11 +22,13 @@
#include <algorithm> #include <algorithm>
//-------------------------------------------------------------------------------------------------- //--------------------------------------------------------------------------------------------------
/// /// Uses W3.org relative luminance calculation taking into account the different luminance of the different colors
/// https://www.w3.org/TR/WCAG20-TECHS/G18.html
/// Luminance is between [0, 1] so anything above 0.5 is considered in the bright half of the spectrum.
//-------------------------------------------------------------------------------------------------- //--------------------------------------------------------------------------------------------------
bool RiaColorTools::isBrightnessAboveThreshold(cvf::Color3f backgroundColor) bool RiaColorTools::isBrightnessAboveThreshold(cvf::Color3f backgroundColor)
{ {
if (backgroundColor.r() + backgroundColor.g() + backgroundColor.b() > 1.5f) if (relativeLuminance(backgroundColor) > 0.5)
{ {
return true; return true;
} }
@ -55,9 +58,8 @@ cvf::Color3f RiaColorTools::computeOffsetColor(cvf::Color3f color, float offsetF
gridB = color.b() + (1.0f - color.b()) * offsetFactor; gridB = color.b() + (1.0f - color.b()) * offsetFactor;
} }
return cvf::Color3f(cvf::Math::clamp(gridR, 0.0f, 1.0f), return cvf::Color3f(
cvf::Math::clamp(gridG, 0.0f, 1.0f), cvf::Math::clamp(gridR, 0.0f, 1.0f), cvf::Math::clamp(gridG, 0.0f, 1.0f), cvf::Math::clamp(gridB, 0.0f, 1.0f));
cvf::Math::clamp(gridB, 0.0f, 1.0f));
} }
//-------------------------------------------------------------------------------------------------- //--------------------------------------------------------------------------------------------------
@ -106,3 +108,38 @@ QColor RiaColorTools::toQColor(cvf::Color4f color)
{ {
return toQColor(color.toColor3f(), color.a()); return toQColor(color.toColor3f(), color.a());
} }
//--------------------------------------------------------------------------------------------------
///
//--------------------------------------------------------------------------------------------------
float RiaColorTools::contrastRatio(cvf::Color3f color1, cvf::Color3f color2)
{
float L1 = relativeLuminance(color1);
float L2 = relativeLuminance(color2);
float Lmin = std::min(L1, L2);
float Lmax = std::max(L1, L2);
return (Lmax + 0.05) / (Lmin + 0.05);
}
//--------------------------------------------------------------------------------------------------
///
//--------------------------------------------------------------------------------------------------
float RiaColorTools::relativeLuminance(cvf::Color3f backgroundColor)
{
float R = calculateNonLinearColorValue(backgroundColor.r());
float G = calculateNonLinearColorValue(backgroundColor.g());
float B = calculateNonLinearColorValue(backgroundColor.b());
double luminance = 0.2126 * R + 0.7152 * G + 0.0722 * B;
return luminance;
}
//--------------------------------------------------------------------------------------------------
///
//--------------------------------------------------------------------------------------------------
float RiaColorTools::calculateNonLinearColorValue(float colorFraction)
{
return colorFraction <= 0.03928 ? colorFraction / 12.92 : std::pow((colorFraction + 0.055) / 1.055, 2.4);
}

5
ApplicationCode/Application/Tools/RiaColorTools.h
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@ -1,5 +1,6 @@
///////////////////////////////////////////////////////////////////////////////// /////////////////////////////////////////////////////////////////////////////////
// //
// Copyright (C) 2018- Equinor ASA
// Copyright (C) 2017 Statoil ASA // Copyright (C) 2017 Statoil ASA
// //
// ResInsight is free software: you can redistribute it and/or modify // ResInsight is free software: you can redistribute it and/or modify
@ -38,4 +39,8 @@ public:
static cvf::Color3f constrastColor(cvf::Color3f backgroundColor); static cvf::Color3f constrastColor(cvf::Color3f backgroundColor);
static QColor toQColor(cvf::Color3f color, float alpha = 1.0f); static QColor toQColor(cvf::Color3f color, float alpha = 1.0f);
static QColor toQColor(cvf::Color4f color); static QColor toQColor(cvf::Color4f color);
static float contrastRatio(cvf::Color3f color1, cvf::Color3f color2);
private:
static float relativeLuminance(cvf::Color3f backgroundColor);
static float calculateNonLinearColorValue(float colorFraction);
}; };