Removed KGuiAddons dependency

CMakeLists.txt

@@ -20,7 +20,6 @@ find_package(Qt${QT_VERSION_MAJOR} CONFIG REQUIRED Core LinguistTools Widgets)
 #
 # Other dependencies
 #
-find_package(KF${QT_VERSION_MAJOR}GuiAddons CONFIG REQUIRED)
 find_package(KF${QT_VERSION_MAJOR}WidgetsAddons CONFIG REQUIRED)
 find_package(ECM REQUIRED NO_MODULE)
 list(APPEND CMAKE_MODULE_PATH ${ECM_MODULE_PATH})
@@ -39,6 +38,7 @@ set(PROJECT_SOURCES
     src/componenteditor.cpp
     src/contrastpreview.h
     src/contrastpreview.cpp
+    src/hcycolorspace.h
     src/hsvcolorspace.h
     src/hsvcolorspace.cpp
     src/imagegradientselector.h
@@ -77,7 +77,6 @@ target_include_directories(${PROJECT_NAME} PRIVATE
 target_link_libraries(${PROJECT_NAME} PRIVATE
     Qt::Core
     Qt::Widgets
-    KF${QT_VERSION_MAJOR}::GuiAddons
     KF${QT_VERSION_MAJOR}::WidgetsAddons
 )
 if (UNIX AND NOT APPLE)

src/contrastpreview.cpp

@@ -1,6 +1,5 @@
 #include "contrastpreview.h"
-
-#include <KColorUtils>
+#include "hcycolorspace.h"
 
 #include <QLabel>
 #include <QLocale>
@@ -49,7 +48,14 @@ void ContrastPreview::updatePreview()
 
 void ContrastPreview::updateRatioLabel()
 {
-    qreal ratio = KColorUtils::contrastRatio(mBackgroundColor, mForegroundColor);
+    hcy::color_comp_t lumaBg = hcy::luminance(mBackgroundColor.redF(),
+                                              mBackgroundColor.greenF(),
+                                              mBackgroundColor.blueF());
+    hcy::color_comp_t lumaFg = hcy::luminance(mForegroundColor.redF(),
+                                              mForegroundColor.greenF(),
+                                              mForegroundColor.blueF());
+    qreal ratio = hcy::contrast_ratio(lumaBg, lumaFg);
+
     QString level;
     if (ratio < ACCEPTABLE_CONTRAST_RATIO) {
         level = tr("Bad");

src/hcycolorspace.h

@@ -0,0 +1,61 @@
+
+/*
+    SPDX-License-Identifier: CC0-1.0
+
+    You should have received a copy of the CC0 legalcode along with this work.
+    If not, see <http://creativecommons.org/publicdomain/zero/1.0/>.
+*/
+#include <QtGlobal>
+
+#include <algorithm>
+#include <array>
+
+#include <math.h>
+
+namespace hcy {
+
+#if QT_VERSION < 0x060000
+    typedef qreal color_comp_t; // double
+    static constexpr qreal color_comp_min { 0.0 };
+    static constexpr qreal color_comp_max { 1.0 };
+#else
+    typedef float color_comp_t;
+    static constexpr float color_comp_min { 0.0f };
+    static constexpr float color_comp_max { 1.0f };
+#endif
+
+#if 0
+// https://www.itu.int/dms_pubrec/itu-r/rec/bt/R-REC-BT.601-7-201103-I!!PDF-E.pdf
+// https://www.w3.org/TR/AERT/#color-contrast
+static constexpr std::array<color_comp_t, 3> ry = { 0.299, 0.587, 0.114 };
+#else
+// https://www.itu.int/dms_pubrec/itu-r/rec/bt/R-REC-BT.709-6-201506-I!!PDF-E.pdf
+// https://www.w3.org/WAI/GL/wiki/Relative_luminance#Definition_as_Stated_in_WCAG_2.x
+// https://en.wikipedia.org/wiki/Luma_(video)
+// https://en.wikipedia.org/wiki/Relative_luminance
+static constexpr std::array<color_comp_t, 3> ry = { 0.2126, 0.7152, 0.0722 };
+#endif
+
+// https://stackoverflow.com/questions/596216/formula-to-determine-perceived-brightness-of-rgb-color
+static constexpr color_comp_t relative_luminance(color_comp_t r, color_comp_t g, color_comp_t b)
+{
+    return ry[0] * r + ry[1] * g + ry[2] * b;
+}
+
+// https://www.w3.org/TR/WCAG/#dfn-contrast-ratio
+static constexpr color_comp_t contrast_ratio(color_comp_t a, color_comp_t b)
+{
+    return (a > b) ? (a + 0.05) / (b + 0.05) : (b + 0.05) / (a + 0.05);
+}
+
+static constexpr color_comp_t gamma_correction(color_comp_t color_component)
+{
+    color_comp_t color_comp = std::clamp(color_component, color_comp_min, color_comp_max);
+    return (color_comp <= 0.04045) ? (color_comp / 12.92) : std::pow((color_comp + 0.055) / 1.055, 2.4);
+}
+
+static const color_comp_t luminance(color_comp_t r, color_comp_t g, color_comp_t b)
+{
+    return relative_luminance(gamma_correction(r), gamma_correction(g), gamma_correction(b));
+}
+} // namespace hcy