Issue #108: Add accessibility options in pdf reader

Pdf4QtLib/sources/pdfcolorconvertor.cpp

@@ -0,0 +1,210 @@
+//    Copyright (C) 2023 Jakub Melka
+//
+//    This file is part of PDF4QT.
+//
+//    PDF4QT is free software: you can redistribute it and/or modify
+//    it under the terms of the GNU Lesser General Public License as published by
+//    the Free Software Foundation, either version 3 of the License, or
+//    with the written consent of the copyright owner, any later version.
+//
+//    PDF4QT is distributed in the hope that it will be useful,
+//    but WITHOUT ANY WARRANTY; without even the implied warranty of
+//    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+//    GNU Lesser General Public License for more details.
+//
+//    You should have received a copy of the GNU Lesser General Public License
+//    along with PDF4QT.  If not, see <https://www.gnu.org/licenses/>.
+
+#include "pdfcolorconvertor.h"
+#include "pdfimageconversion.h"
+#include "pdfutils.h"
+
+namespace pdf
+{
+
+PDFColorConvertor::PDFColorConvertor()
+{
+    calculateSigmoidParams();
+}
+
+bool PDFColorConvertor::isActive() const
+{
+    return m_mode != Mode::Normal;
+}
+
+void PDFColorConvertor::setMode(Mode mode)
+{
+    m_mode = mode;
+}
+
+QColor PDFColorConvertor::convert(QColor color, bool background, bool foreground) const
+{
+    switch (m_mode)
+    {
+        case Mode::Normal:
+            return color;
+
+        case Mode::InvertedColors:
+            return invertColor(color);
+
+        case Mode::Grayscale:
+        {
+            int gray = qGray(color.red(), color.green(), color.blue());
+            return QColor(gray, gray, gray, color.alpha());
+        }
+
+        case Mode::HighContrast:
+        {
+            const float lightness = color.lightnessF();
+            const float adjustedLightness = correctLigthnessBySigmoidFunction(lightness);
+            QColor hslColor = color.toHsl();
+            hslColor.setHslF(hslColor.hueF(), hslColor.saturationF(), adjustedLightness, color.alphaF());
+            return hslColor.toRgb();
+        }
+
+        case Mode::Bitonal:
+        {
+            const int lightness = color.lightness();
+            QColor bitonalColor = (lightness >= m_bitonalThreshold) ? QColor(Qt::white) : QColor(Qt::black);
+            bitonalColor.setAlpha(bitonalColor.alpha());
+            return bitonalColor;
+        }
+
+        case Mode::CustomColors:
+        {
+            if (background)
+            {
+                return m_backgroundColor;
+            }
+
+            if (foreground)
+            {
+                return m_foregroundColor;
+            }
+
+            const float lightness = color.lightnessF();
+            QColor hslColor = m_foregroundColor;
+            hslColor.setHslF(hslColor.hueF(), hslColor.saturationF(), lightness, color.alphaF());
+            return hslColor.toRgb();
+        }
+
+        default:
+            Q_ASSERT(false);
+            break;
+    }
+
+    return color;
+}
+
+QImage PDFColorConvertor::convert(QImage image) const
+{
+    switch (m_mode)
+    {
+        case Mode::Normal:
+            return image;
+
+        case Mode::InvertedColors:
+        {
+            image.invertPixels(QImage::InvertRgb);
+            return image;
+        }
+
+        case Mode::Grayscale:
+        {
+            QImage alpha = image.convertedTo(QImage::Format_Alpha8);
+            QImage grayscaleImage = image.convertedTo(QImage::Format_Grayscale8);
+            QImage resultImage = grayscaleImage;
+            resultImage = resultImage.convertedTo(QImage::Format_ARGB32);
+            resultImage.setAlphaChannel(std::move(alpha));
+            return resultImage;
+        }
+
+        case Mode::Bitonal:
+        {
+            PDFImageConversion imageConversion;
+            imageConversion.setConversionMethod(PDFImageConversion::ConversionMethod::Automatic);
+            imageConversion.setImage(image);
+
+            if (imageConversion.convert())
+            {
+                return imageConversion.getConvertedImage();
+            }
+
+            return image;
+        }
+
+        case Mode::HighContrast:
+        case Mode::CustomColors:
+        {
+            for (int row = 0; row < image.height(); ++row)
+            {
+                for (int column = 0; column < image.width(); ++column)
+                {
+                    QColor color = image.pixelColor(column, row);
+                    QColor adjustedColor = convert(color, false, false);
+                    image.setPixelColor(column, row, adjustedColor);
+                }
+            }
+
+            return image;
+        }
+
+        default:
+            Q_ASSERT(false);
+            break;
+    }
+
+    return image;
+}
+
+void PDFColorConvertor::setHighContrastBrightnessFactor(float factor)
+{
+    m_sigmoidParamC = factor;
+    calculateSigmoidParams();
+}
+
+float PDFColorConvertor::correctLigthnessBySigmoidFunction(float lightness) const
+{
+    const float adjustedLightness = sigmoidFunction(lightness);
+    const float normalizedLightness = (adjustedLightness - m_sigmoidParamC_Black) / m_sigmoidParamC_Range;
+    return qBound(0.0f, normalizedLightness, 1.0f);
+}
+
+float PDFColorConvertor::sigmoidFunction(float value) const
+{
+    return 1.0f / (1.0f + std::expf(-m_sigmoidParamC * (value - 0.5f)));
+}
+
+float PDFColorConvertor::sigmoidParamC_Black() const
+{
+    return sigmoidFunction(0.0);
+}
+
+float PDFColorConvertor::sigmoidParamC_White() const
+{
+    return sigmoidFunction(1.0);
+}
+
+float PDFColorConvertor::sigmoidParamC_Range() const
+{
+    return sigmoidParamC_White() - sigmoidParamC_Black();
+}
+
+void PDFColorConvertor::calculateSigmoidParams()
+{
+    m_sigmoidParamC_Black = sigmoidParamC_Black();
+    m_sigmoidParamC_White = sigmoidParamC_White();
+    m_sigmoidParamC_Range = sigmoidParamC_Range();
+}
+
+int PDFColorConvertor::getBitonalThreshold() const
+{
+    return m_bitonalThreshold;
+}
+
+void PDFColorConvertor::setBitonalThreshold(int newBitonalThreshold)
+{
+    m_bitonalThreshold = newBitonalThreshold;
+}
+
+}   // namespace pdf