Issue #118: First part of splitting

Pdf4QtLibCore/sources/pdfimageconversion.h

@@ -0,0 +1,97 @@
+//    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/>.
+
+#ifndef PDFIMAGECONVERSION_H
+#define PDFIMAGECONVERSION_H
+
+#include "pdfglobal.h"
+
+#include <QImage>
+
+namespace pdf
+{
+
+/// This class facilitates various image conversions,
+/// including transforming colored images into monochromatic (or bitonal) formats.
+class PDF4QTLIBSHARED_EXPORT PDFImageConversion
+{
+public:
+    PDFImageConversion();
+
+    enum class ConversionMethod
+    {
+        Automatic,  ///< The threshold is determined automatically using an algorithm.
+        Manual      ///< The threshold is manually provided by the user.
+    };
+
+    /// Sets the image to be converted using the specified conversion method.
+    /// This operation resets any previously converted image and the automatic threshold,
+    /// thereby erasing all prior image data.
+    /// \param image The image to be set for conversion.
+    void setImage(QImage image);
+
+    /// Sets the method for image conversion. Multiple methods are available
+    /// for selection. If the manual method is chosen, an appropriate threshold
+    /// must also be set by the user.
+    /// \param method The conversion method to be used.
+    void setConversionMethod(ConversionMethod method);
+
+    /// Sets the manual threshold value. When a non-manual (e.g., automatic) conversion
+    /// method is in use, this function will retain the manual threshold settings,
+    /// but the conversion will utilize an automatically calculated threshold for the image.
+    /// The manually set threshold is preserved and not overwritten. Therefore, if the
+    /// manual conversion method is later selected, the previously established manual
+    /// threshold will be applied.
+    /// \param threshold The manual threshold value to be set.
+    void setThreshold(int threshold);
+
+    /// This method converts the image into a bitonal (monochromatic) format. If
+    /// the automatic threshold calculation is enabled, it executes Otsu's 1D algorithm
+    /// to determine the threshold. When the manual conversion method is selected,
+    /// the automatic threshold calculation is bypassed, and the predefined manual threshold
+    /// value is utilized instead. This method returns true if the conversion is
+    /// successful, and false otherwise.
+    bool convert();
+
+    /// Returns the threshold used in image conversion. If the automatic conversion method is
+    /// selected, this function should be called only after executing the convert() method;
+    /// otherwise, it may return invalid data. The automatic threshold calculation is
+    /// performed within the convert() method.
+    /// \returns The threshold value used in image conversion.
+    int getThreshold() const;
+
+    /// Returns the converted image. This method should only be called after
+    /// the convert() method has been executed, and additionally, only if the
+    /// convert() method returns true. If these conditions are not met, the result
+    /// is undefined.
+    QImage getConvertedImage() const;
+
+private:
+    int calculateOtsu1DThreshold() const;
+
+    static constexpr int DEFAULT_THRESHOLD = 128;
+
+    QImage m_image;
+    QImage m_convertedImage;
+    ConversionMethod m_conversionMethod = ConversionMethod::Automatic;
+    int m_automaticThreshold = DEFAULT_THRESHOLD;
+    int m_manualThreshold = DEFAULT_THRESHOLD;
+};
+
+}   // namespace pdf
+
+#endif // PDFIMAGECONVERSION_H