paintarea.h Example File

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  #ifndef PAINTAREA_H
  #define PAINTAREA_H

  #include <QColor>
  #include <QImage>
  #include <QPainterPath>
  #include <QWidget>

  class BrushInterface;

  class PaintArea : public QWidget
  {
      Q_OBJECT

  public:
      PaintArea(QWidget *parent = nullptr);

      bool openImage(const QString &fileName);
      bool saveImage(const QString &fileName, const char *fileFormat);
      void setImage(const QImage &image);
      void insertShape(const QPainterPath &path);
      void setBrushColor(const QColor &color);
      void setBrushWidth(int width);
      void setBrush(BrushInterface *brushInterface, const QString &brush);

      QImage image() const { return theImage; }
      QColor brushColor() const { return color; }
      int brushWidth() const { return thickness; }
      QSize sizeHint() const override;

  protected:
      void paintEvent(QPaintEvent *event) override;
      void mousePressEvent(QMouseEvent *event) override;
      void mouseMoveEvent(QMouseEvent *event) override;
      void mouseReleaseEvent(QMouseEvent *event) override;

  private:
      void setupPainter(QPainter &painter);

      QImage theImage = {500, 400, QImage::Format_RGB32};
      QColor color = Qt::blue;
      int thickness = 3;

      BrushInterface *brushInterface = nullptr;
      QString brush;
      QPoint lastPos = {-1, -1};

      QPainterPath pendingPath;
  };

  #endif