implemented contrast slider

image_redactor/imageredactor.h

@@ -12,6 +12,7 @@ class ImageRedactor : public QGraphicsView
     Q_OBJECT
 public:
     ImageRedactor(QWidget *parent = nullptr);
+    QGraphicsScene *scene;
 protected:
     void wheelEvent(QWheelEvent *event);
 
@@ -20,7 +21,6 @@ protected:
     void mouseReleaseEvent(QMouseEvent *event);
 
 private:
-    QGraphicsScene *scene;
     QGraphicsPixmapItem *item;
 };