Reorganize codes

Reorganize all parts of codes;
Fix a bug that index page color is not correct when initialized.

src/big_image.h

@@ -1,25 +1,27 @@
 #ifndef BIG_IMAGE_H
 #define BIG_IMAGE_H
 
-#include <QWidget>
-#include <DBlurEffectWidget>
 #include <QMouseEvent>
 #include <QLabel>
+
+#include <DBlurEffectWidget>
+
 DWIDGET_USE_NAMESPACE
 
 class big_image : public DBlurEffectWidget
 {
     Q_OBJECT
+
 public:
     explicit big_image(DBlurEffectWidget *parent = nullptr);
-    void mousePressEvent(QMouseEvent *event);
-    QLabel *m_image=new QLabel;
+
+    QLabel *m_image;
+
     void setimage(QPixmap);
-    void focusOutEvent(QFocusEvent *event);
 
-signals:
-
-public slots:
+protected:
+    void mousePressEvent(QMouseEvent *event) override;
+    void focusOutEvent(QFocusEvent *event) override;
 };
 
 #endif // BIG_IMAGE_H