Prepare for three channels STF

stretchtoolbar.h

@@ -2,15 +2,28 @@
 #define STRETCHTOOLBAR_H
 
 #include <QToolBar>
+#include <QStackedWidget>
 #include "stfslider.h"
 
 class Image;
 
+struct MTFParam
+{
+    float blackPoint[3] = {0.0f, 0.0f, 0.0f};
+    float midPoint[3] = {0.5f, 0.5f, 0.5f};
+    float whitePoint[3] = {1.0f, 1.0f, 1.0f};
+};
+
 class StretchToolbar : public QToolBar
 {
     Q_OBJECT
     STFSlider *m_stfSlider;
+    STFSlider *m_stfSliderR;
+    STFSlider *m_stfSliderG;
+    STFSlider *m_stfSliderB;
     QAction *m_autoStretchOnLoad;
+    QStackedWidget *m_stack;
+    MTFParam m_mtfParam;
 public:
     explicit StretchToolbar(QWidget *parent = nullptr);
 public slots:
@@ -18,7 +31,7 @@ public slots:
     void resetMTF();
     void imageLoaded(Image *img);
 signals:
-    void paramChanged(float low, float mid, float high);
+    void paramChanged(const MTFParam &params);
     void autoStretch();
     void invert(bool enable);
     void superPixel(bool enable);