feat(iv): area probe (#4767)

Fixes #4714 

This PR adds support for selecting a rectangular region within an image
to compute and display per-channel minimum, maximum, and average values.

The feature can be activated through the Tools menu or by using a
keyboard shortcut (Ctrl-A / Cmd-A) . Once active, the user can click and
drag with the left mouse button to define a rectangular area, which is
visually indicated by a blue outline. Upon releasing the mouse button,
the tool calculates statistics for all pixels within the selected area
and displays the results in the status bar.

---------

Signed-off-by: Danielle Imogu <dannieim689@gmail.com>

Author: dann1m

src/iv/imageviewer.cpp

@@ -491,6 +491,12 @@ ImageViewer::createActions()
     slideShowDuration->setAccelerated(true);
     connect(slideShowDuration, SIGNAL(valueChanged(int)), this,
             SLOT(setSlideShowDuration(int)));
+
+    toggleAreaSampleAct = new QAction(tr("&Toggle Area Sample"), this);
+    toggleAreaSampleAct->setCheckable(true);
+    toggleAreaSampleAct->setShortcut(tr("Ctrl+A"));
+    connect(toggleAreaSampleAct, SIGNAL(triggered()), this,
+            SLOT(toggleAreaSample()));
 }
 
 
@@ -737,6 +743,7 @@ ImageViewer::createMenus()
     // Mode: select, zoom, pan, wipe
     toolsMenu->addAction(showInfoWindowAct);
     toolsMenu->addAction(showPixelviewWindowAct);
+    toolsMenu->addAction(toggleAreaSampleAct);
     toolsMenu->addMenu(slideMenu);
     toolsMenu->addMenu(sortMenu);
 
@@ -2387,3 +2394,28 @@ ImageViewer::editPreferences()
     }
     preferenceWindow->show();
 }
+
+
+
+void
+ImageViewer::toggleAreaSample()
+{
+    m_areaSampleMode = !m_areaSampleMode;
+    if (m_areaSampleMode) {
+        setCursor(Qt::CrossCursor);
+    } else {
+        unsetCursor();
+    }
+    // if (m_areaSampleMode == false){
+    //     updateStatusBar();
+    // }
+    ((QOpenGLWidget*)(glwin))->update();
+}
+
+
+
+bool
+ImageViewer::areaSampleMode() const
+{
+    return m_areaSampleMode;
+}

src/iv/imageviewer.h

@@ -224,6 +224,11 @@ class ImageViewer final : public QMainWindow {
         return showPixelviewWindowAct && showPixelviewWindowAct->isChecked();
     }
 
+    bool probeviewOn(void) const
+    {
+        return toggleAreaSampleAct && toggleAreaSampleAct->isChecked();
+    }
+
     bool windowguidesOn(void) const
     {
         return toggleWindowGuidesAct && toggleWindowGuidesAct->isChecked();
@@ -249,6 +254,7 @@ class ImageViewer final : public QMainWindow {
 
     void rawcolor(bool val) { m_rawcolor = val; }
     bool rawcolor() const { return m_rawcolor; }
+    bool areaSampleMode() const;
 
     bool useOCIO() { return m_useOCIO; }
     const std::string& ocioColorSpace() { return m_ocioColourSpace; }
@@ -316,6 +322,7 @@ private slots:
     void showInfoWindow();       ///< View extended info on image
     void showPixelviewWindow();  ///< View closeup pixel view
     void editPreferences();      ///< Edit viewer preferences
+    void toggleAreaSample();     ///< Use area probe
 
     void useOCIOAction(bool checked);
     void ocioColorSpaceAction();
@@ -385,6 +392,7 @@ private slots:
     QAction* showInfoWindowAct;
     QAction* editPreferencesAct;
     QAction* showPixelviewWindowAct;
+    QAction* toggleAreaSampleAct;
     QAction* toggleWindowGuidesAct;
     QMenu *fileMenu, *editMenu, /**imageMenu,*/ *viewMenu, *toolsMenu,
         *helpMenu;
@@ -420,7 +428,8 @@ private slots:
     float m_default_gamma;                    // Default gamma of the display
     QPalette m_palette;                       // Custom palette
     bool m_darkPalette;                       // Use dark palette?
-    bool m_rawcolor = false;                  // Use raw color mode
+    bool m_rawcolor       = false;            // Use raw color mode
+    bool m_areaSampleMode = false;            // Use area sample mode
 
     // The default width and height of the window:
     static const int m_default_width  = 640;