viewer/widgets/JFJochSimpleImageViewer.cpp

@@ -36,6 +36,11 @@ JFJochSimpleImageViewer::JFJochSimpleImageViewer(QWidget *parent)
 
     // Keep overlays in pixel units independent of zoom (for labels font sizing)
     setViewportUpdateMode(QGraphicsView::FullViewportUpdate);
+
+    // QTimer for smoother movement/updates
+    repaint_timer_.setInterval(16); // ~60 FPS
+    repaint_timer_.setSingleShot(false);
+    connect(&repaint_timer_, &QTimer::timeout, this, &JFJochSimpleImageViewer::onRepaintTimer);
 }
 
 void JFJochSimpleImageViewer::clear() {
@@ -463,7 +468,7 @@ void JFJochSimpleImageViewer::updateROI() {
         roi_box_ = roi_box_.intersected(bounds);
     }
 
-    updateScene();
+   scheduleSceneUpdate();
 }
 
 void JFJochSimpleImageViewer::drawROI(QGraphicsScene* scn) {
@@ -534,8 +539,9 @@ JFJochSimpleImageViewer::computeROIStats(const QRect& roi_px) const {
     const int y1 = std::clamp(roi_px.bottom(), 0, std::max(0, H - 1));
     if (x1 < x0 || y1 < y0) return s;
 
-    // First pass: min, max, sum
-    double sum = 0.0L;
+    // One pass: min, max, sum, sum of squares
+    double sum = 0.0;
+    double sumsq = 0.0;
     s.min = std::numeric_limits<double>::infinity();
     s.max = -std::numeric_limits<double>::infinity();
     s.count = 0;
@@ -549,27 +555,48 @@ JFJochSimpleImageViewer::computeROIStats(const QRect& roi_px) const {
             if (v < s.min) s.min = v;
             if (v > s.max) s.max = v;
             sum += v;
+            sumsq += v * v;
             ++s.count;
         }
     }
 
     if (!s.valid()) return s;
 
-    s.avg = double(sum / s.count);
-
-    // Second pass: variance
-    double var_sum = 0.0L;
-    for (int y = y0; y <= y1; ++y) {
-        const size_t base = size_t(y) * size_t(W);
-        for (int x = x0; x <= x1; ++x) {
-            const size_t idx = base + size_t(x);
-            const double v = image_values_[idx];
-            if (std::isnan(v)) continue;
-            const double d = v - s.avg;
-            var_sum += d * d;
-        }
-    }
-    const double variance = (s.count > 1) ? (var_sum / s.count) : 0.0L;
-    s.stddev = std::sqrt(double(variance));
+    s.avg = sum / double(s.count);
+    double variance = sumsq / double(s.count) - s.avg * s.avg;
+    if (variance < 0.0) variance = 0.0; // guard small negatives from FP error
+    s.stddev = std::sqrt(variance);
     return s;
 }
+
+
+void JFJochSimpleImageViewer::onRepaintTimer() {
+    // Apply any pending pan
+    if (!qFuzzyIsNull(pan_accum_.x()) || !qFuzzyIsNull(pan_accum_.y())) {
+        translate(pan_accum_.x(), pan_accum_.y());
+        pan_accum_ = QPointF(0.0, 0.0);
+    }
+
+    // Rebuild scene if requested
+    if (needs_scene_update_) {
+        updateScene();
+        needs_scene_update_ = false;
+    }
+
+    // Stop timer if nothing pending
+    if (qFuzzyIsNull(pan_accum_.x()) && qFuzzyIsNull(pan_accum_.y()) && !needs_scene_update_) {
+        repaint_timer_.stop();
+    }
+}
+
+void JFJochSimpleImageViewer::schedulePanDelta(const QPointF& d) {
+    pan_accum_ += d;
+    if (!repaint_timer_.isActive())
+        repaint_timer_.start();
+}
+
+void JFJochSimpleImageViewer::scheduleSceneUpdate() {
+    needs_scene_update_ = true;
+    if (!repaint_timer_.isActive())
+        repaint_timer_.start();
+}

viewer/widgets/JFJochSimpleImageViewer.h

@@ -9,6 +9,7 @@
 #include <QPointF>
 #include <QGraphicsTextItem>
 #include <vector>
+#include <QTimer>
 
 #include "../SimpleImage.h"
 #include "../../common/ColorScale.h"
@@ -70,6 +71,14 @@ private:
     QPoint last_mouse_pos_;
     bool panning_ = false;
 
+    // Smooth movement/repaint
+    QTimer repaint_timer_;
+    QPointF pan_accum_{0.0, 0.0};
+    bool needs_scene_update_ = false;
+    void schedulePanDelta(const QPointF& d);
+    void scheduleSceneUpdate();
+    void onRepaintTimer();
+
     // Settings
     float background_ = 0.0f;
     float foreground_ = 10.0f;