jfjoch_viewer: Improve in displaying overlay numbers

viewer/image_viewer/JFJochImage.cpp

@@ -680,6 +680,10 @@ void JFJochImage::writePixelLabels() {
     const int visH = std::max(0, endY - startY);
     int maxLabels = 1000;
 
+    // Choose thresholds that fit your UI width
+    constexpr float kMinFixed = 1e-3;
+    constexpr float kMaxFixed = 1e5;
+
     if (visW * visH  <= maxLabels) {
         QString numBuf; // reused buffer
 
@@ -688,14 +692,27 @@ void JFJochImage::writePixelLabels() {
                 const int idx = y * W + x;
                 const float val = image_fp[idx];
 
+                const auto absVal = std::abs(val);
+                const auto nearest = std::nearbyint(val);
+
                 const QString* pText = nullptr;
                 if (std::isnan(val)) {
                     pText = &kGap;
                 } else if (std::isinf(val)) {
                     pText = std::signbit(val) ? &kErr : &kSat;
+                } else if (val == 0.0f) {
+                    numBuf = QStringLiteral("0");
+                    pText = &numBuf;
+                } else if (absVal >= kMinFixed && absVal < kMaxFixed) {
+                    if (std::abs(val - nearest) < 1e-6)
+                        numBuf = QString::number(static_cast<qint64>(val));
+                    else if (absVal < 1e4)
+                        numBuf = QString::number(val, 'f', 3);
+                    else
+                        numBuf = QString::number(val, 'f', 2);
+                    pText = &numBuf;
                 } else {
-                    // Fixed format reduces overhead and string length variability
-                    numBuf = QString::number(val, 'g', 4);
+                    numBuf = QString::number(val, 'e', 1);
                     pText = &numBuf;
                 }