diff --git a/preview/PreviewImage.cpp b/preview/PreviewImage.cpp
index daef6864..b3841962 100644
--- a/preview/PreviewImage.cpp
+++ b/preview/PreviewImage.cpp
@@ -46,7 +46,6 @@ void PreviewImage::spot(std::vector<rgb> &ret, int64_t in_xpixel, int64_t in_ypi
 void PreviewImage::roi(std::vector<rgb> &ret, int64_t in_xpixel, int64_t in_ypixel, int64_t roi_number) const {
     color_pixel(ret, in_xpixel, in_ypixel, plotly[roi_number % 10]);
 }
-
 template<class T>
 std::vector<rgb> PreviewImage::GenerateRGB(const uint8_t *value_8,
                                            int64_t special_value_64,
@@ -87,16 +86,32 @@ std::vector<rgb> PreviewImage::GenerateRGB(const uint8_t *value_8,
 
     }
 
+    // LUT-based mapping (fast path)
+    const auto &lut = scale.LUTData();
+    const int64_t lut_size = static_cast<int64_t>(lut.size());
+    const float lut_scale = static_cast<float>(lut_size - 1);
+    const float inv_range = (foreground > background)
+        ? (lut_scale / (foreground - background))
+        : 0.0f;
+
+    const rgb gap_color = scale.Apply(ColorScaleSpecial::Gap);
+    const rgb bad_color = scale.Apply(ColorScaleSpecial::BadPixel);
+
     std::vector<rgb> ret(xpixel * ypixel);
-    for (int i = 0; i < xpixel*ypixel; i++) {
-        if (mask[i] == MaskGap)
-            ret[i] = scale.Apply(ColorScaleSpecial::Gap);
-        else if ((value[i] == special_value)
-                 || (mask[i] == MaskDet)
-                 || (settings.show_user_mask && (mask[i] == MaskUsr))) {
-            ret[i] = scale.Apply(ColorScaleSpecial::BadPixel);
-        } else
-            ret[i] = scale.Apply(value[i], background, foreground);
+    for (int i = 0; i < xpixel * ypixel; i++) {
+        if (mask[i] == MaskGap) {
+            ret[i] = gap_color;
+        } else if ((value[i] == special_value)
+                   || (mask[i] == MaskDet)
+                   || (settings.show_user_mask && (mask[i] == MaskUsr))) {
+            ret[i] = bad_color;
+        } else {
+            const float v = static_cast<float>(value[i]);
+            int64_t idx = static_cast<int64_t>((v - background) * inv_range + 0.5f);
+            if (idx < 0) idx = 0;
+            else if (idx >= lut_size) idx = lut_size - 1;
+            ret[i] = lut[idx];
+        }
     }
     return ret;
 }