diff --git a/rtengine/iimage.h b/rtengine/iimage.h
index 2eded8208..4362f369a 100644
--- a/rtengine/iimage.h
+++ b/rtengine/iimage.h
@@ -103,27 +103,27 @@ public:
 template<>
 inline void ImageDatas::convertTo(unsigned short src, unsigned char& dst) const
 {
-    dst = src / 257;
+    dst = (src + 128) / 257;
 }
 template<>
 inline void ImageDatas::convertTo(unsigned char src, int& dst) const
 {
-    dst = static_cast<int>(src) * 257;
+    dst = src * 257;
 }
 template<>
 inline void ImageDatas::convertTo(unsigned char src, unsigned short& dst) const
 {
-    dst = static_cast<unsigned short>(src) * 257;
+    dst = src * 257;
 }
 template<>
 inline void ImageDatas::convertTo(float src, unsigned char& dst) const
 {
-    dst = static_cast<unsigned short>(src) / 257;
+    dst = (static_cast<int>(src) + 128) / 257;
 }
 template<>
 inline void ImageDatas::convertTo(unsigned char src, float& dst) const
 {
-    dst = static_cast<unsigned short>(src) * 257;
+    dst = src * 257;
 }
 
 // --------------------------------------------------------------------
diff --git a/rtengine/image16.cc b/rtengine/image16.cc
index 9d41f96c5..11a05902f 100644
--- a/rtengine/image16.cc
+++ b/rtengine/image16.cc
@@ -28,9 +28,9 @@ namespace
 void getScanline8 (const uint16_t *red, const uint16_t *green, const uint16_t *blue, int width, unsigned char* buffer)
 {
     for (int i = 0, ix = 0; i < width; i++) {
-        buffer[ix++] = red[i] / 257;
-        buffer[ix++] = green[i] / 257;
-        buffer[ix++] = blue[i] / 257;
+        buffer[ix++] = (red[i] + 128) / 257;
+        buffer[ix++] = (green[i] + 128) / 257;
+        buffer[ix++] = (blue[i] + 128) / 257;
     }
 }
 
@@ -300,9 +300,9 @@ Image16::to8()
 
     for (int h = 0; h < height; ++h) {
         for (int w = 0; w < width; ++w) {
-            img8->r(h, w) = r(h, w) / 257;
-            img8->g(h, w) = g(h, w) / 257;
-            img8->b(h, w) = b(h, w) / 257;
+            img8->r(h, w) = (r(h, w) + 128) / 257;
+            img8->g(h, w) = (g(h, w) + 128) / 257;
+            img8->b(h, w) = (b(h, w) + 128) / 257;
         }
     }
 
diff --git a/rtengine/image8.cc b/rtengine/image8.cc
index 1cc648eb5..41589993d 100644
--- a/rtengine/image8.cc
+++ b/rtengine/image8.cc
@@ -74,7 +74,7 @@ void Image8::setScanline (int row, unsigned char* buffer, int bps, float *minVal
         unsigned short* sbuffer = (unsigned short*) buffer;
 
         for (int i = 0, ix = row * width * 3; i < width * 3; ++i, ++ix) {
-            data[ix] = sbuffer[i] / 257;
+            data[ix] = (sbuffer[i] + 128) / 257;
         }
 
         break;
diff --git a/rtengine/imagefloat.cc b/rtengine/imagefloat.cc
index fb4ccae2e..7f84f1cab 100644
--- a/rtengine/imagefloat.cc
+++ b/rtengine/imagefloat.cc
@@ -335,9 +335,9 @@ Imagefloat::to8()
 
     for (int h = 0; h < height; ++h) {
         for (int w = 0; w < width; ++w) {
-            img8->r(h, w) = static_cast<unsigned short>(r(h, w)) / 257;
-            img8->g(h, w) = static_cast<unsigned short>(g(h, w)) / 257;
-            img8->b(h, w) = static_cast<unsigned short>(b(h, w)) / 257;
+            img8->r(h, w) = (static_cast<unsigned int>(r(h, w)) + 128) / 257;
+            img8->g(h, w) = (static_cast<unsigned int>(g(h, w)) + 128) / 257;
+            img8->b(h, w) = (static_cast<unsigned int>(b(h, w)) + 128) / 257;
         }
     }
 
diff --git a/rtengine/iplab2rgb.cc b/rtengine/iplab2rgb.cc
index 489ca60bc..843bdaa9c 100644
--- a/rtengine/iplab2rgb.cc
+++ b/rtengine/iplab2rgb.cc
@@ -117,9 +117,9 @@ void ImProcFunctions::lab2monitorRgb (LabImage* lab, Image8* image)
 
                 /* copy RGB */
                 //int R1=((int)gamma2curve[(R)])
-                data[ix++] = ((int)Color::gamma2curve[R]) >> 8;
-                data[ix++] = ((int)Color::gamma2curve[G]) >> 8;
-                data[ix++] = ((int)Color::gamma2curve[B]) >> 8;
+                data[ix++] = (static_cast<int>(Color::gamma2curve[R]) + 128) / 257;
+                data[ix++] = (static_cast<int>(Color::gamma2curve[G]) + 128) / 257;
+                data[ix++] = (static_cast<int>(Color::gamma2curve[B]) + 128) / 257;
             }
         }
     }
@@ -229,9 +229,9 @@ Image8* ImProcFunctions::lab2rgb (LabImage* lab, int cx, int cy, int cw, int ch,
 
                 Color::xyz2rgb(x_, y_, z_, R, G, B, xyz_rgb);
 
-                image->data[ix++] = (int)Color::gamma2curve[R] >> 8;
-                image->data[ix++] = (int)Color::gamma2curve[G] >> 8;
-                image->data[ix++] = (int)Color::gamma2curve[B] >> 8;
+                image->data[ix++] = (static_cast<int>(Color::gamma2curve[R]) + 128) / 257;
+                image->data[ix++] = (static_cast<int>(Color::gamma2curve[G]) + 128) / 257;
+                image->data[ix++] = (static_cast<int>(Color::gamma2curve[B]) + 128) / 257;
             }
         }
     }