diff --git a/rtengine/array2D.h b/rtengine/array2D.h
index 8d1351cbb..f4e5ac596 100644
--- a/rtengine/array2D.h
+++ b/rtengine/array2D.h
@@ -67,10 +67,10 @@ class array2D :
 {
 
 private:
-    ssize_t width, height;
+    size_t width, height;
     T** rows;
     T* data;
-    void ar_realloc(ssize_t w, ssize_t h, int offset = 0)
+    void ar_realloc(size_t w, size_t h, int offset = 0)
     {
         if (rows && (h > height || 4 * h < height)) {
             delete[] rows;
@@ -92,7 +92,7 @@ private:
             data = new T[height * width + offset];
         }
 
-        for (ssize_t i = 0; i < height; i++) {
+        for (size_t i = 0; i < height; i++) {
             rows[i] = data + offset + width * i;
         }
     }
@@ -105,13 +105,13 @@ public:
     { }
 
     // creator type1
-    array2D(int w, int h, unsigned int flags = 0) :
+    array2D(size_t w, size_t h, unsigned int flags = 0) :
         width(w), height(h)
     {
         data = new T[height * width];
         rows = new T*[height];
 
-        for (ssize_t i = 0; i < height; ++i) {
+        for (size_t i = 0; i < height; ++i) {
             rows[i] = data + i * width;
         }
 
@@ -121,7 +121,7 @@ public:
     }
 
     // creator type 2
-    array2D(int w, int h, T ** source, unsigned int flags = 0) :
+    array2D(size_t w, size_t h, T ** source, unsigned int flags = 0) :
         width(w), height(h)
     {
         const bool owner = !(flags & ARRAY2D_BYREFERENCE);
@@ -133,10 +133,10 @@ public:
 
         rows = new T*[height];
 
-        for (ssize_t i = 0; i < height; ++i) {
+        for (size_t i = 0; i < height; ++i) {
             if (owner) {
                 rows[i] = data + i * width;
-                for (ssize_t j = 0; j < width; ++j) {
+                for (size_t j = 0; j < width; ++j) {
                     rows[i][j] = source[i][j];
                 }
             } else {
@@ -157,7 +157,7 @@ public:
 #ifdef _OPENMP
         #pragma omp parallel for if(multiThread)
 #endif
-        for (ssize_t i = 0; i < width * height; ++i) {
+        for (size_t i = 0; i < width * height; ++i) {
             data[i] = val;
         }
     }
@@ -172,13 +172,13 @@ public:
     }
 
     // use with indices
-    T * operator[](int index)
+    T * operator[](size_t index)
     {
         assert((index >= 0) && (index < height));
         return rows[index];
     }
 
-    const T * operator[](int index) const
+    const T * operator[](size_t index) const
     {
         assert((index >= 0) && (index < height));
         return rows[index];
@@ -212,7 +212,7 @@ public:
 
     // useful within init of parent object
     // or use as resize of 2D array
-    void operator()(int w, int h, unsigned int flags = 0, int offset = 0)
+    void operator()(size_t w, size_t h, unsigned int flags = 0, int offset = 0)
     {
         ar_realloc(w, h, offset);
 
@@ -221,11 +221,11 @@ public:
         }
     }
 
-    int getWidth() const
+    size_t getWidth() const
     {
         return width;
     }
-    int getHeight() const
+    size_t getHeight() const
     {
         return height;
     }
@@ -243,7 +243,7 @@ private:
     array2D<T> list[num];
 
 public:
-    multi_array2D(int width, int height, int flags = 0, int offset = 0)
+    multi_array2D(size_t width, size_t height, int flags = 0, int offset = 0)
     {
         for (size_t i = 0; i < num; ++i) {
             list[i](width, height, flags, (i + 1) * offset);
diff --git a/rtengine/guidedfilter.cc b/rtengine/guidedfilter.cc
index 3f5e00e05..8429655dd 100644
--- a/rtengine/guidedfilter.cc
+++ b/rtengine/guidedfilter.cc
@@ -146,8 +146,8 @@ void guidedFilter(const array2D<float> &guide, const array2D<float> &src, array2
 #ifdef _OPENMP
 #               pragma omp parallel for if (multithread)
 #endif
-                for (int y = 0; y < s.getHeight(); ++y) {
-                    for (int x = 0; x < s.getWidth(); ++x) {
+                for (size_t y = 0; y < s.getHeight(); ++y) {
+                    for (size_t x = 0; x < s.getWidth(); ++x) {
                         d[y][x] = s[y][x];
                     }
                 }
@@ -164,9 +164,10 @@ void guidedFilter(const array2D<float> &guide, const array2D<float> &src, array2
     const auto f_mean =
         [multithread](array2D<float> &d, array2D<float> &s, int rad) -> void
         {
-            rad = LIM(rad, 0, (min(s.getWidth(), s.getHeight()) - 1) / 2 - 1);
-           // boxblur(s, d, rad, s.getWidth(), s.getHeight(), multithread);
-            boxblur(static_cast<float**>(s), static_cast<float**>(d), rad, s.getWidth(), s.getHeight(), multithread);
+            if (rtengine::min(s.getWidth(), s.getHeight()) > 1) {
+                rad = LIM<size_t>(rad, 0, (rtengine::min(s.getWidth(), s.getHeight()) - 1) / 2 - 1);
+                boxblur(static_cast<float**>(s), static_cast<float**>(d), rad, s.getWidth(), s.getHeight(), multithread);
+            }
         };
 
     array2D<float> I1(w, h);
@@ -249,8 +250,8 @@ void guidedFilterLog(const array2D<float> &guide, float base, array2D<float> &ch
 #ifdef _OPENMP
 #    pragma omp parallel for if (multithread)
 #endif
-    for (int y = 0; y < chan.getHeight(); ++y) {
-        for (int x = 0; x < chan.getWidth(); ++x) {
+    for (size_t y = 0; y < chan.getHeight(); ++y) {
+        for (size_t x = 0; x < chan.getWidth(); ++x) {
             chan[y][x] = xlin2log(max(chan[y][x], 0.f), base);
         }
     }
@@ -260,8 +261,8 @@ void guidedFilterLog(const array2D<float> &guide, float base, array2D<float> &ch
 #ifdef _OPENMP
 #    pragma omp parallel for if (multithread)
 #endif
-    for (int y = 0; y < chan.getHeight(); ++y) {
-        for (int x = 0; x < chan.getWidth(); ++x) {
+    for (size_t y = 0; y < chan.getHeight(); ++y) {
+        for (size_t x = 0; x < chan.getWidth(); ++x) {
             chan[y][x] = xlog2lin(max(chan[y][x], 0.f), base);
         }
     }