diff --git a/loadrunable.cpp b/loadrunable.cpp
index c54ac99..b6192de 100644
--- a/loadrunable.cpp
+++ b/loadrunable.cpp
@@ -478,14 +478,17 @@ void LoadRunable::run()
 
         if(m_thumbnail)
         {
-            if(rawImage)
+            if(rawImage && rawImage->valid())
             {
+                rawImage->resize(THUMB_SIZE, THUMB_SIZE);
                 rawImage->convertToThumbnail();
-                QMetaObject::invokeMethod(m_receiver, "thumbnailLoadFinish", Qt::QueuedConnection, Q_ARG(std::shared_ptr<RawImage>, rawImage));
             }
+            QMetaObject::invokeMethod(m_receiver, "thumbnailLoadFinish", Qt::QueuedConnection, Q_ARG(std::shared_ptr<RawImage>, rawImage));
         }
         else
+        {
             QMetaObject::invokeMethod(m_receiver, "imageLoaded", Qt::QueuedConnection, Q_ARG(std::shared_ptr<RawImage>, rawImage), Q_ARG(ImageInfoData, info));
+        }
     }
     catch(std::exception e)
     {
diff --git a/rawimage.cpp b/rawimage.cpp
index 6e68607..1eee356 100644
--- a/rawimage.cpp
+++ b/rawimage.cpp
@@ -388,7 +388,11 @@ const void *RawImage::origData(uint32_t row, uint32_t col) const
 
 void RawImage::convertToThumbnail()
 {
-    m_thumbAspect = (float)width() / height();
+    if(!valid())
+        return;
+
+    if(m_thumbAspect == 0.0f)
+        m_thumbAspect = (float)width() / height();
     std::unique_ptr<PixelType[]> outptr = std::make_unique<PixelType[]>(THUMB_SIZE * THUMB_SIZE * 4 * sizeof(uint16_t));
     uint16_t *out = reinterpret_cast<uint16_t*>(outptr.get());
 
@@ -400,6 +404,7 @@ void RawImage::convertToThumbnail()
             {
                 int idx = (i*THUMB_SIZE + o)*4;
                 int idx2 = ((i * m_height / THUMB_SIZE * m_width) + (o * m_width / THUMB_SIZE)) * m_ch;
+
                 if(m_channels == 1)
                 {
                     out[idx] = out[idx + 1] = out[idx + 2] = in[idx2] * scale;
@@ -559,14 +564,84 @@ bool RawImage::pixel(int x, int y, double &r, double &g, double &b) const
     return true;
 }
 
-void RawImage::downscaleTo(uint32_t size)
+template<typename T>
+void boxResample(uint32_t w, uint32_t h, uint32_t ch, uint32_t oldw, uint32_t oldh, const uint8_t *in_, uint8_t *out_)
 {
-    /*if(size < width() || size < height())
+    if(oldw == 0 || oldh == 0)return;
+
+    const T *in = reinterpret_cast<const T*>(in_);
+    T *out = reinterpret_cast<T*>(out_);
+    float max = 255.0f;
+    if constexpr(std::is_same<T, uint16_t>::value)
+        max = UINT16_MAX;
+
+    float sx = (float)oldw / w;
+    float sy = (float)oldh / h;
+    float sx_ = (float)w / oldw;
+    float sy_ = (float)h / oldh;
+    float s = 1.0 / (sx * sy);
+    for(uint32_t y = 0; y < h; y++)
     {
-        double s = (double)size / std::max(width(), height());
-        cv::Size dsize(std::floor(width() * s), std::floor(height() * s));
-        cv::resize(m_img, m_img, dsize, 0, 0, cv::INTER_AREA);
-    }*/
+        for(uint32_t x = 0; x < w; x++)
+        {
+            float p[4] = {0.0f};
+            uint32_t xx = x * oldw / w;
+            uint32_t yy = y * oldh / h;
+            uint32_t xe = std::min((x + 1) * oldw / w, oldw - 1);
+            uint32_t ye = std::min((y + 1) * oldh / h, oldh - 1);
+            for(uint32_t o = yy; o <= ye; o++)
+            {
+                float cy = o * sy_ - y;
+                if(cy < 0.0f)cy = 1.0f + cy * sy;
+                else if(sy_ + cy > 1.0f)cy = (1.0f - cy) * sy;
+                else cy = 1.0f;
+                if(yy==ye)cy = sy;
+                for(uint32_t i = xx; i <= xe; i++)
+                {
+                    float cx = i * sx_ - x;
+                    if(cx < 0.0f)cx = 1.0f + cx * sx;
+                    else if(sx_ + cx > 1.0f)cx = (1.0f - cx) * sx;
+                    else cx = 1.0f;
+                    if(xx==xe)cx = sx;
+                    for(uint32_t z = 0; z < ch; z++)
+                        p[z] += in[(o * oldw + i) * ch + z] * cy * cx;
+                }
+            }
+            for(uint32_t z = 0; z < ch; z++)
+                if constexpr(std::is_floating_point<T>::value)
+                    out[(y * w + x) * ch + z] = p[z] * s;
+                else
+                    out[(y * w + x) * ch + z] = std::clamp(std::round(p[z] * s), 0.0f, max);
+        }
+    }
+}
+
+void RawImage::resize(uint32_t w, uint32_t h)
+{
+    if(!valid())return;
+
+    std::unique_ptr<PixelType[]> old_pixels = std::move(m_pixels);
+    uint32_t oldw = m_width;
+    uint32_t oldh = m_height;
+    m_thumbAspect = (float)m_width / m_height;
+
+    allocate(w, h, m_channels, m_type);
+
+    switch(m_type)
+    {
+    case RawImage::UINT8:
+        boxResample<uint8_t>(w, h, m_ch, oldw, oldh, old_pixels.get(), m_pixels.get());
+        break;
+    case RawImage::UINT16:
+        boxResample<uint16_t>(w, h, m_ch, oldw, oldh, old_pixels.get(), m_pixels.get());
+        break;
+    case RawImage::FLOAT32:
+        boxResample<float>(w, h, m_ch, oldw, oldh, old_pixels.get(), m_pixels.get());
+        break;
+    default:
+        qWarning() << "Resizing format not supported";
+        break;
+    }
 }
 
 std::pair<float, float> RawImage::unitScale() const
@@ -692,3 +767,8 @@ std::vector<RawImage> RawImage::split() const
 
     return planes;
 }
+
+bool RawImage::valid() const
+{
+    return m_width > 0 && m_height > 0;
+}
diff --git a/rawimage.h b/rawimage.h
index bd32015..ef5b4fd 100644
--- a/rawimage.h
+++ b/rawimage.h
@@ -97,13 +97,14 @@ public:
     void convertToGLFormat();
     float thumbAspect() const;
     bool pixel(int x, int y, double &r, double &g, double &b) const;
-    void downscaleTo(uint32_t size);
+    void resize(uint32_t w, uint32_t h);
     std::pair<float, float> unitScale() const;
 
     static std::shared_ptr<RawImage> fromPlanar(const RawImage &img);
     static std::shared_ptr<RawImage> fromPlanar(const void *pixels, uint32_t w, uint32_t h, uint32_t ch, DataType type);
     static size_t typeSize(DataType type);
     std::vector<RawImage> split() const;
+    bool valid() const;
 };
 
 //Q_DECLARE_SMART_POINTER_METATYPE(std::shared_ptr);