diff --git a/src/main_gui.cpp b/src/main_gui.cpp
index 1f0f8b8..a621ef4 100644
--- a/src/main_gui.cpp
+++ b/src/main_gui.cpp
@@ -98,6 +98,7 @@ int main(int argc, const char* argv[]) {
         i += 4;
     }
     const std::vector<Color> bbox_colors = {RED, GREEN, BLUE};
+    std::vector<freling::BoundingBox> packed_bboxes;
 
     Vector2 win_size = {800, 450};
     const int padding = 5;
@@ -120,16 +121,13 @@ int main(int argc, const char* argv[]) {
     SetWindowSize(win_size.x, win_size.y);
 
     const Vector2 b_size = {150, 30};
-    Button b_add_box = {{padding, padding, b_size.x, b_size.y}, "Add box"};
-    Button b_pack = {{padding * 2 + b_size.x, padding, b_size.x, b_size.y},
-                     "Pack rects"};
 
     while (!WindowShouldClose()) {
         BeginDrawing();
         ClearBackground(RAYWHITE);
 
         //
-        // Buttons
+        // Widgets: buttons, ...
         //
         if (GuiButton((Rectangle){padding, padding, b_size.x, b_size.y},
                       "Add Box")) {
@@ -139,7 +137,8 @@ int main(int argc, const char* argv[]) {
         if (GuiButton((Rectangle){padding * 2 + b_size.x, padding, b_size.x,
                                   b_size.y},
                       "Pack Rects")) {
-            std::optional<Frame> f_packed = pack(*in_frame, bboxes);
+            std::optional<Frame> f_packed =
+                pack(*in_frame, bboxes, packed_bboxes);
 
             if (packed) {
                 UnloadTexture(pack_texture);
@@ -179,10 +178,18 @@ int main(int argc, const char* argv[]) {
         // Packed image
         //
         if (packed) {
-            const int offset_x = in_offset.x + in_texture.width + padding;
-            DrawTexture(pack_texture, offset_x, in_offset.y, WHITE);
-            DrawRectangleLines(offset_x, in_offset.y, pack_texture.width,
+            Vector2 pack_offset = {in_offset.x + in_texture.width + padding,
+                                   in_offset.y};
+            DrawTexture(pack_texture, pack_offset.x, pack_offset.y, WHITE);
+            DrawRectangleLines(pack_offset.x, pack_offset.y, pack_texture.width,
                                pack_texture.height, BLACK);
+
+            int c = 0;
+            for (const auto& b : packed_bboxes) {
+                const auto& color = bbox_colors[c % bboxes.size()];
+                draw(b, pack_offset, color);
+                ++c;
+            };
         }
 
         EndDrawing();
diff --git a/src/pack.cpp b/src/pack.cpp
index 3e56622..505e259 100644
--- a/src/pack.cpp
+++ b/src/pack.cpp
@@ -16,21 +16,21 @@ void blit(const Frame& in_frame,
     assert(in_box.height() == out_box.height());
 
     const int data_width = in_box.width() * sizeof(Pixel);
-    const int in_row_size = in_frame.width * sizeof(Pixel);
-    const int out_row_size = out_frame.width * sizeof(Pixel);
+    const int in_row_size = in_frame.width;
+    const int out_row_size = out_frame.width;
 
     for (unsigned int i = 0; i < in_box.height(); ++i) {
-        const int in_offset =
-            in_box.left * sizeof(Pixel) + (i + in_box.top) * in_row_size;
-        const int out_offset =
-            out_box.left * sizeof(Pixel) + (i + out_box.top) * out_row_size;
+        const int in_offset = in_box.left + (i + in_box.top) * in_row_size;
+        const int out_offset = out_box.left + (i + out_box.top) * out_row_size;
+
         memcpy(out_frame.data + out_offset, in_frame.data + in_offset,
                data_width);
     }
 }
 
 std::optional<Frame> pack(const Frame& in_frame,
-                          const std::vector<BoundingBox>& bboxes) {
+                          const std::vector<BoundingBox>& bboxes,
+                          std::vector<BoundingBox>& packed_bboxes) {
     if (bboxes.size() == 0) {
         std::cerr << "No bounding box, cannot pack.\n";
         return {};
@@ -71,9 +71,12 @@ std::optional<Frame> pack(const Frame& in_frame,
     const auto& largest = sorted_bboxes[0];
     BoundingBox out_largest = {0, 0, static_cast<uint32_t>(largest.width()),
                                static_cast<uint32_t>(largest.height())};
+    packed_bboxes.clear();
+    packed_bboxes.push_back(out_largest);
+
     Frame packed_frame(largest.width(), largest.height());
     blit(in_frame, largest, packed_frame, out_largest);
-    return Frame(in_frame);
+    return packed_frame;
 }
 
 }  // namespace freling
diff --git a/src/pack.h b/src/pack.h
index 6fa007b..f4b6a72 100644
--- a/src/pack.h
+++ b/src/pack.h
@@ -9,6 +9,7 @@
 namespace freling {
 
 std::optional<Frame> pack(const Frame& in_frame,
-                          const std::vector<BoundingBox>& bboxes);
+                          const std::vector<BoundingBox>& bboxes,
+                          std::vector<BoundingBox>& packed_bboxes);
 
 }