Let us start here, from square one. No, from Zero!

external/layeredfs/texture_packer.cpp

@@ -0,0 +1,69 @@
+#include "texture_packer.h"
+
+#include <algorithm>
+
+#include "3rd_party/GuillotineBinPack.h"
+
+using namespace rbp;
+
+namespace layeredfs {
+
+    Bitmap::Bitmap(const string &name, int width, int height)
+            : name(name), width(width), height(height) {
+
+    }
+
+    bool pack_textures(vector<Bitmap *> &textures, vector<Packer *> &packed_textures) {
+        std::sort(textures.begin(), textures.end(), [](const Bitmap *a, const Bitmap *b) {
+            return (a->width * a->height) < (b->width * b->height);
+        });
+
+        // pack the bitmaps
+        while (!textures.empty()) {
+            auto packer = new Packer(MAX_TEXTURE);
+            packer->Pack(textures);
+            packed_textures.push_back(packer);
+
+            // failed
+            if (packer->bitmaps.empty())
+                return false;
+        }
+
+        return true;
+    }
+
+    Packer::Packer(int max_size)
+            : width(max_size), height(max_size) {
+
+    }
+
+    void Packer::Pack(vector<Bitmap *> &bitmaps) {
+        GuillotineBinPack packer(width, height);
+
+        int ww = 0;
+        int hh = 0;
+        while (!bitmaps.empty()) {
+            auto bitmap = bitmaps.back();
+
+            Rect rect = packer.Insert(bitmap->width, bitmap->height, false,
+                                      GuillotineBinPack::FreeRectChoiceHeuristic::RectBestAreaFit,
+                                      GuillotineBinPack::GuillotineSplitHeuristic::SplitLongerAxis);
+
+            if (rect.width == 0 || rect.height == 0)
+                break;
+
+            bitmap->packX = rect.x;
+            bitmap->packY = rect.y;
+            this->bitmaps.push_back(bitmap);
+            bitmaps.pop_back();
+
+            ww = std::max(rect.x + rect.width, ww);
+            hh = std::max(rect.y + rect.height, hh);
+        }
+
+        while (width / 2 >= ww)
+            width /= 2;
+        while (height / 2 >= hh)
+            height /= 2;
+    }
+}