add NodeImageTexture for dynamic images, test image thumbnail opening and rendering

engine/image.h

@@ -6,12 +6,20 @@ class Image
 {
     std::unique_ptr<uint8_t[]> m_data;
 public:
-    int width;
-    int height;
-    int comp;
+    int width = 0;
+    int height = 0;
+    int comp = 4;
     bool load(std::string filename);
     const uint8_t* data() const { return m_data.get(); }
     int size() const { return width * height * comp; }
+    void create(int w, int h) 
+    { 
+        width = w; 
+        height = h;  
+        comp = 4;
+        m_data = std::make_unique<uint8_t[]>(size());
+    }
+    void create() { m_data = std::make_unique<uint8_t[]>(size()); }
 };
 
 }