add <image ...> atlases support

src/maths/UVRegion.hpp

@@ -1,6 +1,8 @@
 #ifndef MATHS_UVREGION_HPP_
 #define MATHS_UVREGION_HPP_
 
+#include <cmath>
+
 struct UVRegion {
     float u1;
     float v1;
@@ -11,6 +13,14 @@ struct UVRegion {
     : u1(u1), v1(v1), u2(u2), v2(v2){}
 
     UVRegion() : u1(0.0f), v1(0.0f), u2(1.0f), v2(1.0f){}
+
+    inline float getWidth() const {
+        return fabs(u2-u1);
+    }
+
+    inline float getHeight() const {
+        return fabs(v2-v1);
+    }
 };
 
 #endif // MATHS_UVREGION_HPP_