rework on dat and spr loader

src/framework/graphics/texture.h

@@ -7,6 +7,7 @@ class Texture : public std::enable_shared_from_this<Texture>
 {
 public:
     /// Create a texture, width and height must be a multiple of 2
+    Texture();
     Texture(int width, int height, int channels, uchar* pixels = NULL);
     virtual ~Texture();
 
@@ -17,15 +18,16 @@ public:
     virtual uint getId() const { return m_textureId; }
 
     /// Copy pixels from OpenGL texture
-    uchar* getPixels();
+    std::vector<uint8> getPixels();
 
     int getWidth() const { return m_size.width(); }
     int getHeight() const { return m_size.height(); }
     const Size getSize() const { return m_size; }
     const Size& getGlSize() const { return m_glSize; }
 
+    bool isEmpty() const { return m_textureId == 0; }
+
 protected:
-    Texture() {  }
     uint internalLoadGLTexture(uchar* pixels, int channels, int w, int h);
 
     uint m_textureId;