added opacity to sprite

include/arc/graphics/sdl/sprite.h

@@ -9,6 +9,8 @@ struct ARC_Sprite {
     ARC_Spritesheet *spritesheet;
     ARC_Array       *frames;
     uint32_t        *frameIndex;
+    //TODO: temp
+    uint8_t          opacity;
 };
 
 #endif // !ARC_SDL

include/arc/graphics/sprite.h

@@ -42,6 +42,18 @@ void ARC_Sprite_Destroy(ARC_Sprite *sprite);
  */
 void ARC_Sprite_Copy(ARC_Sprite **newSprite, ARC_Sprite *oldSprite);
 
+//TODO: temp
+/**
+ * @brief sets ARC_Sprite's opacity
+ *
+ * @param sprite  ARC_Sprite that is changing opacity
+ * @param opacity new opacity for ARC_Sprite
+ *
+ * @note this is temp because opacity probably should be a value
+ *       bigger than 255
+*/
+void ARC_Sprite_SetOpacity(ARC_Sprite *sprite, uint8_t opacity);
+
 /**
  * @brief renders ARC_Sprite type
  *