How to access elements of a C++ image array (struct) with Lua?

[Jonathhhan]

I have an array of this struct (sd_image_t*) as the return value of a function:

typedef struct {
    uint32_t width;
    uint32_t height;
    uint32_t channel;
    uint8_t* data;
} sd_image_t;

In C++ I can call sd_image_t[n].data while with SWIG created Lua bindings I can only call sd_image_t.data (which seems to be a pointer to all data of the struct). Is there a way to wrap it, so that I can call it like in C++?
Could %naturalvar help in my case? https://www.swig.org/Doc1.3/SWIGPlus.html#SWIGPlus_member_data
Here I tried to describe my issue too: https://forum.openframeworks.cc/t/swig-lua-binding-for-accessing-elements-of-an-image-array/43429