What is this Frame_Info for?

Why do't you use same style for typedef?
i.e.
typedef struct _Image_Frame Image_Frame;
or
typedef struct _Loader_Info
{
...
} Loader_Info

Please remove EINA_UNUSED

Please free memory of frame before return here.

Would you please add some comments why we need to use 0.1? What is the meaning of 0.1?

:-p
단수형은 datum이지만 전문 용어로는 흔히 복수형으로 쓰임
https://en.dict.naver.com/#/entry/enko/dca3a30f55114aa79876939b06b0f769

*error = ?;
Please set error before return.

*error = ?;
Please set error before return.

Please remove empty line.

You missed adding this examples in meson.build.

webp = dependency('libwebpdemux', required: get_option('evas-loaders-disabler').contains('webp') == false)

Does File_Info struct necessary? I think you can put the void* map into Loader_Info

EINA_LIST_FREE()?
where this frames are freed?

looks unnecessary.

Always animated??

q) what case frame->dealy == 0.0? and where DEFAULT_DURATION value come from?

I think you can use eina_array so that you can find the frame in O(1)

This is not good for loading time....
Is it possible to load frames on the demand?

When we get frame_count, we can reserve array with the size in advance.

Why don't you check return value of this WebPAnimDecoderGetNext?
No need to initialize buf?

@herb Could you please remove libwebp dependency?