What is the general logic for iOS app to save pictures to albums?

mainly encountered such a situation, from Weibo client (iOS) saved the same picture to the album many times, calculated photo hash found different. The same is true for the international version of Weibo. In addition, use Telegram to save the same picture many times.

because I don"t do iOS development, I want to know a little bit about the general logic of saving pictures in iOS? How does it cause the files actually saved to the device to be different.

Thank you for the answer.

Ios
Jul.29,2021
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