I have the same problem as you, and then I use the tool itools to delete all the photos in the album, and there is still G capacity. Then I thought that I installed a software called I Album to read comics, and then I found that the display program was 22M and the document was1g. Then I found the introduction of the program in the app Store, and found a passage in it: read from camera film, save to camera film, and transfer to other photo albums. Then I understood. This program takes up extra g capacity. I first imported the pictures from the PC into the album, and now I save them with other software, because Apple's default sorting rule is not by file name. So it's equivalent to one of my pictures. I saved it several times. A solution is being considered. But you already know why.

I already found out. Looking directly at the Apple folder with the tool of itools, I found that under Apple's default photo album, there are cartoons I imported before, and the corresponding file name of this cartoon is "Dragon Ball 1" directory, with all the pictures of1-kloc-0/0, and then there are two subfolders, one is previewed thumbnails, and the other is rearranged cartoons of 65438.

Slimming method: After importing the file, directly delete the photos in the photo library, and then use the itools tool to enter the Apple Album folder, delete the backup photos, and only keep one, so you can lose 2/3 weight.