file size of cover art varies how i add

  1. i get an image file to add it as a cover art for a music file.
  2. i edit it and finish making a jpg file. (for example, its size is 1.5mb.)

3-1. if i drag the jpg file itself from windows explorer into mp3tag, 1.5mb goes into the file currectly.
3-2, but if i open it with windows paint or faststone image viewer and copy and run 'paste cover' on mp3tag, the file size lessens (about 1.2mb or less).

i don't understand why this issue happens.
this means that file size and image quality get down if i use the way of 3-2???

You are sure?
It should be just the other way round.

You always have to use drag&drop or the right-mouse-klick/add or an action of th type "Import Cover from file". If you use the clipboard the cover increases in storage size.

/t/9422/1

Maybe this topic helps

/t/16012/1