When copying from the Tag Panel from one file and pasting to another the file size of the image is different. It's the same if you go into Extended Tags and right click on a cover image and then go to another file and paste into the image area. The pasted file is different.
Reproduction steps. Find album that you can test on. Let's say 10 songs in the album.
- With 'Tag Panel' visible.
- Highlight Songs 2-10 and remove album cover or covers.
- Right Click and Copy album cover from Song 1.
- Click on song 2 and via the Tag Panel and paste the cover into it.
- For me my original Song 1 cover of 100KB is now 303KB
- Save the tag in Song 2 that you just pasted into.
- Copy Song 2's new cover.
- Paste it into Song 3.
- For me the 303KB cover is now 311KB.
- Save the tag in Song 3.
- Do this untill the end of the album or stop now.
When I'm done doing this and I highlight all the songs it will say "Cover Varies". Even if I highlight any two songs it will say "Cover Varies".
After all the copy and pasting the cover size in this experiment stabilized at about 314KB to 315KB.
Using a program called IrfanView I looked at the image information of the covers that I extracted one by one.
The Song 1 original image was described as this "JPEG, progressive, quality: 80, subsampling ON (2x2)".
The subsequent image files that were extracted were described as this "JPEG, quality: 100, subsampling ON (2x2)".
Lastly IrfanView was able to count the number of unique colors. It started out at 198886 for Song 1's cover and went down to 185588 by the time I got to Song 10.
This actually isn't a problem for me because I always remove all covers in an album at one time. I also paste the same image into an album all at one time from an external file.
To sum it up. The Copying and Pasting in this manner isn't really putting the same exact image into the new location. It's putting an image that looks pretty much exactly like the original but internally it is slightly different.