Mp3tag supports two methods for embedding cover art into the tag data area of a media file:
- by embedding the physical image file directly from the disk;
- by Windows Clipboard.
In case 1 the image file will be embedded "as is".
That means, an embedded image file with filesize of 25 KB enlarges the filesize of the media file by about 25 KB.
In case 2 the image file will be transported via the Windows Clipboard.
That means, at first a JPG compressed image file will be decompressed into a "Device-Independent Bitmap" (DIB), for example, a 500x500 24bit image's data size grows from compressed 25 KB to uncompressed 732 KB.
Afterwards when embedding from the Windows Clipboard into the media file, the bitmap image data will be compressed into the given JPG compressed format.
However, the initial compression factor get lost.