Huge filesize with bitmap

I notice that if a CDR file contains bitmaps in it, the file size would become unreasonably huge.

For example, I have a JPEG of 1.61MB. If I import the JPEG into a blank CDR file, with only the JPEG in the file, the CDR file size becomes 8.34MB.

I wonder what are the "excessive" information that is stored in the CDR file which causes the huge jump in file size.