pishrink is a useful tool to reduce the size of dd images to it's minimum. When the image is booted the image expands the root partition to it's possible maximum size. You can shrink an image created by raspiBackup by using the helper script raspiBackupWrapper.sh. Following paragraph describes in detail how to configure raspiBackup to shrink dd backup images with pishrink.
First install and configure raspiBackup. See this page for details. When you managed to create a dd backup download raspiBackupWrapper.sh from github
sudo mv ./raspiBackupWrapper.sh /usr/local/bin
sudo chmod +x /usr/local/bin/raspiBackupWrapper.sh
Now download and install pishrink
sudo mv ./pishrink.sh /usr/local/bin
sudo chmod +x /usr/local/bin/pishrink.sh
Then activate /usr/local/bin/raspiBackupWrapper.sh
so it defines the used backup mount point.
and delete the leading #
Now test raspiBackupWrapper.sh
Finally change /etc/cron.d/raspiBackup
00 05 * * 0 root /usr/local/bin/raspiBackup.sh
00 05 * * 0 root /usr/local/bin/raspiBackupWrapper.sh
That's it :-)