This is useful for getting an image onto a smaller SD CARD.
Use GParted and resize the existing data partition as small as you need/can.
Now use fdisk to work out the dimensions of the data:
sudo fdisk -l -u=cylinders /dev/sd?
Replace /dev/sd? with path to your device and once run take note of the Units byte total and alse the End point of the last partition as this is the last point on the sdcard we want to copy.
Now we can use dd to make an image:
sudo dd if=/dev/sdc of=~/pi-pres.img bs=7777280 count=331
where bs=<the Units from fdisk> and count=<the End of the last partition +1 to capture the last block>