How to shrink SD card image?

After making an SD card following the guide on eeWiki, I make an image of it with Win32 Disk Imager using its Read feature. The problem is it image everything even the unused space. I found a guide to shrink the image here:

However, the configuration shown on my image is totally different from that one:

abc.img: DOS/MBR boot sector; partition 1 : ID=0x83, active, start-CHS (0x80,0,1), end-CHS (0x3cf,3,16), startsector 8192, 62510080 sectors

Can someone please show me how to shrink my image?

OK, I found this easy to follow guide:

Just need to install GParted and follow the steps.

Once the image is burned into the SD card, use GParted resize operation to reclaim unused space. Voila.