Open the Terminal and type

sudo apt-get install gimp-resynthesizer

Then enter your system super user password to download and install the gimp resynthesizer plug-in

* This picture is found from Google Image

Select the area where you want to resynthesized

After select the area,
Then select Filters > Enhance > Smart Remove Selection

Press “OK” to start resynthesized

Result1

The other method to resynthesized
select Filters > Map > Resynthesize

Press “OK” to start resynthesized

Result2

Both 2 methods have a little bit different from the others
Both of them will spend a lot of time if the selected area much larger
However, Resynthesizer cannot resynthesized with high accuracy if the image is too complex