can anyone help me to write a script for resizing images that i can set padding like this image blew

[jahid30096762iy1t]

can anyone help me to write a script for resizing images so that I can set padding like this image blew the image should resize from path 1 or selection plz help me 

[jahid30096762iy1t]

Making a panel like this  screenshot  is excellent for my other images  that have different sizes so I can change them later when  needed