In Photoshop, select the whole image (ctrl All) then Edit > Stoke. Select the "Inside" option. You can select the colour and the number of pixels width. A little trial and error should sort you out.
In Photoshop, select the whole image (ctrl All) then Edit > Stoke. Select the "Inside" option. You can select the colour and the number of pixels width. A little trial and error should sort you out.