How To Resample An Image Using PhotoShop


First go to Image/Image size/

1. Make sure the document size option "Constrain Proportions" is selected (width + height + resolution are linked).

2. Edit the resolution option to a reasonable image size; at this time, the width and height will increase.

3. Select option "Resample Image" (now, only width + height are linked) and edit width and height to the actual out-put size.
Apply the same procedure for the opposite effect.