Steps to reduce both sides of ps polygon: Open ps, create a new document, select a rectangular box selection tool, and choose any one to see what the size unit of your box selection tool is. Select Edit in the menu bar-> Preferences-> Usually, a setting window will pop up, then select the unit and ruler, and set the ruler R and the text Y in the unit as pixels. Finally, for testing, choose a rectangular marquee tool and choose any one to see if the size unit of your marquee tool becomes pixels. The border has been resized.