2. Then click the "Image" option in the menu bar above PS, and click the "Image Size" option in the drop-down menu.

3. You can open the image size setting dialog box, click to unlock the width and height, and select the unit as "pixel".

4. Then enter the width of 200 and the height of 100 as required, and click OK.

5. You can set the opened picture to a picture size of 200 pixels wide and 100 pixels high.