Enlarging Your Digital Image’s Canvas
You can increase the size of your digital image’s canvas (a virtual backdrop for your image). Increasing the canvas for your image lets you add to that image. How you adjust the canvas varies from program to program. Look for information about canvas size, image background, or picture size in your software’s Help system. To adjust the canvas size in Photoshop Elements
Choose Image→Resize→Canvas Size.
The Canvas Size dialog box opens.
Enter the new canvas dimensions into the Width and Height option boxes.
You can select what unit of measure you want to use in the drop-down lists to the right of Width and Height.
Specify where you want to position the existing image on the new canvas by using the Anchor grid.
For example, if you want the extra canvas area to be added equally around the entire image, click the center square.
Select the color of the new canvas area in the Canvas Extension Color drop-down list.
The new canvas becomes the color you want.