Understanding Photoshop is a biweekly column that takes an in-depth look at how digital photographs are built and manipulated. It is a college-level course in plain English for free at Photofocus. To learn more see this article.
The canvas size is your work area. When you create a new document, you can specify the size of your canvas. When you scan a photo or import a digital image, the canvas size is automatically set to the edge of the image. You may need to change the canvas size to crop or extend the canvas of your image to work on specific areas of the image. Let’s try it out:
1. Open the file Canvas.tif.
2. Choose Image > Canvas Size or press Command+Option+C (Ctrl+Alt+C).
In the Canvas Size dialog box you’ll see the dimensions of your current canvas. You can specify a new canvas size using a variety of measurements. Pixels is a useful measurement if you’re creating screen graphics, whereas inches or centimeters is easier to understand for print work. Using percentage is also good for incremental amounts.
Let’s place a uniform border around the image.
3. Select the Relative check box. This disregards the numerical values of the current canvas size and allows you to specify a new amount to be added to the existing image.
4. Ensure that the anchor point for the image is set to centered. This will expand the border in all directions around the center of the current image.
5. Add a half-inch border on all sides. Type .5 inches into the Width and Height fields.
6. Specify a Canvas extension color. This is the color that Photoshop places around the image when you change the canvas size. You can choose to use the foreground or background colors that are loaded in the toolbox. You can also use white, black, gray, or other, which can be any color you specify. In this case, choose white.
7. Click OK.