Even though we post so much of our work these days on the internet and don't actually print and matt every image, it's nice to be able to present a photograph on the internet with the look of a fine art gallery print.
Here's how to create a matt around your image in a few easy steps: (Click on any image to enlarge)
Open your image in Photoshop. Be sure that your Layer's Palette is open. Go to Window>Layers to turn it on if it isn't already open. Duplicate your background layer. Command-J (Mac) Control-J (PC).
Next we are going to increase the canvas size to create the matt board look around the image. From the Image Menu choose Canvas Size. Make sure that the "relative" box is checked to turn it on. Add one inch to the width and the height.
Choose Image>Canvas size again. This time add .75 to the height but be sure that the top-center square is selected. This will add the space to the bottom of the image only. Many times you will see matt boards cut with a little more "weight" on the bottom. This also allows for room to add text if you'd like.
Now we're going to add an outline around the "matt opening". Command click on a Mac, Control click on a PC, on the top layer thumbnail. Go to the Select menu and choose Transform Selection. Now we're going to enlarge the selection to make a frame around the opening. To constrain the proportions, resize the selection from the center, be sure that you press and hold down the Option Key on a Mac, Alt Key on a PC. Drag one of the corner handles out to enlarge the selection. Press Return or Enter (PC) when you have the selection the size you want it.
In order to add a stroke line for this selection we need to Create a New Layer (bottom of the Layer's Palette). Go to the Edit Menu and choose Stroke. Make the width about 2 pixels wide and choose a color (or leave it black). Click OK and then deselect by pressing Command-D on a Mac, Control-D on a PC.
You can add a drop shadow to your stroke layer by adding a Layer Style (bottom of the Layer's Palatte). Choose Drop Shadow, click once on the drop shadow name to go to the drop shadow dialog box. Change any settings to your liking and hit OK to close the dialog box.
If you want to add text to the bottom area of your new matt simply choose the Type tool, center align your text and begin typing. Open your Type dialog box to make changes to fonts, sizes, colors, tracking, etc.
And of course, because you used layers in all of these steps, you can always go back and make changes if you wish. Just be sure to save your document as a PSD file to keep the layers in tact.