Capturing Screen Images

In many instances, capturing an image of what is happening on your Mac's screen is useful. One example is if you are writing instructions about how to do a particular task, such as when you are writing your own book about Mac OS X. Another is when you want to capture an error message or some other anomaly you want to be able to explain to someone (for example, you might want to capture the image of an error dialog box so you can email it when you try to get technical support).

With Mac OS X, you have two built-in ways to capture screen images. One is to use keyboard commands. The other is to use the Grab application.

Capturing Screen Images with Keyboard Shortcuts

Mac OS X includes keyboard commands you can use to capture desktop images. After you capture an image, it is stored on your desktop as a PDF and is called Picture X, where X is a sequential number. You have the following three options:

  • Shift-graphics/mac.gif-3 captures the entire desktop.

  • Shift-graphics/mac.gif-4 changes the pointer to a plus sign. Drag this pointer to select the part of the screen you want to capture. When you release the mouse button, an image of the selected area is captured.

  • Shift-graphics/mac.gif-4-spacebar enables you to capture a window, menu bar, Dock, or other area of the screen. First, open the area you want to capture, such as a window or menu. When you press the key combination, a large camera pointer icon appears. Move this icon over the area that you want to capture, which becomes highlighted. Click the mouse button to capture the image.


To choose not to capture an image after you have pressed these key combinations, press Escape. If you want to save an image to the Clipboard so you can easily paste it into a document, hold down Control while you press the keys for the kind of screenshot you want to take.

Capturing Screen Images with Grab

Mac OS X includes the Grab application. As its name implies, using Grab, you can "grab" an image of your Mac's desktop. There are several options you can use to capture a specific image. To capture a desktop image follow these steps:

  1. Open Grab (Applications/Utilities).

  2. Select the Capture mode you want for your screenshot using the Capture menu. Your options are as follows:

    • Selection captures an area of the screen you select.

    • Window captures the active window.

    • Screen captures the entire screen.

    • Timed Screen provides a timer so you can set up a screen before it is captured (so you have time to switch to a window and open a menu before the image is captured, for example).

  3. Follow the instructions you see. For example, if you select Timed Screen, the Timed Screen Grab dialog box appears. Then open the area you want to capture, such as a document window with a menu open. When you are ready to take the shot, click Start Timer in the Timed Screen Grab dialog box and get the window as you want it to be captured. After 10 seconds have passed, Capture captures the image.

    When the capture is complete, you see a new window containing the image you captured.

  4. To see the size of the image you captured and its color depth, select Inspector from the Edit menu or press graphics/mac.gif-1. The Inspector window appears and you see information about the image.

  5. Save the image. Grab's default file format is TIFF.

The images you capture with Grab are just like images you create in other ways. You can open them in image-editing applications, preview them in Preview, print them, and so on.


Grab's capturing capabilities are provided to the OS so that other applications can use them. For example, if you are working in a Carbon or Cocoa application, you can easily grab an image of its screen by selecting the Services command from that application's menu. Then, select Grab and select the type of grab from the menu. When you release the mouse button, the image you captured is displayed. How it is displayed depends on the application from which you captured it. For example, if you grab an image while you are using TextEdit, a Rich Text Format (RTF) file is created. If you grab an image while using Preview, that image appears in the Pasteboard window.



If you are at all serious about capturing screen images, there is a much better solution than that which Mac OS X provides natively. The best screen capture utility for Mac OS X is Ambrosia Software's Snapz Pro X. This application provides numerous options for your screen captures and even enables you to capture QuickTime movies of movement on your desktop. Check it out at (All the screen captures in this book were taken with Snapz Pro X.)

    Part I: Mac OS X: Exploring the Core
    Part III: Mac OS X: Living the Digital Life