Precision Screenshots of Moving Elements in OS X
It’s really easy to take a screen shot in OS X, and there are a few different ways to do so. If the object you want to capture is the screen itself, all you need to do is press Command + Shift + 3. You’ll hear the sound of a camera shutter and a moment later a new png image will appear on your desktop called ‘Picture 1.’
If you want to capture a portion of the screen rather than the whole thing, press Command + Shift + 4 and a set of crosshairs will appear. Drag the crosshairs until the portion of the screen you want to capture is highlighted and release. The shutter will sound and your screenshot will appear on your desktop.
A third option: if you want to capture a particular window on the screen, press Command + Shift + 4 and then the spacebar. Your crosshairs will transform into a camera icon which, when moved around the screen, will highlight the window it is over. Click the mouse to make your capture.
You’ll notice that the third method – window mode, it might be called – adds a translucent shadow around the window that you’ve captured. In most cases this should be fine, and moreover it looks quite slick, but if you don’t want the shadow, OS X offers you another way to capture elements on the screen. Open the utility “Grab” (Applications/Utilities/Grab) and select ‘Window’ from the ‘Capture’ menu bar menu. Take your window grab and save the file (Grab also lets you name your files before saving them) and you’ll have a shadow-free png.
Screenshots of objects in motion
If you begin to take a lot of screenshots, you’ll soon notice a limitation of the above methods, namely, that it is very difficult to precisely capture a screen element that is in motion. For instance, double clicking on the title bar of any application window will minimize it to the dock, and if you have “Genie Effect” selected in the dock preference pane, the window will minimize with a unique animation. How to capture a precise frame of this animation in a screen shot?
To get your screen shot, you’ll need to install some third party software, namely an application which can record video of what’s happening on your screen. I use SnapZ Pro, which is 69$, but iShowU, a similar software, is only 20$. Open your screen recording app and take a short video of the animation that you want to capture. Open the resulting movie in QuickTime, scrub to the frame you want, and drag the frame off QuickTime onto Preview in the Finder. The frame will open and you can then save it to the format of your choice. Presto:
