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Most of you Mac users are probably aware of the screen capture features that are part of Mac OS X: the Grab utility, the keyboard shortcut commands and the screencapture command in Terminal. No?

Let’s look at the options:

Grab

The Grab application (Applications->Utilities->Grab.app) is a free, built-in screen capture program in Mac OS X that allows you to capture an area with the selection tool, a window, the whole screen and even the whole screen in Timed mode. The last option gives you time to move items or whatever for 10 seconds before taking the snapshot.

Keyboard Shortcuts

Keyboard shortcuts are a very fast way to snap screen captures once you memorized them:

• Command-Shift-3: Take a screen capture of the screen, and save it as a file on the desktop
• Command-Shift-4, then select an area: Take a screen capture of an area and save it as a file on the desktop
• Command-Shift-4, then space, then click a window: Take a screen capture of a window and save it as a file on the desktop
• Command-Control-Shift-3: Take a screen capture of the screen, and save it to the clipboard
• Command-Control-Shift-4, then select an area: Take a screen capture of an area and save it to the clipboard
• Command-Control-Shift-4, then space, then click a window: Take a screen capture of a window and save it to the clipboard

In Leopard (OS 10.5), the following keys can be held down while selecting an area (via Command-Shift-4 or Command-Control-Shift-4):

• Space – to lock the size of the selected region and move it with the mouse
• Shift – to re-size only one edge of the selected region
• Option – to re-size the selected region with its center as the anchor point

.

Terminal

Lastly, using Terminal (Applications->Utilities->Terminal.app):

Open a Terminal window and type the following, then hit the return button:

screencapture -S ~/Desktop/screen.png

This should save the “screen.png” file to your desktop.

The screencapture command in Terminal is very flexible and a bit more complicated than the two previously mentioned methods. Below is a bit of documentation on the command from the always-helpful MacRumors:Guides website:

The screencapture utility is not very well documented to date. A list of
options follows.
-S In window capture mode, capture the screen instead of the window.
-W Start interaction in window selection mode.
-c Force screen capture to go to the clipboard.
-i Capture screen interactively, by selection or window. The con-
trol key will cause the screen shot to go to the clipboard. The
space key will toggle between mouse selection and window selec-
tion modes. The escape key will cancel the interactive screen
shot.
-m Only capture the main monitor, undefined if -i is set.
-s Only allow mouse selection mode.
-w Only allow window selection mode.
-x Do not play sounds.
-C Capture the cursor as well as the screen. Only allowed in non-
interactive modes.
-t <format> Image format to create, default is png.
file where to save the screen capture

What hasn’t been explained so far is the anatomy of the command structure and the fact that the options shown above can be used in combination.

The anatomy of the command structure is:
[command][options][arguments]
e.g.
[screencapture] [-S] [~/Desktop/screen.png]
where “screencapture” is the command, “-S” is the option telling the command to capture the whole screen and “~/Desktop/screen.png” is the argument specifying the location and name of the file to be created.

As many options can be used in the [options] part of the structure as necessary to achieve the result you want with the command. Meaning that if you want to interactively select the window to be captured, you would use the argument “-iW” which is a combination of the “-i” and “-W” options. You would see a visual prompt for you to select the window you want to capture when you execute the command.

The options can be combined in any way that makes sense.

Pretty neat stuff so far, right?

One thing you may have noticed while using these tools is that there is a default file format for screen captures that is used by the OS. This default has changed with different versions of the Operating System:

• Mac OS X 10.2 (Jaguar): jpg
• Mac OS X 10.3 (Panther): pdf
• Mac OS X 10.4 (Tiger): png
• Mac OS X 10.5 (Leopard): png

There may be any number of reasons you would like to change the default format for the images to be saved. For one, pdf files are almost universally used by people. The same can be said for jpg and gif files.

Fortunately, there’s a pretty easy way to change this default and there are a number of formats to choose from — gif, jpg, tiff, pict, pdf and psd. The inherent quality and file size differs for each of these formats and you can choose the one that best suits your intended purpose for the capture.

So how do you change the default file type? In the Terminal, of course! Don’t worry – this one is a breeze.

Open a Terminal window and type:

defaults write com.apple.screencapture type jpg

Click the return key and then type:

killall SystemUIServer

Replace “jpg” with “pdf” or whichever file_type you want to use as the default.

That’s all there is to it!

There’s one more way to temporarily change the file_type on the fly but it only works when using the screencapture command in Terminal. In the list of screencapture utility options listed above, you should notice the “-t” option. This allows you to specify the format or file_type in the options of the command. The syntax would look something like this:

screencapture -S -t pdf ~/Desktop/screen.pdf

Note two important things:

1. “-t” is not combined with “-S” like the other options can be. Presumably, this is because “-t” has it’s own argument.
2. Both the format/file_type option’s argument and the file_name suffix match. If you aren’t careful to match these, you will end up with a file_name.suffix that isn’t the file_type it says it is! This is true of any of these screen-capture methods. If your default file_type is png, for example, and you name the file “screen.jpg” your file_type will actually be a png. This can have negative affects – the file might not open with the right application if when you double-click it’s icon or may not be recognized properly by some applications and not open.

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Tags: application, applications, change, default, file type, format, free, gif, Grab, Jaguar, jpg, keyboard shortcuts, Leopard, Mac, Mac OS X, options, Panther, parts, pdf, png, psd, screen capture, Terminal, tiff, Tiger, universal, website

This entry was posted on Thursday, December 11th, 2008 at 5:01 pm and is filed under Gizmos, Web Development. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.