If you have a group of pictures that are orientated incorrectly that you need rotated, you can do that in Mac OS X without any third party apps with the help of the bundled Preview app.

1. From the OS X Finder, select the collection of images you wish to rotate and hit Command+O to open them all into Preview
2. In Preview, click an image thumbnail in the sidebar and then hit Command+A to “Select All”
3. Now hit Command+R to rotate the picture 90 degrees clockwise once, hit Command+R again to continue rotating until you find the desired orientation of the pictures. Notice while this is happening that all thumbnail images are rotating.
4. Hit Command+S to save the changes to image orientation

This assumes your default image editor is set to Preview. If not, launch Preview separately and then drag the group of images into Preview to perform the same task.

Preview is a fairly powerful app that is often underutilized for batch photo processing tasks, I use it frequently to batch resize images for wallpaper posts and other purposes, it’s quick, lightweight, and much less demanding on resources than Photoshop for such tasks.

Preview in Mac OS X Lion brought with it several improvements and new features like digital signatures, but it also removed some very useful abilities like the file size estimator, Save As, and added the sometimes obnoxious Auto-Save.

If you miss the old version of Preview from Snow Leopard, and you either have a Mac OS X 10.6 Snow Leopard machine or backup handy, you can restore the older version of Preview (5.0.1) from Snow Leopard to run in OS X 10.7 Lion. Here is how to do this without replacing the OS X Lion version of the app (5.5.1), just in case you want to go revert to the newer version again.

1. From Snow Leopard, make a copy of these folders and transfer them to the desktop of the Mac OS X Lion machine:

/Applications/Preview.app
/System/Library/PrivateFrameworks/MeshKit.framework/

2. From OS X Lion, rename the old Preview.app to something else like “PreviewSnow.app”
3. Copy PreviewSnow.app to the /Applications/ folder in OS X Lion
4. Copy “MeshKit.framework” to /System/Library/PrivateFrameworks/ in OS X Lion and authenticate the change – this folder should not exist on the Lion machine already and you will not be overwriting anything else

Launch PreviewSnow.app from /Applications and it will run as usual, minus the frustrating Lion features and feature removals. If you want to set PreviewSnow.app as the new default app, right click on an image filetype, select “Get Info” and under the “Open With” menu find PreviewSnow.app and then click the “Change All” button underneath:

A true “Save As” is also back with this version, which is better than using the Export or Duplicate functions for many of us.

Preview is an often underused Mac OS X app that can handle a lot of file and image conversion tasks without the need for downloading any third party tools. Preview also happens to be the default PDF viewer in Mac OS X, and as such it can be used to easily convert any PDF file to a JPG, while still preserving the appearance and structure of the PDF.

Assuming you haven’t installed Adobe Acrobat Reader, Preview will be the default PDF viewer in Mac OS X. If it’s not, open the file in Preview anyway.

• Launch Preview from the /Applications/ folder and open the PDF that needs to be converted
• Pull down the “File” menu and select “Export” (if you mapped Export to the “Save As” shortcut just hit Command+Shift+S)
• From the ‘Export As’ window, click the contextual menu next to “Format” and choose “JPEG”
• Adjust the quality or resolution if necessary, and then hit “Save”

That’s all there is to it, the new JPG will be in the same directory as the PDF it came from unless you specified otherwise.

Thanks for the tip idea Shawnie

Mac OS X and several default apps have a built-in ability to quickly search the web. Highlight any text in the Finder, Preview, or TextEdit, and then hit Command+Shift+L to launch Safari with a Google search for the highlighted text selection.

The web browser will be set to Safari regardless of your default browser settings and doesn’t appear to be customizable. However, you can select either Google, Bing, or Yahoo as the search engine for the keyboard shortcut by going into Safari’s Preferences:

Other apps beyond the three mentioned likely have the same ability, but the Command+Shift+L keyboard shortcut in Safari opens Reading List rather than searching the web.

If you’ve downloaded Adobe Acrobat on the Mac you’ve probably discovered that it takes over Preview as the default PDF viewer in OS X, which is annoying because Acrobat is slow to load and a fairly bloated application. There’s little need to use Acrobat Reader as the way to view PDF files, so here’s how to change it back to Preview.

Change the Default PDF Viewer in Mac OS X

• From the Mac OS X desktop, find a PDF file and hit Command+i to “Get Info” on the file
• Click on the arrow next to “Open with:” to expand and access the default application list
• Click the pull-down menu and choose “Preview” from the list, or if it’s not visible, navigate to it by choosing “Other”
• With Preview.app selected, click on the “Change All” button

This will restore the leaner and very capable Preview app as the default PDF viewer in OS X and prevent the lengthy launch of Acrobat anytime a PDF is opened. This tip will be of less use if you need the full functioned Acrobat version, but for the average person just looking to quickly open pdf docs this can be a significant time saver.

If you want a quick PDF file to use for this tip, you can grab the Apple history book “The Macintosh Way” for free (direct PDF link).

With Preview you can adjust the contrast of a PDF, this makes the text sharper and darker, and for scans or dubious quality PDF’s this makes them significantly easier to read.

• Open the PDF with Preview
• From the ‘File’ menu, choose “Export”
• Click on the “Quartz Filter” drop-down menu and choose “Lightness Decrease”
• Choose “Save”

For a very practical example, I noticed this was sorely needed after downloading Guy Kawasaki’s freely available “The Macintosh Way” book, which is a great look at early Apple history. Unfortunately the PDF’s text is very light making it difficult to read, but the Quartz Filter mentioned above greatly helps this. The downside you may notice with some files (including The Macintosh Way) is an increase in noise. That noise is most noticeable on older PDF’s of scanned books or documents, and at times the trade-off may not be worth it.

Preview in OS X Lion has been updated to include a helpful magnification tool that follows the mouse cursor. To activate it, just hit the ~ (tilde) key with an image open in Preview, then by using the trackpad you can pinch or spread to increase or decrease the size of the magnifier.

This is pretty useful and offers a much more precise option than zooming in on a full sized image with the command + and – shortcuts and then navigating around.

Thanks for the tip Alejandro

Preview in OS X Lion now includes the ability to capture screen shots directly within the app, with the resulting images opening directly into Preview rather than saving to the Mac desktop. There are three different capture modes available that are almost identical to the standard keyboard shortcuts, here’s how to use them:

• Launch Preview
• From the “File” menu select “Take Screen Shot” and choose one of three options:
• From Selection – brings up the selection tool, just like command+shift+4
• From Window – enables the window selection tool, like command+shift+4+spacebar
• From Entire Screen – capture the entire screen (or both screens if you’re using two), same as command+shift+3
• The screen shots launch automatically into Preview where they can be cropped, manipulated, and saved. All of this is instant with the exception of capturing the entire screen, which causes a timer to be displayed

The timed screen shot feature was previously limited to the Terminal or Grab, but it’s pretty handy to have directly in Preview, with the countdown timer showing up in the center of the screen like so:

Update: Apparently this feature exists in the 10.6 Snow Leopard version of Preview as well, thanks for the heads up Makeup!

Mac OS X Lion brings a revamped Preview app that includes the extremely useful Digital Signature feature built right in. Using your Macs built-in iSight camera to capture your signature, Preview can keep multiple electronic signatures on file which can then be appended to PDF’s.

Setting a Digital Signature in OS X Lion Preview

• Launch Preview, and from the Preview menu select “Preferences”
• Click on “Signatures” and then “Create Signature”
• Write your signature on a piece of white paper and hold it up to the camera, try to have it somewhat straight on the blue line and watch the “Signature Preview” pane until you are satisfied with the way it looks
• Click on “Accept” to capture the digital signature

Now you can access and stamp your signature onto any PDF files opened within Preview. Technically you can store multiple signatures, so if you want to set additional ones or if your signature has changed, it’s the same steps as above.

Using the Digital Signature in OS X Lion Preview

• Open the PDF file you want to sign
• Click on the Annotations button (pencil icon) followed by the Signatures button (see image below)
• Now click within the document where you want the signature to appear

Voila, once the PDF is signed, just save the document and it’s ready to be used.

This works quite well and it’s a lot faster than printing out, signing, then scanning or faxing a document just so you can get your signature onto something. If you haven’t set your elecronic signature yet in Mac OS X, do it, it’s a very useful feature.

Using the same trick to create a new image file based on clipboard contents, you can extract high resolution icons from any Mac OS X application. Preview is smart enough to extract just the icon and not try to copy the app file itself (like Windows would).

• Select any app in Mac OS X Finder and hit Command+C to copy to clipboard
• Launch Preview and hit Command+N to create “New from Clipboard” (alternatively, use the File menu)
• Save the app icon as an image of your choice

This trick is great because it extracts each size variation of the icon automatically, giving you the full resolution range ranging from the tiny thumbnails up to 512×512 pixels, assuming the developer created an icon at that resolution.

Graphic designers and artists should be particularly fond of this one, as it allows you to easily inspect icons at their full resolution to see how they’re crafted.