Preview seems to get over looked by users, it seems half the time they don’t even realize they are using it, or how or why they are able to open the many image formats available. Maybe it’s the application name, it can be a bit confusing when saying things like “The image will load up in Preview”.

Well, of course it will.

One of the great things about Preview is its speed, the application loads up within a bounce or two and with a short wait for the image or pdf file to display. How many times have you double-clicked an image and Photoshop starts to load? Or double-clicked a PDF file and Adobe Reader started its crawl to load up your document? Oh the pain. Once your document is open, you have a number of editing options like cropping, resizing, rotation, text selecting (PDF only) and more.

Change File Type

If you come from the days of print, you might remember the multitude of files you had to deal with when moving them around. TIF was the norm, EPS was a pain to work with outside of Illustrator or Freehand. PDF was non existent and low res graphics were blasphemous in any format. Today PNG, JPG and GIF rule almost everything. Now that everything can read a web page, these files are essential to sharing information, thankfully Preview can not only read these formats, you can change an existing format into one of these.

Open an image file in Preview, now choose File->Save As. Now choose the desired format. It’s as easy as that. Extremely handy with so many users or clients out there demanding high-res JPG (no joke).

Image Editing

What do you think the number one operation on an image would be? I’d say crop & resize. For something you’d want done fast and easy, Preview is the tool. By default when images load up, your selection tool is ready. Just drag an area and choose Tools->Crop (Command+K).

Resize an image

Choose Tools->Adjust Size. The dialog shown has most of the same option as Photoshop and other image editing applications.

Crop an image

With your selection tool ready, just drag an area on the image. This should result in a dotted line with corner and side point which can be dragged for resizing your crop. The selection can also be moved to set a new position. Once the desired crop is set, hit Command + K (⌘ + K). A real downside to the crop tool is you cannot set the crop dimension by value, you’ll have to guess how big your selected area, there isn’t even any output to let you know the size of your selection, so id you need to crop to a specific size - Preview can’t do it.

Adjust Color

Did you know Preview offers some basic color adjustments? Just like in iPhoto it uses a floating display where you can adjust exposure, brightness, contrast, saturation, temperature, tint, sepia, black and white levels and sharpness. Need to quickly edit your exposure? Open it up in Preview and start tweaking, much faster than even having to load up iPhoto.

Masks and Alpha Channels

If you’re asking-- what’s an alpha channel, then you’ve probably never masked an image or had to do too much advanced work with an image. On the computer, images are broken down into “channels’ which are grayscale images. RGB images are composed of three channels: R, G and B (Red, Green, Blue). When a fourth channel is introduced, it can be used as a filter to mask out portions of the main composition where black is visible and white is hidden, and anything in between is a level of transparency. This is how you can create subtle transitions to another image or color behind your image.

Preview has some simple, but complex abilities to mask out an area of an image. Open up an image that you want to create mask with. I’ve loaded up a lake image. I’m going to remove the sky, so in my web page the background color, whose through which is white in this case.

Once your image is loaded, click the Select button in the toolbar, and hold to see a drop menu. Choose the Instant Alpha tool.



Upon choosing the tool, you’ll receive on screen instructions on using the tool.


With my crosshairs in place, I simply drag over my blue sky. You are going to see a selection start to grow as you drag, this is your selection being created. If you move too quickly your selection may grab too much, so a good idea is to zoom in and make small selections. Your mask can be created in small clicks, since each click will add to the selection.



Don’t worry too much about messing up, there are three ways to back out. Undo your last move (or as many moves), hold option and click on a selection to remove it in just the same way you add it and lastly if its too far gone, choose File->Revert to start over.

Once you have your selection set, press Return. A selection will fill the area of your image that still has pixel information. If you are done, choose File-Save As to save out a new document. For the web, choose PNG from the format menu, and make sure Alpha remains checked else it will not include the Alpha channel you just created.



If you’ve notice the Extract Shape tool, this works in a similar manner as the Instant Alpha tool, except you mask out using a selected area. Below I’ve drawn around the boat, and tweaked the points. Once I have the general area done, I can move in and tweak the mask using the Instant Alpha tool. The results are quite good without spending a lot of time.



These tools are excellent for simple masking with large areas of similar color, and it does an excellent job creating the mask. You don’t want to get images with too much around your subject, since there aren’t any retouching tools outside of these which end up being a bit blunt. This is where you’ want a pro tool like Photoshop. Another downside to viewing your mask is there is no way to see an image underneath your current image since layer are not supported (here’s hoping!).

More!

• From right in Preview, you can email your image to someone. Choose File->Mail Image and Mail app fires up with the image attached.
• If the image you are viewing is junk (and not in a artistic way), just hit Command+Delete to trash it, no going to the Finder necessary.
• Wondering what the dimensions of the image are? Choose Tools+Inspector or Command+I. You can get dimensions, DPI, color mode, file size, ColorSync profile and more.

PDF

Adobe’s Portable Document Format is the most popular format for sharing multi-page documents. Preview is the best PDF viewer out there. Forget annotating, marking up, versioning and all that - everyone just wants to 1) Read the file they just got in their email or 2) create one for someone to read.

Viewing

Preview is such a great PDF reader, mainly because of it’s speed. For sheer load time, Adobe Reader is a dog, and a sick one at that. It takes forever to load, and sucks up way too many resources (60MB with no file loaded). Preview flies through multi-page documents with barely a hiccup.

More!

• When viewing PDF files, almost all of your image editing tools are unavailable
• In a Multi-page document, cropping a page will crop only that page
• Crops do not destroy the image, you can view the rest of the image by choosing View->PDF Display->Media Box
• Preview doesn’t support much of the ‘pro’ features offered in Acrobat Professional, which means certain PDFs may not render properly (like embedded video).
• Forms are supported for viewing, not for creation

Create

With Preview, there’s not much to tell here, no big secrets or hidden options. It’s simply Save As and choose PDF for the format list. The only option to go with PDF is applying a Quartz filter to the file, which is just a visual effect, and you can encrypt your file so password protect your file.

That’s it. You can simply mail it off to whomever now.

A great little trick though is what if you have a handful of images you want to email or share? Instead of attaching a half dozen images, send as a multi-page PDF.

Open up a single image. Save As a PDF. The image will reload in the new format. In the toolbar, click the Sidebar button. This will show you a preview of your page.
Next select the rest of your images like this.

Drag them all to the sidebar. Preview loads them in as individual pages.
Choose File->Save. And like images, if you want to email it - choose File Mail Image.

Mark up and Annotate Tools

Preview offers some simple tools to work with a document. If you are drafting a document with multiple users and are passing around a document, Preview has text markup abilities and notes. The three markup options are Highlight, Strikethrough and Underline. The names are obvious what they do, just open up a PDF document containing text, then choose the Text tool in the toolbar. Drag your cursor over some text, choose Tools->Mark Up and choose the desired option.



The annotations allow you to place interactive elements onto your document. You can place hyperlinks, notes, rectangles and oval shapes. Choosing any of these options may stump you the first time, since there is no feedback from Preview as to what to do next. You are left with crosshairs though which you just drag out on your page to initiate.

The shapes are useful for marking or highlighting an area, kind of like a big marker. There’s not much more to say about this tool, its pretty straight forward.


The link tool drags out a shaded area which you need to provide the destination for the link. It can be either another page or a URL.



The last tool is the notes which works slightly different. Choosing a new note pops open a second drawer on the left side. If no notes are present it’s a blank gutter, but drag on your document, a note appears in the gutter where your cursor is, you can type your comment in the note.



Lastly, some options for the notes tool is the icon can be reflective of your note so it doesn’t have to be a comment, but an insert, new paragraph and more.



That’s it for now, I think I covered most of what Preview has to offer. Let me know what you thought of this.

Tags: Preview, PDF, Alpha, Masking