Compress Photos with Photoshop’s Content-Aware Scale
Many Photoshop users are familiar with the Content-Aware Fill and Content-Aware Move features, but are less familiar with the Content-Aware Scale command. The Content-Aware Scale command comes in handy when you have a relatively empty area of your photo that you want to compress. It lets you squeeze that space, but it does so in a way that usually looks good.
Take, for example, the sunset photo of the surfers above. There’s nothing wrong with the shot, but what if you wanted to put the two surfers side-by-side? That might seem an obvious use for the Content-Aware Move tool and it might work here. But when I tried it, I ran into some issues with blending the source area into the destination area. Adobe’s addition of the Adaptation enhancements earlier this year provides a tool which helps to reduce those blending problems, but it doesn’t always eliminate them. In the image below, I’ve adjusted the Adaptation Structure and Color parameters to reduce the blending/matching problems as much as possible. But there is still a visible outline around the surfer on the left.
Content-Aware Move or Content-Aware Scale?
What if you wanted to change the aspect ratio of your photo? With Content-Aware Move, you could move one of the surfers and then crop the image as I’ve done above. But let’s say you like the skyline in this photo and would prefer to just squeeze the photo horizontally. That’s where Content-Aware Scale can help. I’ve used CAS in the image below to do just that—and without squeezing the people. I’ve reduced the photo below to 65% of its original width. (All the photos are shown here at 650 pixels wide to fill the space available on this web page. The scaling and moving were done on the original, larger files and then resized for output to the web.)
Getting the Most out of Content-Aware Scale
The key to compressing a scene without distorting important subjects like people is to protect them using a selection. You can try CAS without a selection and it will probably do a better job than simply using Free Transform. But, to really unlock the power of Content-Aware Scaling you need to create a selection.
In most cases, this is easy to do because you don’t need a precise selection. What you need to do is just outline the area that you don’t want to be compressed. Here are the steps for Photoshop CC 2014:
- First, make sure you’re not working with a Background layer. If you are, either create a copy of the layer or unlock the Background layer by clicking on the Lock icon in the Layers panel.
- Select the area you want to protect. You can use any of Photoshop’s selection tools for this purpose. In the sunset photo, I used the Elliptical Marquee tool to create two circles containing the two surfers.
- Save the selection as an alpha channel. You can do this either from the Channels panel or by choosing ‘Save Selection’ from the Select menu.
- Choose Deselect from the Select menu.
- Start Content-Aware Scaling by choosing it from the Edit menu.
- In the Protect drop-down in the options bar, choose the channel you just saved. Here, I’m choosing a channel I named “Surfers.”
- Adjust the image to the desired size.
In most cases, that’s all there is to it. If you’re making a major change to the height or width of your photo there may be some artifacts visible at the “seams.” If you do have this problem you might need to do some manual cleanup using tools like the Clone Stamp tool or the Patch tool.
Notice in the screenshot above there is a person icon at the right of the drop down. If you click this icon, it will tell Photoshop to watch for people and not compress them. This feature works best when people are distinct from the background and when making small size changes to your photos. It’s often worth a try because it can save you the steps of creating and saving a selection.
Featureless, Uniform Backgrounds Work Best
In order for Photoshop’s Content-Aware Scale feature to work well, you have to have a relatively featureless background. The ocean is an ideal subject; another example is the green hillside in the photo above. In this photo, I’ve protected the Swiss chateau, the catamaran and the trees nearby by simply drawing out a rectangle with the Rectangular Marquee tool. Here’s what the image looks like after being compressed by 20% vertically.
Sometimes, Content-Aware Move is the right tool for the job, while other times Content-Aware Scale is. Quickly creating a mask channel allows you to do a great job of protecting important content with CAS. In my work, I haven’t found any need to feather my selections.
CAS can come to the rescue when you need to fit a photo into a web page or magazine article layout, for example. You can also use CAS to stretch out a photo. This is a less common use, but could come up, for example, in a case where you need a wider or taller image to fit a specific page layout. In this case, you would need to increase your canvas size (Image —> Canvas Size or Image -> Reveal All).
Do you use the Content Aware Scale in Photoshop?