I've played around with a variety of online image editors, but "played" should be the operative word. For any serious image-editing work, I've always used traditional software methods. I hadn't found a Web service that could replace my usual standby apps (Photoshop at work, and Paint.NET at home) ... until I tried the new Web-based rsizr this weekend. I was blown away by its speed and ease of use in resizing and cropping digital images.
Even cooler than those basic-yet-essential functionalities are the app's flexible image-sizing features. Rsizr uses an algorithm called "seam carving" to expand or contract images in any direction while maintaining focus on the areas rich in detail. In essence, it lets you stretch or condense pictures without making them look blurry or smooshed. With a bit of practice, you can also perform the trick of removing people or objects from photos.
If you don't have the latest version of Adobe Flash Player, you'll need to update it before you start working withh rsizr. The Flash-based interface begins very simply, as if someone at rsizr attended the Google school of design. A simple "open" icon and the phrase "open a picture to get started!" comprise the entire welcome screen. There's only one way to get started, so dive in by opening an image file from your hard drive. The rsizr app supports JPG, JPEG, GIF, and PNG formats.
After opening your selected image (only one image can be active at one time), the interface suddenly becomes more complicated. Also, there's no help or instructional content within the app itself, which may prove frustrating to new computer users. The controls are placed in set of tabs across the upper-right of the interface, and there are four levels, though the tabs aren't quite arranged hierarchically.
The first set of tabs is akin to your standard "file" menu. Open a new picture, save your current image, or revert your image to its original state when you uploaded it. The second level of tabs is likewise persistent through the app. Magnifying glass buttons let you zoom in or out, and left and right arrow buttons rotate your image 90 degrees clockwise or counterclockwise.
The third set of tabs includes the app's bread-and-butter features: rescaling, cropping, and "retargeting." Rsizr defaults to the retargeting tab, which also includes a set of subtabs that I'll get back to in a moment. Clicking on either the "rescale" or "crop" buttons will bring up a dialog window within the main rsizr window.
Although the rescale dialog shows the height and width of your image, you can't simply type in new values. To resize an image, you must drag any of eight anchors on the image itself. Selecting the "Maintain Proportions" checkbox or holding down the Shift button while dragging an anchor will maintain the proportions of your picture. It's easy enough to drag a corner or side of an image to reach your desired size, but it would be even easier to be able to enter height and width values manually.
Cropping images works wonderfully, at least for rectangles. Conventional crosshairs let you select any area of your image, and a window on the right of the interface displays the size of your selection. There's no "undo" button in rsizr, but both the rescaling and cropping tools include a reset button that will revert your image back to the state it was in when you opened that particular tool. The main "revert" button at the top of the interface will change your image back to its state when you uploaded it--a critical difference.
The last feature in rsizr is definitely the coolest, and the one that sets it apart from other online photo editors. Selecting "retarget" from the third set of interface tabs will bring up two slide bars on the top and left of your image, as well as a subset of tabs for controlling the process of seam carving.
As mentioned above, seam carving is an intelligent algorithm that rsizr uses to identify the critical parts of your image, typically those areas that are very detailed. The top and left slider bars let you specify which areas of the image you plan to compress or expand. After analyzing the "seams" of your selected areas--which can take a few moments depending on the size of your image and area sected--rsizr will then use that data to intelligently enlarge or shrink your image as you see fit.
While that's cool enough on its own, two other features make it even more valuable. If you want to remove an object or person from a photograph, you can select the "remove" tool and paint over the item before you run the rsizr retargeting function. Likewise, a "preserve" button lets you specify the areas of the image that you want to leave intact, as much as possible.
Using these two tools in conjunction can quickly remove an unintended object from any photograph, as demonstrated very elegantly in the rsizr gallery, and much less elegantly in my "missing polar bear" image to the left. An "eraser" tool lets you erase any of your existing remove or protect selections, and I'm not exactly sure what the first tab button, a diagonal arrow tool, is for. I thought it might be for maintaining the aspect ratio of your image when retargeting, but that doesn't seem to be the case. If you figure out what it does, tell me in the comments.
Watch this video below about seam carving to learn more about the technology behind rsizr, or better yet, try it out yourself and tell me what you think.