The “Simple” Act of Resizing Images

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Recently, a faculty member asked me a question that initially didn’t appear to be difficult to answer. “How do you resize an image?” When I’m working on multimedia projects, I do it many times over, or at least I did. Actually now, it is greatly automated for me and very complicated to tell someone how to resize their image because it contains the generally unsatisfactory answer – it depends.

Let me start by answering when and why you would want to resize a digital image. The most common use of digital images is to post them to a web page for others to see. The most common images that we have to share are digital images from our cameras. We see images on web pages all the time and often they are images that came from a digital camera. People upload images to web pages all the time and the images look fine. So why is “how do I resize images for the web” a difficult question to answer? Well, the process of uploading an image hides the step of resizing the image. It is taken care of behind the scenes automatically. That original size image, if it came from a digital camera (one over 5 megapixels or so), would overwhelm a web page. You would have to scroll up and down as well as left and right to see all of the image (unless you have a super-high resolution, and physically large, monitor).

If you’ve ever uploaded an image to Facebook, Flickr, or any other image sharing site, your image may be resized several times. In the case of Facebook, you get what’s known as a thumbnail, an image that is literally not much bigger than your thumb. Your image also gets resized to a normal size image that is intended for your friends or family members to see. Flickr, on the other hand, goes a bit further, so they resize a given image to a thumbnail size as well as lots of gradually larger sizes up to the original size.

The next obvious question might be then, why wouldn’t you just use the image sharing sites to house your resized images. For most circumstances that is exactly what I recommend. For applications such as WordPress blogs (you know like UMW Blogs) there is the ability to easily insert your images in a post or a page by simply including the link to a Flickr image. However, if for some reason you need to resize your image to specific dimensions, here are some options for you. Keep in mind that not all image resizing algorithms are created equal. Some tools will simply do a better job at resizing than others.

  • The standard bearer program of image manipulation is Photoshop. However, at several hundred dollars for the full version, it is certainly overkill for doing simple image resizing. However, if you have the program anyway, you simply load your image, go to the Image menu, and choose Image Size… you can then change the width and/or height of your image.
  • If you are on a Mac, you already have a great image resizer built into your OS. It is the program called Preview. You know the one that displays your images when you double-click on them (it displays your PDFs as well). If you open an image using Preview, you can go to the Tools menu and choose Adjust Size… You can then change the width and/or height of your image, then choose File/Save As… Note that the quality of using Preview for resizing images is on par with Photoshop, and you can also do batch resizing (which means you can select multiple images and resize several at a time. If you’re using a Windows computer, you can start with the programs we recommend for editing images on Windows.

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