What we’re doing is taking the same image and applying it to a new pixel grid this is called resampling and is usually what we mean when we talk about resizing images. Consider an image of a blue 4 × 4 pixel square that we want to double in size to 8 × 8 pixels. making images larger) can be a little easier to visualize, so let’s start with that. In other words, we need to figure out the best way to add or remove pixels without changing what the image looks like.Īlthough not as common a use case, image upsampling (i.e. The challenge is in figuring out the best way to store the original image’s content in this different number of pixels. If the image is being enlarged, the output will have more pixels than the input if the image is being shrunk, the output will have fewer pixels than the input. The best way to solve the problem is to understand why it’s happening, and that means understanding the basics of how image resizing works.īy definition, when a computer resizes an image, the number of pixels in that image will change. These big files completely negate the performance gains you’d expect to get from responsive images and, in fact, can make things worse for your users than if you’d simply loaded the huge unshrunk assets.īelow, I’ll describe why this problem exists and show you how to change ImageMagick’s default settings to solve this problem and get small, great-looking images. Unfortunately, with the default settings, the resized files it outputs are often really big - sometimes bigger than the inputted image, even though the output has fewer pixels. ImageMagick provides a fast, simple way to automate image resizing. Otherwise, look for it in your favorite package manager, or download it directly from the ImageMagick website. If you use Homebrew on a Mac, you can install it like this: brew install imagemagick It’s also available on desktop systems (Mac, Windows and Linux). It is widely supported by content management systems (CMS) such as WordPress and Drupal, integrated with task runners such as Grunt, and used on its own to automate image editing - including resizing. ImageMagick has been around for almost 25 years and is a full-fledged command-line image editor. A bunch of tools out there do this, including GD and GraphicsMagick, but ImageMagick strikes a good balance between power and availability in hosting environments. This is where automated image resizing comes in handy. But what about a large website with a lot of images? An online store, for example, might have hundreds or thousands of image assets, and having to create different sizes of each of these is an enormous task. Responsive images to the rescue! Right? Well, yes, but first we have to generate our responsive image assets, and we have to make sure those assets look good and have a small enough footprint to improve the website’s performance.įor a very small website, saving a few different sizes of each image directly in our image editor is trivial - Photoshop even provides a handy “Save for Web” option that keeps file sizes low. (Image: HTTP Archive) ( View large version) The average web page is 2,099 KB, 1,310 KB of which comes from images. Improving web performance and giving a better experience to our users is our job as developers and designers. Even on a fast connection, a 2 MB website can wreak havoc on your users’ data plans and cost them real money. At the same time, millions of people are accessing the Internet on 3G-or-worse connections that make a 2 MB website a horror show to use. When you are ready, click the “Optimize” button to start resizing your JPEGS.The average web page is about 2 MB in size, and about two thirds of that weight is from images. Set the “Save setting:” to either create new copies, which will make new resized copies of your images, or choose to replace the original files with the resized versions. You can also drag files onto the application to add them. Click OK.Ĭlick “Add files” to select files individually, or “Add folder” if all the images you want to resize are in a single folder or its sub-folders. We’d suggest picking 1920 x 1080 from the dropdown. Give the profile a name like “Resize JPEGs”, click on the JPEG tab, and check the “Resize images for display at:” box. This application comes with a 14-day free trial, that will allow you to resize your batch of images easily.ĭownload the free trial of NXPowerLite for Windows or Mac.Ĭlick on the Optimize profile dropdown, and select “New optimize profile…”. If you need to resize lots of images, you can use NXPowerLite Desktop. How to batch resize JPEGs using NXPowerLite
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