Flexible Responsive Images

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Responsive Web design is the approach that suggests that design and development should respond to the user’s behavior and environment based on screen size, platform and orientation. The practice consists of a mix of flexible grids and layouts, images and an intelligent use of CSS media queries. As the user switches from their laptop to iPad, the website should automatically switch to accommodate for resolution, image size and scripting abilities. In other words, the website should have the technology to automatically respond to the user’s preferences. This would eliminate the need for a different design and development phase for each new gadget on the market.

Please also go through my previous article Responsive Web Designing, so that you can understand everything in a better way.

FILAMENT GROUP’S RESPONSIVE IMAGES

This technique, presented by the Filament Group, takes this issue into consideration and not only resizes images proportionately, but shrinks image resolution on smaller devices, so very large images don’t waste space unnecessarily on small screens. Check out the demo page here for flexible responsive images.

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This technique requires a few files, all of which are available on Github. First, a JavaScript file (rwd-images.js), the .htaccess file and an image file (rwd.gif). Then, we can use just a bit of HTML to reference both the larger and smaller resolution images: first, the small image, with an .r prefix to clarify that it should be responsive, and then a reference to the bigger image using data-fullsrc.

<code><img src="smallRes.jpg" data-fullsrc="largeRes.jpg"></code>

The data-fullsrc is a custom HTML5 attribute, defined in the files linked to above. For any screen that is wider than 480 pixels, the larger-resolution image (largeRes.jpg) will load; smaller screens wouldn’t need to load the bigger image, and so the smaller image (smallRes.jpg) will load.

The JavaScript file inserts a base element that allows the page to separate responsive images from others and redirects them as necessary. When the page loads, all files are rewritten to their original forms, and only the large or small images are loaded as necessary. With other techniques, all higher-resolution images would have had to be downloaded, even if the larger versions would never be used. Particularly for websites with a lot of images, this technique can be a great saver of bandwidth and loading time.

This technique is fully supported in modern browsers, such as IE8+, Safari, Chrome and Opera, as well as mobile devices that use these same browsers (iPad, iPhone, etc.). Older browsers and Firefox degrade nicely and still resize as one would expect of a responsive image, except that both resolutions are downloaded together, so the end benefit of saving space with this technique is void.

Demo URL: http://scottjehl.github.com/picturefill/

Picturefill supports a broad range of browsers and devices (there are currently no known unsupported browsers), provided that you stick with the markup conventions provided.

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