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Before we start the actual creation of the project, let's talk about each of the key technologies being used. There are four HTML5 or related technologies that are involved in creating this project: File API, drag and drop, localStorage, and canvas. Let's start by taking a closer look at File API. The File API allows you to interact with local files on the client side, something that's never been possible before. This means you can preprocess files that are being uploaded, which in turn means that we can show thumbnails of files, limit the upload by file size or type, and even show a progress bar.
Moreover, you can also store files for offline work. There are three key related objects: File(), FileReader(), and the XMLHttpRequest() object. File, as you might imagine, provides information about the file itself, including name, file size, and MIME type. FileReader reads in and can display image data, like a thumbnail. It can also get and output file names. Moreover, it can work asynchronously, which is what makes progress bars possible.
The XMLHttpRequest() is now at a level 2 enhancement. And this is what provides client side functionality for transferring data to the server. Now, it doesn't go all the way. It still needs a little assist from a server-side technology like PHP. It does have pretty good browser support though, and I highly recommend that you go to caniuse.com, and check it out under File API. When you do, you will see that support is almost universal, and everybody is waiting for IE 10 to appear.
This is what allows you to get information that is held within the object that is being dragged, and place it in the target. As you can see on caniuse.com, it's got really solid browser support. Now we turn to localStorage. localStorage you'll find is very straightforward to use, and it brings the ability for websites to keep track of a state without server-side coding. Unlike the cookie, it's stored in the browser cache and it has a much higher limit than cookies do.
It's basically a name/value pair structure that works with strings only. There are two simple commands, localStorage.setItem, which takes two arguments, the name of the item that you're setting, and its value; and localStorage.getItem only has one argument, and that's the name of the item that you are retrieving from storage. Really good browser support here. Caniuse.com refers to it as web storage. But you can actually search for it by localStorage. As you can see, it not only has current support, it's got a good deal of legacy support all the way back to Internet Explorer 8.
Finally, let's take a good, hard look at canvas. Canvas enables runtime graphics. So, rather than uploading in file image, you can create it on the fly. Both stroke and fill are independently supported, as are drawing basic primitives, such as lines, circles, and rectangles. You can also add text, and of course, bring in images. Perhaps its most powerful feature, however, is that it enables interactive graphic capabilities. And that's of great interest to designers who are looking for enhanced user experience options.
With canvas, you can combine layers of imagery, putting one photograph on top of another, you can apply graphic filters like a sepia tone, and you can allow the imagery to be manipulated, moving it, resizing it, rotating it, and so forth. And again, canvas has terrific browser support. But you can really use it today. It really looks like the UX Designer's toolbox got beefed up, doesn't it? And now, we're ready to put some of those shiny new tools to work, customizing photo cards.
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