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Accessibility on the web has been an issue for over a decade, and it remains a crucial--but often overlooked--element of web design. Instructor Zoe Gillenwater explains the concept of accessibility as it applies to the web, and describes how it affects the audience. She also covers how to set up accessibility testing, and how to apply accessibility principles to new and existing sites using standards-compliant markup and CSS. Exercise files accompany the tutorials.
>> Now let's look at some accessibility tools that are online that you can bookmark and use for testing your pages. Four of these tools are listed on the screen with their URLs. You may want to pause the movie at this point to write them down and load them in your browser. I'm going to use the same page from the W3C that we've been testing in these four tools. The URL of it again is www.w3.org/wai/eo/2005/demo/before/index.
Go to the address bar and hit Ctrl C or Cmd C to copy the URL. Then open up the first tool at the URL colorfilter.wickline.org. This tool asks you to put in an URL to a page and then choose a type of colorblindness to emulate on that page. Go down to the type URL box and hit Ctrl V or Cmd V to paste in the URL. In the Select box below you'll need to pick a type of color filter. The filters shown are different types of colorblindness.
The two at the top, the red-green colorblindness are the most common. So you might want to start with testing those. I'm going choose protanopia. Then click the Fetch and Filter button. The tool will load the page with different colors to simulate this kind of colorblindness. It might take a few minutes for it to load all of the images since it has to remake them. You can see that the colors and the images have changed dramatically. The red and green from the images has basically been stripped out.
This box on the right-hand side of the page allows you to choose different settings to test your page with different types of colorblindness. Let's go to the second tool now. Go to the URL www.vischeck.com/vischeck/vischeckimage.php. This is another tool for emulating different types of colorblindness, but with this tool you up load and image file to check. Go down to the image file box and click on the Browse button.
If you're following along with the exercise filed, inside the Chapter Two folder is an image named coffee. Select that image and click Open. Now you can click on the run vis check button to change this image for how it would look for this chosen type of colorblindness. Once again it will take a few moments while the tool up loads the image and changes its colors. Let's scroll down the page to see the full image.
You can see that with this type of colorblindness it's impossible to distinguish the different colors in these coffee beans. So for instance if you had a chart or another type of image where color was important and you're asking your users to choose something based on that color, it would be impossible for them to do so in those sorts of situations. The third tool that we're going to look at is at www.snook.ca/technical/color_contrast/color.html.
This tool does the same thing that the Firefox extension we downloaded earlier does. It checks the contrast between the text color and its background color. The difference between this tool and the tool, however, is that this one allows you to quickly change the colors so that if you are failing a certain color contrast test you can quickly choose a new color and see if it passes. To change the colors, scroll down to either the foreground color or the background color box. I am going to change the background color. There are three sliders to change the red, green, and blue values.
Click on the red slider and move it to the left. You'll see in the results box to the right the calculated brightness difference and color difference, and then whether or not these values are compliant. It will either say yes, no, or sort of. Sort of means that it only passes one of the two tests. Ideally, you would want it to say yes. So let's keep moving the slider to the left. Now it says no. So we definitely want to change these colors. Going all the way to the left has just made it worse. Let's slide this back to the right.
We now have a value of yes, meaning we pass the color contrast test. The last tool is a readability test. It's online at juicystudio.com/services/readability.php. If you scroll a little ways down the page you'll see a form labeled test the readability of a web site. Here you can put in a URL and click the Calculate Readability button to have the tool measure how easy it is to read and understand the text on the page. Click inside the box, and once again hit Ctrl V or Cmd V to paste in the same URL that we used earlier.
Then click on Calculate Readability. A report will come up showing you information about the text on the page you just checked. The three rows at the bottom of the table are the names of three tests. The Gunning Fog index and Flesh Kincaid Grade. Both assign you a number that corresponds with the grade level that this would be appropriate reading for. The flesh reading this under is between 1 and 100. Generally, you want to get a value between 60 and 70. So it looks like this page will be easy to read for a number of people. These are just a few online tools that you can bookmark and use for testing.
Next we'll look at some other tools online that give you a more comprehensive analysis of the accessibility of your pages.
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