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Describing complex graphics

From: Web Accessibility Principles

Video: Describing complex graphics

>> Sometimes the amount of information that an image conveys is huge, much more then is useful in an alt attribute. While there is no limit on the amount of characters you can place is an alt attribute they are usually kept very short so that screen users are not burdened by a tone of text as well as users of small screen devices with images off. Its not a good idea to place all of the data that a chart, graph or diagram is conveying in an alt attribute. Instead you can use the long desk attribute, this attribute contains a URL to another page with a longer text equivalent of the image.

Describing complex graphics

>> Sometimes the amount of information that an image conveys is huge, much more then is useful in an alt attribute. While there is no limit on the amount of characters you can place is an alt attribute they are usually kept very short so that screen users are not burdened by a tone of text as well as users of small screen devices with images off. Its not a good idea to place all of the data that a chart, graph or diagram is conveying in an alt attribute. Instead you can use the long desk attribute, this attribute contains a URL to another page with a longer text equivalent of the image.

Let's look at an example of this that has been added to the government.html page. If you're following along with the exercise files it's saved in the 0605 folder of chapter six exercise files. Scroll down the page in the design view, we have a large pie chart showing a lot of data on this page. This is important information but it wouldn't make much sense to put it all in an alt attribute. Instead create a separate simpler page with all of the data in it in a text form.

In the exercise files this page is named budgetdescription.htm, open that in Dreamweaver now. This page simply has the same data in a list. There is a heading to the list identifying what the data is and then after the data there is a link to go back to the previous page, in this case the government page. Scroll back up in design view. You'll notice that this page does not have a navigation bar on it. All it has is the logo, the data and the footer information.

This page should be simple so that a screen reader can go to it and immediately get the data from the image that they couldn't read. So how do connect that complex graphic with this simple page? Go back to government.html, click on the pie chart graphic, we need to add an alt attribute and a long desk attribute to this image. In the properties inspector click in the alt field, we'll use the alt text to alert a screen reader user that there is a longer description available, type in this field chart of budget then in parenthesis type click for data.

Now we need to add the long desk attribute so that a screen reader user can actually click on this image and go to the description open the tag inspector panel. If the general listing is open click on the dash next to it to close it, then make sure that the CSS/accessibility list is open. Click in the field beside the long desk label. You will see two icons appear to the right of this field, one to point to another file in your sight and another to browse to another file in your site.

Let's click on the file folder icon to browse to another icon in the site. The value of the long desk field should always be a page but for some reason Dreamweaver wants you to insert an image. Just ignore that it calls the dialog box that opens select image source. Browse to where you have the exercise files saved on your computer and go to the chapter six folder within the exercise files. Then go to the 06_05 folder. Because Dreamweaver thinks you are looking for an image it has files of type pre filled with image files and will not show you any HTML pages that you can choose.

So click on the files of type menu and choose all files. Now the page budget description will show for you to select, click OK. A link to the budget description file is now basically embedded in the image. A screen reader can then announce that link to its users and they have the option of following it to hear the full description. As with the title attribute it is not guaranteed that a screen reader user will hear this announcement depending on their own settings and they type of screen reader they are using.

Because of this it is best if you can add a real text link in the page that screen readers can follow to see the full description. This can also be useful to others such as people who would have a hard time processing this graphic but could deal more easily with text. They would also be able to enlarge the text if they were having trouble reading the data in the graphic, so scroll down the page in design view. At the end of the description there is a paragraph of text that shows beneath the image, click at the end of that paragraph and type view chart data as text.

Then select this text and go down to the link box in the properties inspector, click the folder icon beside the field, browse to the exercise files folder on your computer and the chapter six folder within it. Then go to the 0605 chapter and select the budget description page then click OK. Now screen reader users have two ways to get to that page, through the long desk attribute or through the regular text link and other users can also benefit from the plain text description if the date.

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This video is part of

Image for Web Accessibility Principles
Web Accessibility Principles

68 video lessons · 25805 viewers

Zoe Gillenwater
Author

 
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  1. 2m 0s
    1. Welcome
      1m 3s
    2. Using the exercise files
      57s
  2. 33m 15s
    1. What does accessibility mean?
      5m 51s
    2. How does accessibility help your users?
      3m 30s
    3. Experiencing a website via a screen reader
      5m 46s
    4. How does accessibility help you and your clients?
      3m 9s
    5. Overview of Section 508 standards
      5m 51s
    6. Overview of WCAG standards
      6m 4s
    7. Understanding consistency and semantic markup
      3m 4s
  3. 54m 31s
    1. Understanding screen readers and accessibility tools
      6m 12s
    2. Getting accessible browsers
      5m 41s
    3. Customizing Firefox for accessibility testing
      5m 53s
    4. Using custom accessibility toolbars
      5m 28s
    5. Using Fangs and the Color Contrast Analyzer
      5m 30s
    6. Accessibility tools to bookmark
      5m 53s
    7. Using automated accessibility checking tools
      4m 57s
    8. Setting up the JAWS screen reader on Windows
      6m 42s
    9. Using the VoiceOver screen reader on Mac OS X
      5m 52s
    10. Setting Dreamweaver accessibility preferences
      2m 23s
  4. 26m 12s
    1. Avoiding tables for layout
      3m 30s
    2. Using CSS for layout
      2m 40s
    3. Creating a fixed-width layout
      5m 51s
    4. Creating an elastic layout
      3m 51s
    5. Creating a liquid layout
      3m 4s
    6. Customizing a liquid layout
      7m 16s
  5. 1h 6m
    1. Specifying the language
      3m 43s
    2. Setting page titles
      2m 16s
    3. Setting headings and paragraphs
      9m 55s
    4. Styling headings
      9m 56s
    5. Hiding section headings from sighted users
      6m 41s
    6. Styling text for readability
      6m 41s
    7. Ensuring proper color contrast
      6m 36s
    8. Creating text emphasis
      4m 29s
    9. Indicating quotations
      4m 29s
    10. Creating basic lists
      4m 16s
    11. Styling lists
      7m 15s
  6. 1h 15m
    1. Using lists for navigation
      6m 45s
    2. Creating a horizontal navigation bar
      13m 25s
    3. Creating a vertical navigation bar
      11m 44s
    4. Adding skip navigation links
      12m 0s
    5. Hiding skip navigation links
      6m 17s
    6. Proper link text and title attributes
      6m 11s
    7. Opening new windows
      4m 28s
    8. Accessibility limitations of fly-out menus
      6m 30s
    9. Creating an accessible fly-out menu
      8m 38s
  7. 27m 55s
    1. Proper ALT text for navigation images
      4m 57s
    2. Proper ALT text for decorative images
      5m 19s
    3. Adding ALT text to an existing site
      6m 9s
    4. Adding ALT text to image maps
      5m 58s
    5. Describing complex graphics
      5m 32s
  8. 34m 1s
    1. Using tables for data
      3m 0s
    2. Creating header cells
      4m 5s
    3. Adding table captions and summaries
      9m 9s
    4. Styling tables
      5m 19s
    5. Applying header cells to complex tables
      6m 52s
    6. Adding id and headers attributes
      5m 36s
  9. 42m 7s
    1. Understanding form accessibility issues
      3m 7s
    2. Labeling form fields
      6m 9s
    3. Adding fieldsets and legends
      4m 42s
    4. Moving forms out of tables
      3m 44s
    5. Cleaning up a form's appearance
      4m 53s
    6. Aligning labels and fields using CSS
      9m 39s
    7. Indicating required fields
      6m 15s
    8. Dealing with CAPTCHA
      3m 38s
  10. 7m 29s
    1. The Text-Only technique
      3m 21s
    2. The Access Keys technique
      2m 35s
    3. The Tab Index technique
      1m 33s
  11. 18s
    1. Goodbye
      18s

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