- From: RUST Randal <RRust@COVANSYS.com>
- Date: Fri, 18 Jan 2002 10:10:04 -0500
- To: w3c-wai-ig@w3.org
Apparently there is some confusion about one of my earlier comments. I made the following statement: "Therefore, I could use the CSS background property for the inclusion of ALL non-essential elements, and then I would not have to use the "alt" tag. A blind user gets the same ESSENTIAL CONTENT as the user who can see the page." What I meant by "non-essential elements" was IMAGES, not text. Maybe that clears it up a bit. -----Original Message----- From: RUST Randal [mailto:RRust@COVANSYS.com] Sent: Friday, January 18, 2002 9:59 AM To: w3c-wai-ig@w3.org Subject: RE: WA - background-image in CSS Charles is MAKING MY POINT EXACTLY. If I have an image that I, as the author of the page, deem does NOT CONVEY CRITICAL INFORMATION, such as a picture of trees, then I SHOULD FEEL FREE TO USE IT AS A BACKGROUND IMAGE. If IT IS IMPORTANT, such as a map, then OBVIOUSLY I will include it in the HTML, and properly apply the necessary attributes for accessibility. That what I said in my very first post. -----Original Message----- From: Charles McCathieNevile [mailto:charles@w3.org] Sent: Friday, January 18, 2002 9:37 AM To: Access Systems Cc: w3c-wai-ig@w3.org Subject: Re: WA - background-image in CSS Well, there are two ways of looking at this. On one side, it is important for accessibility to convey the essential information - a page often contains lots of supplementary stuff to highlight and reinforce its message(s), and a user can find out those are there and look them up if they have an appropriate browser. In some cases part of that information will be in an inaccessible form. In the real world there is then a tension between whether someone provides more new information that they consider it important to convey, or whether they render existing information more accessible. In order to meet WCAG, there is a requirement that the background image (as part of the style) not convey critical information that is not otherwise available. That requirement makes sense. In text form, alt="" (in otherwords a null statement) is therefore an acceptable equivalent, for the purpose of meeting checkpoint 1.1. In fact with the background image there is no easy wayt to include alt information, or a description. That doesn't mean there is no way of doing it at all. If people are aware of how the Web works well - i.e. things don't appear in multiple places, they have an identifier (URI) that can be used to find them, and local services can cache the content of that identifier for speed or offline work (browsers do this automatically to a large extent, and there are ways of doing it on a wider scale), there is more that can be done. It is possible to find out what the background image is - at worst by inspecting source, although some browsers give direct access, and more tools could be made that do so - at least as far as having a URI to be ableto look at it. Then all that is required is that there is a way of getting information about the image. Some approaches from W3C spring to mind... Annotea: Annotea is a service that allows anyone to annotate anything with a URI - a page, part of a page, an image, an image as used in a particular page, etc. The annotation can be anything else on the Web - another page, a bit of text written for it, another image, and it has a type - comment, example, test, seeAlso, ... There are tools to use this in Amaya, Mozilla, Internet explorer, any javascript capable browser. It is also possible to do it from non-script-capable browsers via a Web interface. Details of Annotea are at http://www.w3.org/2001/Annotea RDFPic RDFPic is an example of a tool that incorporates information directly in an image - the open source demo tool does it for jpeg images, and allows you to save the image (using HTTP PUT - a standard that is sadly still not widely-enough implemented) including the information. The Jigsaw server (for which the demo was written) allows you to retrieve the information instead of the image, or it can be extracted from the image itself with a bit of a hack. More about RDFPic at http://www.w3.org/TR/photo-rdf which includes links to online demos SVG A lot of browsers don't yet handle SVG. On the other hand we are only talking about a background image, so that may not trouble some people. In SVG including a descriptionis trivial - consider the following two images: <?xml version="1.0" standalone="no"?> <!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 20010904//EN" "http://www.w3.org/TR/2001/REC-SVG-20010904/DTD/svg10.dtd"> <svg width="100%" height="100%" xmlns="http://www.w3.org/2000/svg"> <desc>A washed out background colour with spots on it</desc> <image xlink:href="http://example.com/spots.png" width="100%" height="100%"/> </svg> (which shows how to use a bitmap image within an SVG) or <?xml version="1.0" standalone="no"?> <!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 20010904//EN" "http://www.w3.org/TR/2001/REC-SVG-20010904/DTD/svg10.dtd"> <svg width="8cm" height="4cm" viewBox="0 0 800 400" xmlns="http://www.w3.org/2000/svg"> <desc>A colour gradient - red on the left blending to yellow on the right</desc> <g> <defs> <linearGradient id="MyGradient"> <stop offset="5%" stop-color="#F60" /> <stop offset="95%" stop-color="#FF6" /> </linearGradient> </defs> <rect fill="url(#MyGradient)" width="800" height="400"/> </g> </svg> Which is a complete image in itself - compressed this uses a very small number of bytes indeed. Both images above include a description, which can be easily extracted. There are other image annotation systems available of course, which can do the same kinds of things as RDFPic or annotea via a Web Query: as an example see http://swordfish.rdfweb.org/discovery/2001/08/codepict/ (an implementation designed for collecting pictures of multiple people, and thus finding out who has been in the same place as whom, ...) cheers Charles On Fri, 18 Jan 2002, Access Systems wrote: On Fri, 18 Jan 2002, RUST Randal wrote: my opinion only ! (well maybe not just me but I do not speak for others) > blind user gets the same ESSENTIAL CONTENT as the user who can see the page. users with disabilities or other reasons for using alternative screen display DESERVE AND ARE ENTITLED TO ALL THE CONTENT, who are "you" to determine what is "essential" content to me THIS IS ONE of the major complaints of almost all people with disabilities in all areas of access. NO ONE!, period, has the right to determine my needs and priorities. Bob *you and me as used is generic and not intended to mean any one individual ** really one of my major peeves! *** shouting is intentional and needed ASCII Ribbon Campaign accessBob NO HTML/PDF/RTF in e-mail accessys@smartnospam.net NO MSWord docs in e-mail Access Systems, engineers NO attachments in e-mail, *LINUX powered* access is a civil right *#*#*#*#*#*#*#*#*#*#*#*#*#*#*#*#*#*#*#*#*#*#*#*#*#*#*#*#*#*#*#*#*#*#*#*#*#*# *# THIS message and any attachments are CONFIDENTIAL and may be privileged. They are intended ONLY for the individual or entity named above. If you are not the intended recipient, Please notify the sender as soon as possible. Please DO NOT READ, COPY, USE, or DISCLOSE this communication to others and DELETE it from your computer systems. Thanks -- Charles McCathieNevile http://www.w3.org/People/Charles phone: +61 409 134 136 W3C Web Accessibility Initiative http://www.w3.org/WAI fax: +1 617 258 5999 Location: 21 Mitchell street FOOTSCRAY Vic 3011, Australia (or W3C INRIA, Route des Lucioles, BP 93, 06902 Sophia Antipolis Cedex, France)
Received on Friday, 18 January 2002 10:08:27 UTC