[x3d-public] [x3d] Comment on Specification: descriptive text for image textures

[Don Brutzman]

On 8/8/2015 9:48 AM, Spec Feedback wrote:
> Comment on 19775-1: Abstract X3D Definitions - V3.3
> http://www.web3d.org/documents/specifications/19775-1/V3.3/Part01/components/texturing.html#X3DTexture2DNode
>
> -----------------
> Summary: descriptive text for image textures
>
> X3D has a 'description' field for MovieTexture and various sensor nodes.  No
> similar description field if found for 2D texture images.  This is an
> important feature for authors to convey the intent or content of an image
> included in a scene to end users.
>
> For consistency, recommend adding a matching description field to
> X3DTexture2DNode, consistent with MovieTexture and other nodes:
>
> ================
> 18.3.3 X3DTexture2DNode
>
> X3DTexture2DNode : X3DTextureNode {
>     SFNode [in,out] metadata          NULL [X3DMetadataObject]
>     SFString [in,out] description       ""
>     SFBool []       repeatS           TRUE
>     SFBool []       repeatT           TRUE
>     SFNode []       textureProperties NULL [TextureProperties]
> }
>
> This abstract node type is the base type for all node types which specify 2D
> sources for texture images.
> ================
>
> Further considerations:
> - The description field ought to be identically included in 7.3.7
> X3DSensorNode so that guidance is consistent for all usages.
> - Further consideration is appropriate to align X3D functionality identically
> with HTML5 Recommendation guidance for text alternatives in images.
> -----------------
>
> Submitted on Saturday, 2015,  August 8 - 9:48am
> by brutzman (brutzman )
> IP: 205.155.65.226
>
> See: http://www.web3d.org/node/1694/submission/641

This is an important topic that can benefit from group discussion.

Additional reference information follows from HTML5 Recommendation.
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Text alternative
http://www.w3.org/TR/WCAG20/#text-altdef

>     Text that is programmatically associated with non-text content or referred to from text that is programmatically associated with non-text content. Programmatically associated text is text whose location can be programmatically determined from the non-text content.
>
>     Example: An image of a chart is described in text in the paragraph after the chart. The short text alternative for the chart indicates that a description follows.
>
>     Note: Refer to Understanding Text Alternatives for more information.
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Understanding Text Alternatives
http://www.w3.org/TR/UNDERSTANDING-WCAG20/conformance.html#uc-text-alternatives-head

> A text alternative is text that is used in place of non-text content for those who cannot view the non-text content. Non-text content includes such things as pictures, charts, applets, audio files, etc. People who cannot see for example would not be able to see information presented in a picture or chart. A text alternative is therefore provided that allows the user to be able to convert the information (the text) into speech. In the future, having the information in text also makes it possible to translate the information into sign language, into pictures, or into a simpler form of writing.
>
> In order for people with disabilities to be able to use this text - the text must be "programmatically determinable." This means that the text must be able to be read and used by the assistive technologies (and the accessibility features in browsers) that people with disabilities use.
>
> It must also be possible for people using assistive technologies to find these text alternatives when they encounter non-text content that they cannot use. To accomplish this, we say that the text must be "programmatically associated" with the non-text content. This means that the user must be able to use their assistive technology to find the alternative text (that they can use) when they land on the non-text content (that they can't use).

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4.7.1.1 Requirements for providing text to act as an alternative for images
http://www.w3.org/TR/html5/embedded-content-0.html#alt

> Text alternatives, [WCAG] are a primary way of making visual information accessible, because they can be rendered through any sensory modality (for example, visual, auditory or tactile) to match the needs of the user. Providing text alternatives allows the information to be rendered in a variety of ways by a variety of user agents. For example, a person who cannot see a picture can have the text alternative read aloud using synthesized speech.
>
> The alt attribute on images is a very important accessibility attribute. Authoring useful alt attribute content requires the author to carefully consider the context in which the image appears and the function that image may have in that context. The guidance included here addresses the most common ways authors use images. Additional guidance and techniques are available in Resources on Alternative Text for Images.
> 4.7.1.1.1 Examples of scenarios where users benefit from text alternatives for images
>
> They have a very slow connection and are browsing with images disabled.
> They have a vision impairment and use text to speech software.
> They have a cognitive impairment and use text to speech software.
> They are using a text-only browser.
> They are listening to the page being read out by a voice Web browser.
> They have images disabled to save on download costs.
> They have problems loading images or the source of an image is wrong.
>
> 4.7.1.1.2 General guidelines
>
> Except where otherwise specified, the alt attribute must be specified and its value must not be empty; the value must be an appropriate functional replacement for the image. The specific requirements for the alt attribute content depend on the image's function in the page, as described in the following sections.
>
> To determine an appropriate text alternative it is important to think about why an image is being included in a page. What is its purpose? Thinking like this will help you to understand what is important about the image for the intended audience. Every image has a reason for being on a page, because it provides useful information, performs a function, labels an interactive element, enhances aesthetics or is purely decorative. Therefore, knowing what the image is for, makes writing an appropriate text alternative easier.

[... Extensive specific examples are provided.]
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all the best, Don
-- 
Don Brutzman  Naval Postgraduate School, Code USW/Br       brutzman at nps.edu
Watkins 270,  MOVES Institute, Monterey CA 93943-5000 USA   +1.831.656.2149
X3D graphics, virtual worlds, navy robotics http://faculty.nps.edu/brutzman