Slide2-8 WCAG: Perceivable Success Criteria
Perceivable:
Information and user interface components must be presentable to users in ways they can perceive. This means that users must be able to perceive the information being presented. User agents, like screen readers, require clearly defined HTML elements within a structured web page. The Banner, Navigation panel, Main section, and Footer are visually perceivable on a standard computer screen, but not necessarily on a screen reader device.
The intent of WCAG 1.1 Text Alternatives Success Criterion is to make information conveyed by non-text content, such as images, accessible through the use of a text alternative. Text alternatives make information accessible because they can be rendered through any sensory modality. Such as visual, auditory or tactile to match the needs of the user.
A person who cannot see a picture can have the text alternative read aloud using synthesized speech.
A person who cannot hear an audio file can have the text alternative displayed for reading.
The intent of WCAG 1.2 Time Based Media Success Criterion is to make information conveyed by prerecorded audio-only and prerecorded video-only content available to all users.
A video with no audio is a silent movie, and a written descriptive video transcript will provide an equivalent to what is presented visually.
For prerecorded video content, authors have the option to provide an audio track, which will serve as an alternative equivalent to the video. This approach would not only make the video content accessible to blind users, but also make it easier for those with cognitive, language and learning disabilities to understand the content because it would provide parallel presentation.
The intent of WCAG 1.3 Adaptable Success Criterion is to ensure that information and relationships that are implied by visual or auditory formatting are preserved when the presentation format changes. Sighted users perceive structure and relationships through various visual cues. For example:
Headings are often in a larger, bold font separated from paragraphs by blank lines;
List items are preceded by a bullet and perhaps indented;
Paragraphs are separated by a blank line;
Items that share a common characteristic are organized into tabular rows and columns;
Form fields may be positioned as groups that share text labels;
A different background colour may be used to indicate that several items are related to each other;
Words that have special status are indicated by changing the font family, or bolding, italicizing or underlining them; and so on.
The intent of WCAG 1.4 Distinguishable Success Criterion is to ensure that all users can access information that is conveyed by colour or audio differences.
Playing audio automatically when landing on a page may impact screen reader users. Individuals who use screen reading software can find it hard to hear the speech output if there is other audio playing at the same time. Therefore, it is important that the user be able to turn off the background sound or control the volume level.
If the information is conveyed through colour differences in an image the colour may not be seen by users with colour deficiencies. Providing the information conveyed with colour through another visual means ensures users who cannot see colour can still perceive the information.
The intent of this Success Criterion is to provide enough contrast between text and its background so that it can be read by people with moderately low vision, who do not use contrast-enhancing assistive technology.