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WCAG 2 Test Rules

For developers of evaluation tools and test methodologies

About WCAG 2 Test Rules

Proposed HTML graphics contain no text

Description

This rule checks that images of text are not used

Applicability

This rule applies to any rendered image resources in a web page.

Expectation

For each test target, at least one of the following is true:

Assumptions

Accessibility Support

No accessibility support issues known.

Background

This rule is designed specifically for SC 1.4.5 Images of Text which includes exceptions to the images it applies to that are not part of SC 1.4.9 Images of Text (No Exception). Therefore, some images that are inapplicable for this rule can be applicable to SC 1.4.9 Images of Text (No Exception).

Bibliography

Accessibility Requirements Mapping

Input Aspects

The following aspects are required in using this rule.

Test Cases

Passed

Passed Example 1

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This image resource referenced by the img element does not contain text.

<img src="/test-assets/shared/fireworks.jpg" alt="fireworks going off behind the Eiffel tower at night" />

Passed Example 2

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This image resource referenced by the input element does not contain text.

<input type="image" src="/test-assets/shared/file.svg" alt="New file" />

Passed Example 3

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This image resource referenced by the svg element does not contain text.

<svg width="2in" height="3in" xmlns="http://www.w3.org/2000/svg">
	<image x="20" y="20" width="200px" height="100px" href="/test-assets/shared/fireworks.jpg">
		<title>Fireworks in Paris</title>
	</image>
</svg>

Passed Example 4

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This image resource referenced by the object element contains text, but it is not the most significant content.

<object data="/test-assets/0va7u6/times_square.jpg" title="Picture of Times Square, New York"></object>

Passed Example 5

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This image resource referenced by the img element contains text, but its presentation is essential to convey the information.

<p>
	The following image is a close up of the cover of a Classic Comics book titled "Ivanhoe" illustrating a font that
	looks like an old Gothic style font.
</p>
<img
	src="/test-assets/0va7u6/ivanhoe.png"
	alt="The word Ivanhoe written in a style that resembles old medieval letters. The letter I is colored to resemble copper. The remaining letters are black. The background is yellow."
/>

Passed Example 6

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This image resource referenced by the background-image property of the div element contains a logo with text. Logotypes are considered an essential exception.

<div
	role="img"
	aria-label="W3C logo"
	style="
    width: 100px;
    height: 100px;
    background-image: url(/test-assets/shared/w3c-logo.png);
    background-repeat: no-repeat;
  "
></div>

Passed Example 7

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This image resource referenced by the img element is an image of text (the book covers), but it is just meant to decorate the webpage of a book store, therefore it is purely decorative.

<img src="/test-assets/0va7u6/books.jpg" alt="" />
<p>Welcome to my book store</p>

Passed Example 8

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These image resources referenced by the input elements are images of text (the letter “A”), but they are not expressing anything in a human language. The image is only used to indicate how the font size can be controlled.

<input
	type="image"
	src="/test-assets/0va7u6/smallA.png"
	style="border: 1px solid black;"
	width="50px"
	height="50px"
	alt="Decrease text size"
/>
<input
	type="image"
	src="/test-assets/0va7u6/bigA.png"
	style="border: 1px solid black;"
	width="50px"
	height="50px"
	alt="Increase text size"
/>

Failed

Failed Example 1

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This image resource referenced by the img element contains text for which the particular presentation is not essential.

<img
	src="/test-assets/0va7u6/textimage.jpg"
	alt="The Accessibility Conformance Testing (ACT) Rules Format 1.0 defines a format for writing accessibility test rules."
/>

Failed Example 2

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This image resource referenced by the input element in the Image Button contains text for which the particular presentation is not essential.

<input type="image" src="/test-assets/0va7u6/button.jpg" alt="Press me" />

Failed Example 3

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This image resource referenced by the background-image property of the div element contains text for which the particular presentation is not essential.

<div style="background-image: url(/test-assets/0va7u6/textimage.jpg); width: 500px; height: 200px;" />

Failed Example 4

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This image resource referenced by the img element contains text that provides redundant information, but it still is information, therefore it is not purely decorative.

<img src="/test-assets/0va7u6/welcome.png" alt="" />
<p>Welcome to our website</p>

Inapplicable

Inapplicable Example 1

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The resource referenced by the object element does not have visible pixels.

<object date="/test-assets/0va7u6/textimage.jpg" style="display: none"></object>

Inapplicable Example 2

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This svg element does not have image element descendants.

<svg xmlns="http://www.w3.org/2000/svg">
	<text x="20" y="35">My</text>
	<text x="45" y="35">cat</text>
	<text x="55" y="55">is</text>
	<text x="70" y="55">Grumpy!</text>
</svg>

Glossary

Attribute value

The attribute value of a content attribute set on an HTML element is the value that the attribute gets after being parsed and computed according to specifications. It may differ from the value that is actually written in the HTML code due to trimming whitespace or non-digits characters, default values, or case-insensitivity.

Some notable case of attribute value, among others:

This list is not exhaustive, and only serves as an illustration for some of the most common cases.

The attribute value of an IDL attribute is the value returned on getting it. Note that when an IDL attribute reflects a content attribute, they have the same attribute value.

Embedded Image

An element presents an embedded image when any of the following is true:

Outcome

An outcome is a conclusion that comes from evaluating an ACT Rule on a test subject or one of its constituent test target. An outcome can be one of the three following types:

Note: A rule has one passed or failed outcome for every test target. When there are no test targets the rule has one inapplicable outcome. This means that each test subject will have one or more outcomes.

Note: Implementations using the EARL10-Schema can express the outcome with the outcome property. In addition to passed, failed and inapplicable, EARL 1.0 also defined an incomplete outcome. While this cannot be the outcome of an ACT Rule when applied in its entirety, it often happens that rules are only partially evaluated. For example, when applicability was automated, but the expectations have to be evaluated manually. Such “interim” results can be expressed with the incomplete outcome.

Rendered Image Resource

A rendered image resource in a web page is any resource with visible pixels that has been specified in the list of image sources of an embedded image.

Visible

Content perceivable through sight.

Content is considered visible if making it fully transparent would result in a difference in the pixels rendered for any part of the document that is currently within the viewport or can be brought into the viewport via scrolling.

Content is defined in WCAG.

For more details, see examples of visible.

Web page (HTML)

An HTML web page is the set of all fully active documents which share the same top-level browsing context.

Note: Nesting of browsing context mostly happens with iframe and object. Thus a web page will most of the time be a “top-level” document and all its iframe and object (recursively).

Note: Web pages as defined by WCAG are not restricted to the HTML technology but can also include, e.g., PDF or DOCX documents.

Note: Although web pages as defined here are sets of documents (and do not contain other kind of nodes), one can abusively write that any node is “in a web page” if it is a shadow-including descendant of a document that is part of that web page.

Implementations

There are currently no known implementations for this rule. If you would like to contribute an implementation, please read the ACT Implementations page for details.

Changelog

This is the first version of this ACT rule.

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This is an unpublished draft preview that might include content that is not yet approved. The published website is at w3.org/WAI/.