Accessibility: Use ImageObject caption property as ALT text for remote embeds

[tholub]

Describe the Feature

When embedding an image from a remote site (such as the featured image from a WordPress post), the image may be presented as an ImageObject. The ImageObject schema does not include a specific property for ALT text. If ALT text exists for the image on the remote site, the ImageObject may present the ALT text in the caption property.

If no source for ALT text is found, the value of the caption property should be used as the ALT text for the embedded image.

Example featured image section from a WordPress post:

Post schema section as text: <script type="application/ld+json" class="yoast-schema-graph">{"@context":"https://schema.org","@graph":[{"@type":"WebPage","@id":"https://inl.org/1998/11/day-1-sf-to-santa-cruz/","url":"https://inl.org/1998/11/day-1-sf-to-santa-cruz/","name":"Day 1: SF to Santa Cruz - Tom&#039;s stuff","isPartOf":{"@id":"https://inl.org/#website"},"primaryImageOfPage":{"@id":"https://inl.org/1998/11/day-1-sf-to-santa-cruz/#primaryimage"},"image":{"@id":"https://inl.org/1998/11/day-1-sf-to-santa-cruz/#primaryimage"},"thumbnailUrl":"https://inl.org/wp-content/uploads/sites/3/2024/11/27908_05.sfw-3.jpg","datePublished":"1998-11-01T19:31:00+00:00","dateModified":"2024-11-18T17:44:35+00:00","author":{"@id":"https://inl.org/#/schema/person/2147ceda83fd3e40fa2c2cde2e467d79"},"breadcrumb":{"@id":"https://inl.org/1998/11/day-1-sf-to-santa-cruz/#breadcrumb"},"inLanguage":"en-US","potentialAction":[{"@type":"ReadAction","target":["https://inl.org/1998/11/day-1-sf-to-santa-cruz/"]}]},{"@type":"ImageObject","inLanguage":"en-US","@id":"https://inl.org/1998/11/day-1-sf-to-santa-cruz/#primaryimage","url":"https://inl.org/wp-content/uploads/sites/3/2024/11/27908_05.sfw-3.jpg","contentUrl":"https://inl.org/wp-content/uploads/sites/3/2024/11/27908_05.sfw-3.jpg","width":1200,"height":841,"caption":"A harvested field in the foreground gives way to an ocean under a cloudy sky. In the distance, a lighthouse can be seen on the end of a point."},{"@type":"BreadcrumbList","@id":"https://inl.org/1998/11/day-1-sf-to-santa-cruz/#breadcrumb","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://inl.org/"},{"@type":"ListItem","position":2,"name":"Blog","item":"https://inl.org/blog/"},{"@type":"ListItem","position":3,"name":"Day 1: SF to Santa Cruz"}]},{"@type":"WebSite","@id":"https://inl.org/#website","url":"https://inl.org/","name":"Tom&#039;s stuff","description":"Tom Holub&#039;s web stuff","potentialAction":[{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://inl.org/?s={search_term_string}"},"query-input":{"@type":"PropertyValueSpecification","valueRequired":true,"valueName":"search_term_string"}}],"inLanguage":"en-US"},{"@type":"Person","@id":"https://inl.org/#/schema/person/2147ceda83fd3e40fa2c2cde2e467d79","name":"tom","image":{"@type":"ImageObject","inLanguage":"en-US","@id":"https://inl.org/#/schema/person/image/","url":"https://secure.gravatar.com/avatar/2148aecfd4521da5be7788966f8e2ad3?s=96&d=mm&r=g","contentUrl":"https://secure.gravatar.com/avatar/2148aecfd4521da5be7788966f8e2ad3?s=96&d=mm&r=g","caption":"tom"},"url":"https://inl.org/author/tom/"}]}</script>

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Describe Alternatives

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Additional Context

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