Media convergence

Current baseline

The content image hook, numbered fig, cards, and galleries resolve local page resources, section resources, global assets, static files, and explicit remote URLs through content/image-resolve.html. Raster resources can contribute intrinsic dimensions and processing derivatives. HTML Zoom eligibility is marked with data-td-image-zoom; the build-time detector only checks that theme-emitted marker.

Standalone Markdown images can already combine caption or Book numbering with processing and a link. Numbered image figures share td-figure and td-book-figure semantics. Landing media passes the shared URL trust policy, while featured images intentionally use a ranking resolver because their job is to select a representative image rather than render one explicit source.

Remaining problem

The shared safety boundary is stronger than the shared media model. Landing media still does not obtain the same page-resource metadata and processing result as body images. Featured-image selection and explicit image resolution have separate result shapes. Some compatibility class names remain in markup, and Book’s full fig form cannot express every processing option available to the native image hook.

The design question is therefore no longer “replace seven image entry points.” It is whether the remaining surfaces can share a small result contract without erasing their different semantics.

Goals and non-goals

Goals:

• define one normalized media-result shape for URL, source URL, dimensions, alternative text, attribution, processability, and external status;
• let explicit content images, Landing media, and representative images reuse that shape where their source semantics overlap;
• keep figure markup and Zoom eligibility single-owned;
• decide whether the full fig form needs processing or whether authors should use the native image form for processed numbered images;
• retire compatibility markup only after consumer evidence and a release note.

Non-goals:

• adding a third-party lightbox or remote image service;
• changing image Zoom from opt-in to site policy by accident;
• giving galleries a new caption, sequence, or carousel model;
• merging non-image Book targets such as tables, equations, and examples into an image-only base class;
• making featured-image ranking identical to explicit image resolution.

Proposed phases

M1 — Result contract

Document the fields returned by the content and representative-image resolvers, then extract the intersection into one internal media-result contract. Keep source ranking in the featured resolver and source resolution in the content resolver. This is an internal refactor with byte-stable output.

M2 — Landing resource metadata

Allow Landing items to resolve eligible local resources through the media contract, gaining intrinsic dimensions and the same URL/security decision. Explicit width and height in Landing data continue to win. Remote and static sources remain valid but cannot pretend to have processable-resource metadata.

M3 — Full figure capability decision

Choose one of two answers:

1. add processing arguments to the full fig source form and normalize them through the same processing helper; or
2. keep processing exclusively on native Markdown images and document full fig as the container for arbitrary numbered block content.

No implementation should leave both answers half-supported. Markdown/LLMS must link to the documented source or derivative consistently in both forms.

M4 — Compatibility retirement

Inventory downstream CSS and JavaScript before removing old image-element classes or attributes. If a compatibility name is still used, retain it for a documented release window or migrate the owning site in the same release train.

Safety, output, and accessibility

• Image URLs keep the shared scheme and remote-host policy.
• Missing required alternative text warns and renders a decorative fallback only where the current contract permits it.
• Width and height never claim metadata that an SVG, static file, or remote source did not provide.
• Linked images are not Zoom targets; the runtime preserves dialog focus, keyboard close, reduced motion, and narrow-screen containment.
• Print, Markdown, RSS, and LLMS strip interaction markers while retaining the intended image, caption, attribution, number, and link.

Acceptance criteria

Each phase owns byte-level HTML and Markdown evidence, content and Landing resolver tests, URL/security checks, image-processing tests, Book targets, gallery/Zoom browser tests, and real-site EN/ZH narrow-screen review. The proposal is accepted only after the M3 capability choice is explicit.

Open decisions

1. Is one shared result struct enough, or would a common lower-level URL/resource record keep resolver ownership clearer?
2. Should Landing consume resource attribution, or only dimensions and URL?
3. Does full fig processing solve a real consumer need now that native images support numbering, captions, links, and processing together?
4. Which emitted compatibility names are still used by real consumers?