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Image Composition Module

Purpose

imageComposition owns versioned baked image Contents whose base raster remains immutable and whose overlays are stored as safe, validated SVG Contents. It has no Post, Group, publication, or client-specific source dependency.

Public API

  • POST /v1/user/image-compositions
  • GET /v1/user/image-compositions/:contentManifestId
  • POST /v1/user/image-compositions/:contentManifestId/revisions
  • GET /v1/user/image-compositions for catalog-placed composition summaries

Create stores standalone Content by default. An optional owned folderId uses the normal file-catalog placement flow. Resolved detail includes fileCatalogItemId only when such a placement exists.

Identity And Revisions

ImageCompositionIdentity(userId, compositionId) converges initial creates and tracks both the immutable root and current Content rows. Revisions compare and swap currentContentId; if the identity has a catalog placement, the same transaction advances that FileCatalogItem to the new Content.

Operation records provide durable idempotency and recovery without making a catalog item mandatory.

Storage And Safety

  • The baked PNG is the default renderable Content and carries the versioned semantic recipe in properties.imageComposition.
  • The base raster and validated SVG stickers are referenced through durable ContentDependency edges.
  • Client-defined SVGs are restricted to a small element and attribute allowlist. Passive text presentation values are validated per element and grammar.
  • SVGs remain deterministic and self-contained: scripts, event handlers, style blocks, CSS functions, external resources, links, filters, masks, and clip-paths are rejected.
  • Accepted SVGs are stored as raw immutable Contents with restrictive serving headers.
  • Previews are baked from the final PNG, so ordinary clients show stickers without composition-specific preview logic.

Verification

Primary coverage lives in test/imageComposition*.test.ts, including standalone creation/revision, optional catalog placement, concurrency, idempotency, dependency integrity, preview generation, and authorization.