adobe-trustmark-p.png is Adobe's official images/ghost_P.png Variant P example from adobe/trustmark at commit 0ed40cbe8188f664fd9cbbeacd969807de27440a.

Source: https://raw.githubusercontent.com/adobe/trustmark/0ed40cbe8188f664fd9cbbeacd969807de27440a/images/ghost_P.png
SHA-256: e58c5825ed7e5d9fb04710ea541b61bd55879cad65554c0d46260aa24b3d0755
Expected signal: TrustMark Variant P, schema 1
License: MIT, reproduced in ../licenses/adobe-trustmark-MIT.txt

Ideogram C2PA attribution

ideogram-c2pa.png is a SYNTHETIC signed manifest, not a vendor download: a 64x64 flat PNG carrying a C2PA claim (trainedAlgorithmicMedia, claim_generator "Ideogram/3.0") signed by a throwaway test CA whose leaf certificate subject is O=Ideogram, Inc, CN=Ideogram, Inc. It exercises the issuer-to-platform ATTRIBUTION path end to end through the real reader; the signer is deliberately untrusted (no trust anchors ship), which is also the fixture's second assertion: attribution and signer trust are separate dimensions.

Expected signal: C2PA, platform Ideogram, ai_from_metadata True
Expected signer: untrusted (test CA; attribution must not imply trust)
Recipe (no keys are committed): create a CA and an ES256 leaf with digitalSignature key usage and subject CN=Ideogram, Inc, then c2pa.Builder.from_json(...).sign_file(png, out, Signer.from_info( C2paSignerInfo(b"es256", leaf_pem + ca_pem, pkcs8_key, None))).
No user upload and no Ideogram artifact contributes pixels or bytes.