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fix(pdf): validate exports before claiming conformance

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Signed-off-by: Rudy Celekli <rudy@gradiahq.com>
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Rudy Celekli committed 2026-10-07 16:39:40 -04:00
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engineering/engineering-pdf-engine-architect.md
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@@ -574,12 +574,13 @@ export const CVPageViewportScaler: React.FC<ScalerProps> = ({
### 5. Accessible Tagged PDF & PDF/A-2b Post-Processing Pipeline (`pikepdf` Python)
Applies non-destructive metadata post-processing using `pikepdf` to attach PDF/A-2b and PDF/UA-1 XMP metadata packets, enforce sRGB Output Intent, and linearize for instant web streaming:
Requires `pikepdf[pdfa] >= 10.14`. Update descriptive metadata, install a real sRGB output intent and return bytes only after the PDF/A-2b save validator accepts the written document. Metadata declarations alone do not establish conformance; this helper does not establish or declare PDF/UA-1 compliance.
```python
# pdf_post_processor.py
import io
import pikepdf
from pikepdf import pdfa
def post_process_pdf_a2b(
pdf_bytes: bytes,
@@ -587,39 +588,23 @@ def post_process_pdf_a2b(
author: str = "System",
subject: str = "Standard Report"
) -> bytes:
"""Post-process a Chromium tagged PDF into compliant PDF/A-2b and PDF/UA-1."""
pdf = pikepdf.open(io.BytesIO(pdf_bytes))
"""Return a validated PDF/A-2b candidate, or raise pdfa.PdfaError."""
with pikepdf.open(io.BytesIO(pdf_bytes)) as pdf:
with pdf.open_metadata() as meta:
meta["dc:title"] = title
meta["dc:creator"] = [author]
meta["dc:description"] = subject
# 1. Update Document Info Dictionary
with pdf.open_metadata() as meta:
meta["dc:title"] = title
meta["dc:creator"] = [author]
meta["dc:description"] = subject
meta["pdfaid:part"] = "2"
meta["pdfaid:conformance"] = "B"
meta["pdfuaid:part"] = "1"
# 2. Attach sRGB Output Intent if not present
if "/OutputIntents" not in pdf.Root:
icc_profile_data = b"..." # Embed standard sRGB2014 ICC profile stream
icc_stream = pdf.make_stream(icc_profile_data)
icc_stream["/N"] = 3
output_intent = pdf.make_indirect({
"/Type": pikepdf.Name("/OutputIntent"),
"/S": pikepdf.Name("/GTS_PDFA1"),
"/OutputConditionIdentifier": pikepdf.String("sRGB IEC61966-2.1"),
"/Info": pikepdf.String("sRGB IEC61966-2.1"),
"/DestOutputProfile": icc_stream
})
pdf.Root["/OutputIntents"] = pdf.make_array([output_intent])
# 3. Save linearized (Fast Web View)
out_buf = io.BytesIO()
pdf.save(out_buf, linearize=True)
return out_buf.getvalue()
out_buf = io.BytesIO()
# save supplies a valid built-in ICC profile, prepares metadata,
# reopens the written bytes and rejects violations or unchecked constructs.
# It does not embed missing fonts or convert page colours/content.
pdfa.save(pdf, out_buf, "2b", output_intent="sRGB", linearize=True)
return out_buf.getvalue()
```
Handle `pdfa.PdfaError` as a failed export gate, preserving its report for remediation. Fix unsupported content with an appropriate converter rather than stamping conformance identifiers onto it. Use [veraPDF](https://verapdf.org/) for authoritative PDF/A validation and a separate PDF/UA validation workflow before making accessibility claims. See [pikepdf's validation and repair contract](https://pikepdf.readthedocs.io/en/latest/topics/pdfa.html).
### 6. Automated PDF Vector & Text Integrity Auditor (Python)
Audits compiled PDF binaries to verify direct vector text operators (`Tj`, `TJ`), confirm `/ToUnicode` CMaps, verify tag structure, and detect Skia 72 DPI bitmap fallbacks:
@@ -685,7 +670,7 @@ class PDFVectorIntegrityAuditor:
- Wait for `document.fonts.ready`.
- Invoke `page.pdf({ width, height, preferCSSPageSize: true, printBackground: true, tagged: true })`.
5. **Step 5: Metadata Post-Processing & Audit Gate**:
- Pass raw PDF through `pikepdf` to attach PDF/A-2b and PDF/UA-1 XMP metadata packets.
- Pass raw PDF through the validated PDF/A-2b save gate; remediate failures and independently validate PDF/UA accessibility before claiming it.
- Execute `PDFVectorIntegrityAuditor` to confirm vector text operators and verify zero rasterization fallbacks.
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