mozilla/pdf.js · error · FormatError

Unknown PatternName: ${patternName}

Error message

Unknown PatternName: ${patternName}

What it means

FormatError thrown when a pattern referenced by name cannot be resolved at all: the name is absent from the page/resources Pattern dictionary and xref.fetchIfRef returns nothing. It means the content stream names a pattern that does not exist in the resource chain.

Source

Thrown at src/core/evaluator.js:1667

          );
        } else if (typeNum === PatternType.SHADING) {
          const shading = dict.get("Shading");
          const objId = this.parseShading({
            shading,
            resources,
            localColorSpaceCache,
            localShadingPatternCache,
          });
          if (objId) {
            const matrix = lookupMatrix(dict.getArray("Matrix"), null);
            operatorList.addOp(fn, ["Shading", objId, matrix]);
          }
          return undefined;
        }
        throw new FormatError(`Unknown PatternType: ${typeNum}`);
      }
    }
    throw new FormatError(`Unknown PatternName: ${patternName}`);
  }

  async parseMarkedContentProps(contentProperties, resources) {
    return parseMarkedContentProps(this.xref, contentProperties, resources);
  }

  async getOperatorList({
    stream,
    task,
    resources,
    operatorList,
    initialState = null,
    fallbackFontDict = null,
    prevRefs = null,
  }) {
    if (stream.isAsync) {
      const bytes = await stream.asyncGetBytes();
      if (bytes) {

View on GitHub (pinned to 5903d58d58)

Solutions

1. Enable ignoreErrors: true so the missing pattern degrades to a warning.
2. Repair the PDF: add the missing Pattern entry or fix the referenced name.
3. Verify the resources object passed to getOperatorList is the correct one for that content stream.

Example fix

// before
getDocument({ data }); // render aborts: Unknown PatternName

// after
getDocument({ data, ignoreErrors: true }); // missing pattern skipped

try {
  await page.render({ canvasContext, viewport }).promise;
} catch (e) {
  if (/Unknown PatternName/.test(e.message)) {
    await reloadWith({ ignoreErrors: true });
  } else throw e;
}

When it happens

Trigger: A setFillColorN/setStrokeColorN operator uses a /Pattern color space and names a pattern that is not present in the current resources' Pattern dict (typo, missing entry, or wrong resource scope).

Common situations: PDFs whose resource dictionaries were stripped or merged incorrectly, renamed pattern names, or content streams moved between pages without updating resources.

Related errors

• Unknown PatternType: ${typeNum}
• No shading resource found
• No shading object found
• Unable to decode inline image: "${reason}".
• getOperatorList - ignoring circular reference: ${objId}

AI-assisted analysis of mozilla/pdf.js@5903d58d58 (2026-08-13). Data as JSON: /api/errors/e48e54439a3a2938. Report an issue: GitHub.