hasBlendModes()

in src/core/evaluator.js [277:387]

• 93 lines of code
• 32 McCabe index (conditional complexity)

  hasBlendModes(resources, nonBlendModesSet) {
    if (!(resources instanceof Dict)) {
      return false;
    }
    if (resources.objId && nonBlendModesSet.has(resources.objId)) {
      return false;
    }

    const processed = new RefSet(nonBlendModesSet);
    if (resources.objId) {
      processed.put(resources.objId);
    }

    const nodes = [resources],
      xref = this.xref;
    while (nodes.length) {
      const node = nodes.shift();
      // First check the current resources for blend modes.
      const graphicStates = node.get("ExtGState");
      if (graphicStates instanceof Dict) {
        for (let graphicState of graphicStates.getRawValues()) {
          if (graphicState instanceof Ref) {
            if (processed.has(graphicState)) {
              continue; // The ExtGState has already been processed.
            }
            try {
              graphicState = xref.fetch(graphicState);
            } catch (ex) {
              // Avoid parsing a corrupt ExtGState more than once.
              processed.put(graphicState);

              info(`hasBlendModes - ignoring ExtGState: "${ex}".`);
              continue;
            }
          }
          if (!(graphicState instanceof Dict)) {
            continue;
          }
          if (graphicState.objId) {
            processed.put(graphicState.objId);
          }

          const bm = graphicState.get("BM");
          if (bm instanceof Name) {
            if (bm.name !== "Normal") {
              return true;
            }
            continue;
          }
          if (bm !== undefined && Array.isArray(bm)) {
            for (const element of bm) {
              if (element instanceof Name && element.name !== "Normal") {
                return true;
              }
            }
          }
        }
      }
      // Descend into the XObjects to look for more resources and blend modes.
      const xObjects = node.get("XObject");
      if (!(xObjects instanceof Dict)) {
        continue;
      }
      for (let xObject of xObjects.getRawValues()) {
        if (xObject instanceof Ref) {
          if (processed.has(xObject)) {
            // The XObject has already been processed, and by avoiding a
            // redundant `xref.fetch` we can *significantly* reduce the load
            // time for badly generated PDF files (fixes issue6961.pdf).
            continue;
          }
          try {
            xObject = xref.fetch(xObject);
          } catch (ex) {
            // Avoid parsing a corrupt XObject more than once.
            processed.put(xObject);

            info(`hasBlendModes - ignoring XObject: "${ex}".`);
            continue;
          }
        }
        if (!(xObject instanceof BaseStream)) {
          continue;
        }
        if (xObject.dict.objId) {
          processed.put(xObject.dict.objId);
        }
        const xResources = xObject.dict.get("Resources");
        if (!(xResources instanceof Dict)) {
          continue;
        }
        // Checking objId to detect an infinite loop.
        if (xResources.objId && processed.has(xResources.objId)) {
          continue;
        }

        nodes.push(xResources);
        if (xResources.objId) {
          processed.put(xResources.objId);
        }
      }
    }

    // When no blend modes exist, there's no need re-fetch/re-parse any of the
    // processed `Ref`s again for subsequent pages. This helps reduce redundant
    // `XRef.fetch` calls for some documents (e.g. issue6961.pdf).
    for (const ref of processed) {
      nonBlendModesSet.put(ref);
    }
    return false;
  }