Ensure that Mesh /Shadings have non-zero width/height (issue 17848)

src/core/evaluator.js

@@ -1472,26 +1472,43 @@ class PartialEvaluator {
     // Shadings and patterns may be referenced by the same name but the resource
     // dictionary could be different so we can't use the name for the cache key.
     let id = localShadingPatternCache.get(shading);
-    if (!id) {
-      var shadingFill = Pattern.parseShading(
+    if (id) {
+      return id;
+    }
+    let patternIR;
+
+    try {
+      const shadingFill = Pattern.parseShading(
         shading,
         this.xref,
         resources,
         this._pdfFunctionFactory,
         localColorSpaceCache
       );
-      const patternIR = shadingFill.getIR();
-      id = `pattern_${this.idFactory.createObjId()}`;
-      if (this.parsingType3Font) {
-        id = `${this.idFactory.getDocId()}_type3_${id}`;
+      patternIR = shadingFill.getIR();
+    } catch (reason) {
+      if (reason instanceof AbortException) {
+        return null;
       }
-      localShadingPatternCache.set(shading, id);
+      if (this.options.ignoreErrors) {
+        warn(`parseShading - ignoring shading: "${reason}".`);
 
-      if (this.parsingType3Font) {
-        this.handler.send("commonobj", [id, "Pattern", patternIR]);
-      } else {
-        this.handler.send("obj", [id, this.pageIndex, "Pattern", patternIR]);
+        localShadingPatternCache.set(shading, null);
+        return null;
       }
+      throw reason;
+    }
+
+    id = `pattern_${this.idFactory.createObjId()}`;
+    if (this.parsingType3Font) {
+      id = `${this.idFactory.getDocId()}_type3_${id}`;
+    }
+    localShadingPatternCache.set(shading, id);
+
+    if (this.parsingType3Font) {
+      this.handler.send("commonobj", [id, "Pattern", patternIR]);
+    } else {
+      this.handler.send("obj", [id, this.pageIndex, "Pattern", patternIR]);
     }
     return id;
   }
@@ -1551,14 +1568,16 @@ class PartialEvaluator {
           );
         } else if (typeNum === PatternType.SHADING) {
           const shading = dict.get("Shading");
-          const matrix = dict.getArray("Matrix");
           const objId = this.parseShading({
             shading,
             resources,
             localColorSpaceCache,
             localShadingPatternCache,
           });
-          operatorList.addOp(fn, ["Shading", objId, matrix]);
+          if (objId) {
+            const matrix = dict.getArray("Matrix");
+            operatorList.addOp(fn, ["Shading", objId, matrix]);
+          }
           return undefined;
         }
         throw new FormatError(`Unknown PatternType: ${typeNum}`);
@@ -2109,6 +2128,9 @@ class PartialEvaluator {
               localColorSpaceCache,
               localShadingPatternCache,
             });
+            if (!patternId) {
+              continue;
+            }
             args = [patternId];
             fn = OPS.shadingFill;
             break;

src/core/pattern.js

@@ -956,13 +956,20 @@ class MeshShading extends BaseShading {
   }
 
   getIR() {
+    const { bounds } = this;
+    // Ensure that the shading has non-zero width and height, to prevent errors
+    // in `pattern_helper.js` (fixes issue17848.pdf).
+    if (bounds[2] - bounds[0] === 0 || bounds[3] - bounds[1] === 0) {
+      throw new FormatError(`Invalid MeshShading bounds: [${bounds}].`);
+    }
+
     return [
       "Mesh",
       this.shadingType,
       this.coords,
       this.colors,
       this.figures,
-      this.bounds,
+      bounds,
       this.bbox,
       this.background,
     ];