restore original graphical state after template

lib/external.js

@@ -2,6 +2,7 @@
 
 const PDF = require('./object')
 const Parser = require('./parser/parser')
+const ops = require('./ops')
 
 const PROPERTIES_TO_COPY = {
   colorSpaces: 'ColorSpace',
@@ -106,6 +107,16 @@ module.exports = class ExternalDocument {
       throw new TypeError('External document is invalid')
     }
 
+    // Create content chunks used to save and restore the graphical state so a template cannot mess
+    // with the page's own graphical state.
+    await doc._startContentObject()
+    await doc._write(ops.q())
+    await doc._endContentObject()
+    await doc._startContentObject()
+    await doc._write(ops.Q())
+    await doc._endContentObject()
+    const [storeGraphicalState, restoreGraphicalState] = doc._contents.splice(doc._contents - 3, 2)
+
     for (const page of this._iterPagesRecursively(doc, kids, filter)) {
       // if the page object does not define its MediaBox, explicitly set its MediaBox to the
       // value defined by its parent Pages object
@@ -130,10 +141,15 @@ module.exports = class ExternalDocument {
       if (!Array.isArray(contents)) {
         contents = [contents]
       }
+      contents = [
+        storeGraphicalState._object.toReference(),
+        ...contents,
+        restoreGraphicalState._object.toReference()
+      ]
 
       let resources = first.get('Resources')
       if (resources instanceof PDF.Reference) {
-      resources = resources.object.properties
+        resources = resources.object.properties
       }
 
       doc._template = {