fix #1017

fix test name

.gitignore

@@ -105,6 +105,7 @@ $tf/
 _ReSharper*/
 *.[Rr]e[Ss]harper
 *.DotSettings.user
+.idea
 
 # JustCode is a .NET coding add-in
 .JustCode

src/UglyToad.PdfPig.Tests/Writer/PdfDocumentBuilderTests.cs

@@ -780,6 +780,24 @@
             }
         }
 
+        [Fact]
+        public void CanCopyIssue1017()
+        {
+            using (var document = PdfDocument.Open(IntegrationHelpers.GetDocumentPath("_citUR2jB1_ay56u6vELzk.pdf")))
+            {
+                using (var pdfWriter = new PdfDocumentBuilder())
+                {
+                    var page = document.GetPage(1);
+                    
+                    var newPage = pdfWriter.AddPage(page.Width, page.Height);
+                    newPage.CopyFrom(page);
+                    
+                    var b = pdfWriter.Build();
+                    Assert.NotEmpty(b);
+                }
+            }
+        }
+
         [Fact]
         public void CanCopyPage()
         {

src/UglyToad.PdfPig/Writer/PdfPageBuilder.cs

@@ -974,13 +974,16 @@
 
                         gstateName = newName;
                     }
-
-                    if (!(gstate.Value is IndirectReferenceToken fontReferenceToken))
+                    
+                    // According to PDF spec 32000-1:2008, section 8.4.5, ExtGState can contain both direct values and indirect references
+                    if (gstate.Value is IndirectReferenceToken fontReferenceToken)
                     {
-                        throw new PdfDocumentFormatException($"Expected a IndirectReferenceToken for the XObject, got a {gstate.Value.GetType().Name}");
+                        pageGstateDictionary[gstateName] = documentBuilder.CopyToken(srcPage.pdfScanner, fontReferenceToken);
+                    }
+                    else
+                    {
+                        pageGstateDictionary[gstateName] = documentBuilder.CopyToken(srcPage.pdfScanner, gstate.Value);
                     }
-
-                    pageGstateDictionary[gstateName] = documentBuilder.CopyToken(srcPage.pdfScanner, fontReferenceToken);
                 }
             }