Draw page content only if not empty

@@ -9,6 +9,7 @@
 - Improve verbose output
 - Import already defined form
 - Add support for deleted objects
+- Draw page content only if not empty
 
 ## 3.9.0
 

@@ -123,6 +123,9 @@ class PdfGraphics {
   /// Default font if none selected
   PdfFont? get defaultFont => _page.getDefaultFont();
 
+  bool _altered = false;
+  bool get altered => _altered;
+
   /// Draw a surface on the previously defined shape
   /// set evenOdd to false to use the nonzero winding number rule to determine the region to fill and to true to use the even-odd rule to determine the region to fill
   void fillPath({bool evenOdd = false}) {
@@ -136,6 +139,7 @@ class PdfGraphics {
     }());
 
     _buf.putString('f${evenOdd ? '*' : ''} ');
+    _altered = true;
 
     assert(() {
       if (_page.pdfDocument.verbose) {
@@ -158,6 +162,7 @@ class PdfGraphics {
     }());
 
     _buf.putString('${close ? 's' : 'S'} ');
+    _altered = true;
 
     assert(() {
       if (_page.pdfDocument.verbose) {
@@ -178,6 +183,7 @@ class PdfGraphics {
     }());
 
     _buf.putString('h ');
+    _altered = true;
 
     assert(() {
       if (_page.pdfDocument.verbose) {
@@ -224,6 +230,7 @@ class PdfGraphics {
     }());
 
     _buf.putString('${close ? 'b' : 'B'}${evenOdd ? '*' : ''} ');
+    _altered = true;
 
     assert(() {
       if (_page.pdfDocument.verbose) {
@@ -248,6 +255,7 @@ class PdfGraphics {
     // The shader needs to be registered in the page resources
     _page.addShader(shader);
     _buf.putString('${shader.name} sh ');
+    _altered = true;
 
     assert(() {
       if (_page.pdfDocument.verbose) {
@@ -354,7 +362,7 @@ class PdfGraphics {
     }
 
     _buf.putString(' cm ${img.name} Do Q ');
-  }
+    _altered = true;
 
     assert(() {
       if (_page.pdfDocument.verbose) {
@@ -571,6 +579,7 @@ class PdfGraphics {
       return true;
     }());
 
+    _altered = true;
   }
 
   void reset() {

@@ -20,6 +20,7 @@ import '../graphics.dart';
 import '../page_format.dart';
 import 'annotation.dart';
 import 'graphic_stream.dart';
+import 'object.dart';
 import 'object_dict.dart';
 import 'object_stream.dart';
 
@@ -64,11 +65,13 @@ class PdfPage extends PdfObjectDict with PdfGraphicStream {
   PdfPageRotation rotate;
 
   /// This holds the contents of the page.
-  final contents = <PdfObjectStream>[];
+  final contents = <PdfObject>[];
 
   /// This holds any Annotations contained within this page.
   final annotations = <PdfAnnot>[];
 
+  final _contentGraphics = <PdfObject, PdfGraphics>{};
+
   /// This returns a [PdfGraphics] object, which can then be used to render
   /// on to this page. If a previous [PdfGraphics] object was used, this object
   /// is appended to the page, and will be drawn over the top of any previous
@@ -76,6 +79,7 @@ class PdfPage extends PdfObjectDict with PdfGraphicStream {
   PdfGraphics getGraphics() {
     final stream = PdfObjectStream(pdfDocument);
     final g = PdfGraphics(this, stream.buf);
+    _contentGraphics[stream] = g;
     contents.add(stream);
     return g;
   }
@@ -100,8 +104,15 @@ class PdfPage extends PdfObjectDict with PdfGraphicStream {
     params['/MediaBox'] =
         PdfArray.fromNum(<double>[0, 0, pageFormat.width, pageFormat.height]);
 
+    for (final content in contents) {
+      if (!_contentGraphics[content]!.altered) {
+        content.inUse = false;
+      }
+    }
+
     // The graphic operations to draw the page
-    final contentList = PdfArray.fromObjects(contents);
+    final contentList =
+        PdfArray.fromObjects(contents.where((e) => e.inUse).toList());
 
     if (params.containsKey('/Contents')) {
       final prevContent = params['/Contents']!;
@@ -124,9 +135,10 @@ class PdfPage extends PdfObjectDict with PdfGraphicStream {
     // The /Annots object
     if (annotations.isNotEmpty) {
       if (params.containsKey('/Annots')) {
-        final annotsList = params['/Annots'];
-        if (annotsList is PdfArray) {
-          annotsList.values.addAll(PdfArray.fromObjects(annotations).values);
+        final annotationList = params['/Annots'];
+        if (annotationList is PdfArray) {
+          annotationList.values
+              .addAll(PdfArray.fromObjects(annotations).values);
         }
       } else {
         params['/Annots'] = PdfArray.fromObjects(annotations);