Create wrapWidget helper

 # Changelog
 
+## 3.3.0
+
+- Add wrapWidget helper
+
 ## 3.2.1
 
 - Add meta and image dependencies

 import 'dart:async';
 import 'dart:io';
-import 'dart:typed_data';
-import 'dart:ui' as ui;
 
 import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
@@ -9,7 +7,6 @@ import 'package:flutter/rendering.dart';
 import 'package:flutter/services.dart';
 import 'package:markdown/markdown.dart' as markdown;
 import 'package:path_provider/path_provider.dart';
-
 import 'package:pdf/pdf.dart';
 import 'package:pdf/widgets.dart' as pw;
 import 'package:printing/printing.dart';
@@ -156,21 +153,17 @@ class MyAppState extends State<MyApp> {
   }
 
   Future<void> _printScreen() async {
-    final RenderRepaintBoundary boundary =
-        previewContainer.currentContext.findRenderObject();
-    final ui.Image im = await boundary.toImage();
-    final ByteData bytes =
-        await im.toByteData(format: ui.ImageByteFormat.rawRgba);
-    print('Print Screen ${im.width}x${im.height} ...');
-
     final bool result =
-        await Printing.layoutPdf(onLayout: (PdfPageFormat format) {
+        await Printing.layoutPdf(onLayout: (PdfPageFormat format) async {
       final pw.Document document = pw.Document();
 
-      final PdfImage image = PdfImage(document.document,
-          image: bytes.buffer.asUint8List(),
-          width: im.width,
-          height: im.height);
+      final PdfImage image = await wrapWidget(
+        document.document,
+        key: previewContainer,
+        pixelRatio: 2.0,
+      );
+
+      print('Print Screen ${image.width}x${image.height}...');
 
       document.addPage(pw.Page(
           pageFormat: format,

@@ -20,3 +20,4 @@ export 'src/printer.dart';
 export 'src/printing.dart';
 export 'src/printing_info.dart';
 export 'src/raster.dart';
+export 'src/widget_wrapper.dart';

+/*
+ * Copyright (C) 2017, David PHAM-VAN <dev.nfet.net@gmail.com>
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import 'dart:async';
+import 'dart:typed_data';
+import 'dart:ui' as ui;
+
+import 'package:flutter/material.dart';
+import 'package:flutter/rendering.dart';
+import 'package:pdf/pdf.dart';
+
+/// Wrap a Flutter Widget identified by a GlobalKey to a PdfImage.
+Future<PdfImage> wrapWidget(
+  PdfDocument document, {
+  @required GlobalKey key,
+  int width,
+  int height,
+  double pixelRatio = 1.0,
+}) async {
+  assert(key != null);
+  assert(pixelRatio != null && pixelRatio > 0);
+
+  final RenderRepaintBoundary wrappedWidget =
+      key.currentContext.findRenderObject();
+  ui.Image image = await wrappedWidget.toImage(pixelRatio: pixelRatio);
+
+  image = await _resize(image, width, height);
+
+  final ByteData byteData =
+      await image.toByteData(format: ui.ImageByteFormat.rawRgba);
+  final Uint8List imageData = byteData.buffer.asUint8List();
+  return PdfImage(document,
+      image: imageData, width: image.width, height: image.height);
+}
+
+Future<ui.Image> _resize(
+  ui.Image image,
+  int width,
+  int height,
+) async {
+  if (width == null && height == null) {
+    return image;
+  }
+
+  width ??= (height / image.height * image.width).toInt();
+  height ??= (width / image.width * image.height).toInt();
+
+  final Completer<ui.Image> ptr = Completer<ui.Image>();
+  final Uint8List data =
+      (await image.toByteData(format: ui.ImageByteFormat.rawRgba))
+          .buffer
+          .asUint8List();
+  ui.decodeImageFromPixels(
+    data,
+    image.width,
+    image.height,
+    ui.PixelFormat.rgba8888,
+    (ui.Image result) {
+      ptr.complete(result);
+    },
+    targetWidth: width,
+    targetHeight: height,
+  );
+  return ptr.future;
+}

@@ -4,7 +4,7 @@ description: Plugin that allows Flutter apps to generate and print documents to
 homepage: https://github.com/DavBfr/dart_pdf/tree/master/printing
 repository: https://github.com/DavBfr/dart_pdf
 issue_tracker: https://github.com/DavBfr/dart_pdf/issues
-version: 3.2.1
+version: 3.3.0
 
 environment:
   sdk: ">=2.3.0 <3.0.0"