Add more image loading functions

@@ -14,6 +14,7 @@
 - Improve image buffer management
 - Optimize memory footprint
 - Add an exception if a jpeg image is not a supported format
+- Add more image loading functions
 
 ## 1.5.0
 

@@ -49,15 +49,13 @@ pdf.addPage(pw.Page(
       })); // Page
 ```
 
-To load an image it is possible to use the dart library [image](https://pub.dev/packages/image):
+To load an image from a file:
 
 ```dart
-final img = decodeImage(File('test.webp').readAsBytesSync());
-final image = PdfImage(
+final img = decodeImage();
+final image = PdfImage.file(
   pdf.document,
-  image: img.data.buffer.asUint8List(),
-  width: img.width,
-  height: img.height,
+  bytes: File('test.webp').readAsBytesSync(),
 );
 
 pdf.addPage(pw.Page(

@@ -22,6 +22,7 @@ import 'dart:math' as math;
 import 'dart:typed_data';
 
 import 'package:crypto/crypto.dart';
+import 'package:image/image.dart' as im;
 import 'package:meta/meta.dart';
 import 'package:utf/utf.dart';
 import 'package:vector_math/vector_math_64.dart';

@@ -41,6 +41,8 @@ class PdfImage extends PdfXObject {
     bool alpha = true,
     PdfImageOrientation orientation = PdfImageOrientation.topLeft,
   }) {
+    assert(image != null);
+
     final PdfImage im = PdfImage._(
       pdfDocument,
       width,
@@ -107,6 +109,42 @@ class PdfImage extends PdfXObject {
     return im;
   }
 
+  factory PdfImage.fromImage(
+    PdfDocument pdfDocument, {
+    @required im.Image image,
+    PdfImageOrientation orientation = PdfImageOrientation.topLeft,
+  }) {
+    assert(image != null);
+
+    return PdfImage(
+      pdfDocument,
+      image: image.getBytes(format: im.Format.rgba),
+      width: image.width,
+      height: image.height,
+      alpha: image.channels == im.Channels.rgba,
+      orientation: orientation,
+    );
+  }
+
+  factory PdfImage.file(
+    PdfDocument pdfDocument, {
+    @required Uint8List bytes,
+    PdfImageOrientation orientation = PdfImageOrientation.topLeft,
+  }) {
+    assert(bytes != null);
+
+    if (im.JpegDecoder().isValidFile(bytes)) {
+      return PdfImage.jpeg(pdfDocument, image: bytes);
+    }
+
+    final im.Image image = im.decodeImage(bytes);
+    return PdfImage.fromImage(
+      pdfDocument,
+      image: image,
+      orientation: orientation,
+    );
+  }
+
   factory PdfImage._alpha(
     PdfDocument pdfDocument,
     Uint8List image,

@@ -17,6 +17,7 @@ dependencies:
   archive: ^2.0.10
   qr: ^1.2.0
   barcode: ^1.5.0
+  image: ^2.1.4
 
 dev_dependencies:
   test:

@@ -84,6 +84,34 @@ void main() {
     );
   });
 
+  test('Pdf Image decode', () {
+    final Iterable<Widget> imageWidgets = imageFiles.map<Widget>(
+      (String image) => SizedBox(
+        child: Image(
+          PdfImage.file(
+            pdf.document,
+            bytes: gzip.decode(base64.decode(image)),
+          ),
+        ),
+        width: 200,
+        height: 200,
+      ),
+    );
+
+    pdf.addPage(
+      Page(
+        build: (Context context) => Center(
+          child: Wrap(
+            spacing: 20,
+            runSpacing: 20,
+            alignment: WrapAlignment.spaceEvenly,
+            children: imageWidgets.toList(),
+          ),
+        ),
+      ),
+    );
+  });
+
   tearDownAll(() {
     final File file = File('jpeg.pdf');
     file.writeAsBytesSync(pdf.save());
@@ -110,3 +138,9 @@ const List<String> images = <String>[
   '/9j/4AAQSkZJRgABAQEA3ADcAAD/4QAiRXhpZgAASUkqAAgAAAABABIBAwABAAAABwAAAAAAAAD/2wBDAAYEBQYFBAYGBQYHBwYIChAKCgkJChQODwwQFxQYGBcUFhYaHSUfGhsjHBYWICwgIyYnKSopGR8tMC0oMCUoKSj/2wBDAQcHBwoIChMKChMoGhYaKCgoKCgoKCgoKCgoKCgoKCgoKCgoKCgoKCgoKCgoKCgoKCgoKCgoKCgoKCgoKCgoKCj/wAARCAAwAFADASIAAhEBAxEB/8QAFgABAQEAAAAAAAAAAAAAAAAAAAkI/8QAFBABAAAAAAAAAAAAAAAAAAAAAP/EABQBAQAAAAAAAAAAAAAAAAAAAAD/xAAUEQEAAAAAAAAAAAAAAAAAAAAA/9oADAMBAAIRAxEAPwDVIAAAAAAAJVgAqoAAACVYAKqAAlWAAAAAAAAAAAD/2Q==',
   '/9j/4AAQSkZJRgABAQEA3ADcAAD/4QAiRXhpZgAASUkqAAgAAAABABIBAwABAAAACAAAAAAAAAD/2wBDAAYEBQYFBAYGBQYHBwYIChAKCgkJChQODwwQFxQYGBcUFhYaHSUfGhsjHBYWICwgIyYnKSopGR8tMC0oMCUoKSj/2wBDAQcHBwoIChMKChMoGhYaKCgoKCgoKCgoKCgoKCgoKCgoKCgoKCgoKCgoKCgoKCgoKCgoKCgoKCgoKCgoKCgoKCj/wAARCAAwAFADASIAAhEBAxEB/8QAFgABAQEAAAAAAAAAAAAAAAAAAAkI/8QAFBABAAAAAAAAAAAAAAAAAAAAAP/EABQBAQAAAAAAAAAAAAAAAAAAAAD/xAAUEQEAAAAAAAAAAAAAAAAAAAAA/9oADAMBAAIRAxEAPwDKgAAAAAAAAAKqAAAAlWACqgAJVgAqoAAAAAAACVYAP//Z',
 ];
+
+const List<String> imageFiles = <String>[
+  'H4sIAKx0cl4AA/t/4/8DBgEvN083BkZGRgYPIGT4f5vBmeE/pQBoCCPFhhxgEORgUGQwYmZUYmASZGQWZPx/hEEM7FQUwMgEFBcVQBdmEAQJY6hmAJkiIoguyvD/FgMPMyPQImZBBnuGVU0LGLS1GpoaVqiyCi1lm8gY4iDK4MAYwMDA/v8mAIKohPQ4AQAA',
+  'H4sIAAV2cl4AA+sM8HPn5ZLiYmBg4PX0cAkC0kZArMjBBCRF5PMvAylTTxfHkIjDb88ZMjIYcDAoxP5XM9vcsvrBS0bOEy+7quPmLFmKDrZ+Yjx0ienafeXk7UADGDxd/VzWOSU0AQCMWbgebgAAAA==',
+  'H4sIAFZ2cl4AA3P3dLMwTzRiUGRoYGDIXCUJRDoMQAASYWBSb+lfefot/+I5W251b7635zd/2yOPac86l706te0d9/FPPte/9T7/de41K4M1ANAWLyFIAAAA'
+];