title: Image not showing in Flutter on pdf creation
body: <p>I have a problem where image from asset is not rendered in the screen when generating a pdf.</p>
  
  <p>I have pdf and printing package install. The printing package is used to load image from my image folder.</p>
  
  <p>Here is my code</p>
  
  <pre><code>final pdf = pw.Document(deflate: zlib.encode);
  
  writeOnPdf() async {
  
  const imageProvider = const AssetImage('images/sig1.png');
  
  final PdfImage sig1 = await pdfImageFromImageProvider(pdf: pdf.document, image: imageProvider);
  
  pdf.addPage(pw.Page(
    pageFormat: PdfPageFormat.a4,
    build: (pw.Context context) {
      return pw.Column(
        children: [
          pw.Row(
            mainAxisAlignment: pw.MainAxisAlignment.spaceBetween,
            children: [
              pw.Text("Dexandra Inventory", style: pw.TextStyle(fontSize: 28.0)),
              pw.Text("RECEIPT#1", style: pw.TextStyle(fontSize: 28.0))
            ]
          ),
          pw.SizedBox(
            height: 30.0
          ),
          pw.Row(
            mainAxisAlignment: pw.MainAxisAlignment.start,
            children: [
              pw.Text("Luqman +60186661360", style: pw.TextStyle(fontSize: 18.0)),
            ]
          ),
          pw.SizedBox(
              height: 30.0
          ),
          pw.Header(
            level: 0,
            child: pw.Text("1 Item (Qty:2)", style: pw.TextStyle(fontSize: 22.0))
          ),
          pw.SizedBox(
              height: 30.0
          ),
          pw.Row(
            mainAxisAlignment: pw.MainAxisAlignment.spaceEvenly,
            children: [
              pw.Text("2x", style: pw.TextStyle(fontSize: 16.0)),
              pw.Text("Air Feshener", style: pw.TextStyle(fontSize: 16.0)),
              pw.Text("RM 10.00", style: pw.TextStyle(fontSize: 16.0, color: PdfColors.grey)),
              pw.SizedBox(width: 40.0),
              pw.Text("RM 20.00", style: pw.TextStyle(fontSize: 16.0, fontBold: pw.Font.courierBold())),
            ]
          ),
          pw.SizedBox(
              height: 40.0
          ),
          pw.Row(
              mainAxisAlignment: pw.MainAxisAlignment.end,
              children: [
                pw.Column(
                  children: [
                    pw.Text("Total: RM 20.00", style: pw.TextStyle(fontSize: 20.0, fontBold: pw.Font.courierBold())),
                    pw.SizedBox(
                        height: 15.0
                    ),
                    pw.Text("Cash: RM 20.00", style: pw.TextStyle(fontSize: 16.0)),
                  ]
                ),
              ]
          ),
          pw.Header(
              level: 0,
              child: pw.Text("")
          ),
          pw.Row(
            mainAxisAlignment: pw.MainAxisAlignment.center,
            children: [
              pw.Text("March 30, 2020 4:41 PM", style: pw.TextStyle(fontSize: 16.0, color: PdfColors.grey)),
            ]
          ),
          pw.Row(
            mainAxisAlignment: pw.MainAxisAlignment.spaceAround,
            children: [
              pw.Image(sig1),
            ]
          )
        ]
      ); // Center
  }));
  }
  </code></pre>
  
  <p>Everything works fine until the last widget, which is the Image. It is not displayed in the PDF page.</p>
  
  <p>pubspec.yml</p>
  
  <pre><code>assets:
  - images/
  </code></pre>
  
  <p>And this is what appears in the terminal, when I click a button to generate pdf.
  Not sure if it has anything related to the image not being rendered.</p>
  
  <pre><code>I/flutter (13171): Helvetica has no Unicode support see https://github.com/DavBfr/dart_pdf/wiki/Fonts-Management
  E/AccessibilityBridge(13171): VirtualView node must not be the root node.
  E/AccessibilityBridge(13171): VirtualView node must not be the root node.
  I/chatty  (13171): uid=10341(com.example.dexandrainventory) identical 2 lines
  E/AccessibilityBridge(13171): VirtualView node must not be the root node.
  E/AccessibilityBridge(13171): VirtualView node must not be the root node.
  I/chatty  (13171): uid=10341(com.example.dexandrainventory) identical 5 lines
  </code></pre>