Dart
Build a multipart/related MIME Message

Demonstrates how to construct a multipart/related MIME message containing HTML and a related JPG image.
Chilkat Dart Downloads

Dart
import 'package:chilkat/chilkat.dart';

void main() {
  // This example requires the Chilkat API to have been previously unlocked.
  // See Global Unlock Sample for sample code.

  // Start with an empty MIME object...
  final mime = CkMime();

  // Initialize it as multipart/related.
  mime.newMultipartRelated();

  // Set a top-level MIME header field.
  mime.setHeaderField('Subject', 'Test HTML email with JPG image.');

  // Generate a Content-ID.  This will contain random data that will allow
  // the HTML's "img" tag to reference the image part in the MIME.
  final crypt = CkCrypt2();
  crypt.encodingMode = 'hex';

  final sbContentId = CkStringBuilder();
  sbContentId.append('part1.');
  sbContentId.append(crypt.genRandomBytesENC(4));
  sbContentId.append('.');
  sbContentId.append(crypt.genRandomBytesENC(4));
  sbContentId.append('@chilkatsoft.com');

  // Create the HTML body.
  final sbHtml = CkStringBuilder();
  sbHtml.append('<html><head>\r\n');
  sbHtml.append('<meta http-equiv="Content-Type" content="text/html; charset=utf-8">\r\n');
  sbHtml.append('  </head>\r\n');
  sbHtml.append('  <body bgcolor="#FFFFFF" text="#000000">\r\n');
  sbHtml.append('    <p>This is a test.&nbsp; <img src="cid:CONTENT_ID" height="20" width="20"></p>\r\n');
  sbHtml.append('  </body>\r\n');
  sbHtml.append('</html>\r\n');
  var numReplacements = sbHtml.replace('CONTENT_ID', sbContentId.getAsString());

  // Create the HTML MIME part.
  final htmlMime = CkMime();
  htmlMime.setBodyFromHtml(sbHtml.getAsString());
  htmlMime.encoding = '8bit';
  htmlMime.charset = 'utf-8';

  // Load our JPG image from a file.
  final fac = CkFileAccess();
  final jpgBytes = fac.readEntireFile('qa_data/jpg/starfish20.jpg');

  // Create an image/jpeg MIME part.
  final jpgMime = CkMime();
  jpgMime.setBodyFromBinary(jpgBytes);
  // Setting the following properties has the effect of adding
  // the Content-Type, Content-Transfer-Encoding, and Content-Disposition header fields.
  // These header fields could also be set via the SetHeaderField method, in which case
  // the values of the affected properties would be updated.
  jpgMime.contentType = 'image/jpeg';
  jpgMime.name = 'starfish20.jpg';
  jpgMime.encoding = 'base64';
  jpgMime.disposition = 'inline';
  jpgMime.filename = 'starfish20.jpg';

  final sbContentIdHdr = CkStringBuilder();
  sbContentIdHdr.append('<CONTENT_ID>');
  numReplacements = sbContentIdHdr.replace('CONTENT_ID', sbContentId.getAsString());
  jpgMime.setHeaderField('Content-ID', sbContentIdHdr.getAsString());

  // Add both parts as children of the multipart/related
  mime.appendPart(htmlMime);
  mime.appendPart(jpgMime);
  print(mime.getMime());

  // --------------------------------------------------------------
  // --------------------------------------------------------------
  // This example builds the following MIME message.  The boundary
  // and Content-ID strings contain random data and will be different.  

  // Content-Type: multipart/related; boundary="------------A940F1230E6F0105F03DB2CB"
  // Subject: Test HTML email with JPG image.
  // 
  // --------------A940F1230E6F0105F03DB2CB
  // Content-Type: text/html; charset="utf-8"
  // Content-Transfer-Encoding: 8bit
  // 
  // <html><head>
  // <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
  //   </head>
  //   <body bgcolor="#FFFFFF" text="#000000">
  //     <p>This is a test.&nbsp; <img src="cid:part1.E16AE3B4.1505C436@chilkatsoft.com" height="20" width="20"></p>
  //   </body>
  // </html>
  // 
  // --------------A940F1230E6F0105F03DB2CB
  // Content-Transfer-Encoding: base64
  // Content-Type: image/jpeg; name="starfish20.jpg"
  // Content-Disposition: inline; filename="starfish20.jpg"
  // Content-ID: <part1.E16AE3B4.1505C436@chilkatsoft.com>
  // 
  // /9j/4AAQSkZJRgABAQEASABIAAD//gAmRmlsZSB3cml0dGVuIGJ5IEFkb2JlIFBob3Rvc2hvcD8g
  // NC4w/9sAQwAQCwwODAoQDg0OEhEQExgoGhgWFhgxIyUdKDozPTw5Mzg3QEhcTkBEV0U3OFBtUVdf
  // YmdoZz5NcXlwZHhcZWdj/9sAQwEREhIYFRgvGhovY0I4QmNjY2NjY2NjY2NjY2NjY2NjY2NjY2Nj
  // Y2NjY2NjY2NjY2NjY2NjY2NjY2NjY2NjY2Nj/8IAEQgAFAAUAwERAAIRAQMRAf/EABcAAAMBAAAA
  // AAAAAAAAAAAAAAIDBAX/xAAYAQADAQEAAAAAAAAAAAAAAAABAgMEAP/aAAwDAQACEAMQAAAB2kZY
  // NNEijWKddfTmLgALWH//xAAbEAACAgMBAAAAAAAAAAAAAAABAgMRAAQSE//aAAgBAQABBQL0XqN+
  // pM2aqJGMiqFFCyg7z//EABwRAAICAgMAAAAAAAAAAAAAAAERAAIQIQMSUf/aAAgBAwEBPwHqU5aq
  // Axx+y1tMQl4elj//xAAcEQEAAQUBAQAAAAAAAAAAAAABEQACEBIhA1H/2gAIAQIBAT8B3Bhqy7Zc
  // enyiwmGgDhiOzj//xAAdEAABAwUBAAAAAAAAAAAAAAABAAIREBIhIkFR/9oACAEBAAY/ArZyn+Cg
  // xtxWuJaoCnqDuin/xAAcEAABBAMBAAAAAAAAAAAAAAABABEhYRAxQVH/2gAIAQEAAT8hkEwPUUR9
  // DYfE4nxtRpIkBTsayuALIiuY/9oADAMBAAIAAwAAABDWPTsf/8QAGhEAAwADAQAAAAAAAAAAAAAA
  // AAEREDFBIf/aAAgBAwEBPxC0DVPcWm+Ce4OesrkE6bjH/8QAGBEBAQEBAQAAAAAAAAAAAAAAAREA
  // QRD/2gAIAQIBAT8QahMiOc8YgSrnTY3ELclHXn//xAAcEAEBAAIDAQEAAAAAAAAAAAABEQAhMUFx
  // EFH/2gAIAQEAAT8Qn3igmSZSj+c4N4zapMy9IjFV98wncN2iuLFsCEbDGxQkI6RO/n//2Q==
  // 
  // --------------A940F1230E6F0105F03DB2CB--
  // 
}