Convert Inline Data-URL Images to Related Parts

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Demonstrates the Chilkat Email.ConvertInlineImages method, which converts images embedded inline within HTML (as base64 data URLs) into multipart/related MIME parts referenced from the HTML by cid:. This example sets an HTML body containing a data-URL image and converts it.

Background: HTML can embed an image two ways: as a data: URL (the base64 bytes sit right in the src attribute) or as a related part referenced by cid:. Many email clients don't render data: URLs for security reasons, so converting them to proper multipart/related parts — the traditional email way to embed images — greatly improves how reliably the images display.

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bool success = false;

//  Demonstrates the ConvertInlineImages method, which converts images embedded inline within
//  HTML (as base64 data URLs) into multipart/related MIME parts referenced from the HTML by
//  CID.

Chilkat.Email email = new Chilkat.Email();
email.Subject = "Convert inline images";

//  An HTML body with a base64 data-URL image (a 1x1 PNG).
email.SetHtmlBody("<html><body><img src=\"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAQAAAC1HAwCAAAAC0lEQVR42mP8z8BQDwAEhQGAhKmMIQAAAABJRU5ErkJggg==\"/></body></html>");

Debug.WriteLine("NumRelatedItems before = " + Convert.ToString(email.NumRelatedItems));

//  Convert the inline data-URL image(s) to multipart/related parts referenced by CID.

success = email.ConvertInlineImages();
if (success == false) {
    Debug.WriteLine(email.LastErrorText);
    return;
}

Debug.WriteLine("NumRelatedItems after = " + Convert.ToString(email.NumRelatedItems));