Friday, December 15, 2006

Base64, MHTML, and IE

In HTML 4.0, binary objects (e.g. image) can be inlined with Base64 encoding. However, Internet Explorer totally ignores the standard. Even in IE7, base64 image is still not supported.

Two solutions proposed by Dean Edwards and Luiz Angelo De Luca are trying to solve the problem. Both of them are implemented in PHP. Base64Html is a Java implementation of Luiz Angelo De Luca's solution: convert the HTML into MHTML (HTML Mail format).

Luiz Angelo De Luca's solution can be genernalize to the following steps:
  1. Buffer the output and add a function callback
  2. If the browser is IE, set the HTTP header to MHTML
  3. Convert the HTML to MHTML
Luiz Angelo De Luca has implemented it in a single PHP. In Java, we make use of HttpServletResponseWrapper (for #1), Serlvet Filter (for #2), and Apache Jakarta Commons Email API (for MHTML construction). Source code and example web app are available at: