I had exactly this problem a couple of months ago while working on a WYSIWYG email editor for my company. Outlook only supports background images if they're applied to the <body>
tag - any other element and it'll fail.
In the end, the only workaround I found was to use <div>
element for text input, then during the content submission process I fired an AJAX request with the <div>
's content to a PHP script which wrote the text onto a blank version of our header image, saved the file and returned its (uniquely generated) name. I then used Javascript to remove the <div>
and add an <img>
tag using the returned filename in the src
attribute.
You can get all the info/methodology from the imagecreatefrompng()
page on the PHP Docs site.