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base64 encoded images in email signatures

I have to include some images (company logo's etc) in email signatures. I've had all sorts of issues using the embedded images produced by the email system in question (they get sent as attachments generally) and as linked images (requiring permission to display them in the email received).

I have just seen some email from exchange that has a base64 image representation of the logo and uses a tag to do the displaying. I'm looking for some information on how I could do this in an email signature if possible (how do I generate the base64 version of the logo for a start and what code do I need to get it to work)?

I've tried simple things such as

<body> <span> <img src=.... > </span> </body> 

but all I get is the alt text so I'm obviously doing something wrong here.

like image 940
Peter Nunn Avatar asked Feb 02 '12 09:02

Peter Nunn


2 Answers

The image should be embedded in the message as an attachment like this:

--boundary Content-Type: image/png; name="sig.png" Content-Disposition: inline; filename="sig.png" Content-Transfer-Encoding: base64 Content-ID: <0123456789> Content-Location: sig.png  base64 data  --boundary 

And, the HTML part would reference the image like this:

<img src="cid:0123456789"> 

In some clients, src="sig.png" will work too.

You'd basically have a multipart/mixed, multipart/alternative, multipart/related message where the image attachment is in the related part.

Clients shouldn't block this image either as it isn't remote.

Or, here's a multipart/alternative, multipart/related example as an mbox file (save as windows newline format and put a blank line at the end. And, use no extension or the .mbs extension):

From  From: [email protected] To: [email protected] Subject: HTML Messages with Embedded Pic in Signature MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="alternative_boundary"  This is a message with multiple parts in MIME format.  --alternative_boundary Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit  test  --  [Picture of a Christmas Tree]  --alternative_boundary Content-Type: multipart/related; boundary="related_boundary"  --related_boundary Content-Type: text/html; charset="utf-8" Content-Transfer-Encoding: 8bit  <!DOCTYPE html> <html>     <head>         <meta charset="utf-8">         <title></title>     </head>     <body>         <p>test</p>         <p class="sig">-- <br><img src="cid:0123456789"></p>     </body> </html>  --related_boundary Content-Type: image/png; name="sig.png" Content-Disposition: inline; filename="sig.png" Content-Location: sig.png Content-ID: <0123456789> Content-Transfer-Encoding: base64  R0lGODlhKAA8AIMLAAD//wAhAABKAABrAACUAAC1AADeAAD/AGsAAP8zM///AP// ///M//////+ZAMwAACH/C05FVFNDQVBFMi4wAwGgDwAh+QQJFAALACwAAAAAKAA8 AAME+3DJSWt1Nuu9Mf+g5IzK6IXopaxn6orlKy/jMc6vQRy4GySABK+HAiaIoQdg uUSCBAKAYTBwbgyGA2AgsGqo0wMh7K0YEuj0sUxRoAfqB1vycBN21Ki8vOofBndR c1AKgH8ETE1lBgo7O2JaU2UFAgRoDGoAXV4PD2qYagl7Vp0JDKenfwado0QCAQOQ DIcDBgIFVgYBAlOxswR5r1VIUbCHwH8HlQWFRLYABVOWamACCkiJAAehaX0rPZ1B oQSg3Z04AuFqB2IMd+atLwUBtpAHqKdUtbwGM1BTOgA5YhBr374ZAxhAqRVLzA53 OwTEAjhDIZYs09aBASYq+94HfAq3cRt57sWDct2EvEsTpBMVF6sYeEpDQIFDdo62 BHwZApjEhjW94RyQTWK/FPx+Ahpg09GdOzoJ/ESx0JaOQ42e2tsiEYpCEFwAGi04 8g6gSgNOovD0gBeVjCPR2BIAkgOrmSNxPo3rbhgHZiMFPnLkBg2BAuQ2XdmlwK1Z ooZu1sRz6xWlxd4U9GIHwOmdzFgCFKCERYNoeo2BZsPp0KY+A/OAfZDYWKJZLZBo 1mQXdlojvxNYiXrD8I+2uEvTdFJQksID0XjXiUwjJm6CzBVeBQgwBop1ZPpC8RKt YN5RCpS6XiyMht093o8KcFFf/vKE0dCmaLeWYhQMwbeQaHLRfNk9o5Q13lQGklFQ aMLFRLcwcN5qSWmGxS2jKQQFL9nEAgxsDEiwlAHaPPJWIfroo6FVEun0VkL4UABA CAjUiIAFM2YQogzcoLCjC3HNsYB1aSBB5JFrZBABACH5BAkUAAsALAAAAAAoADwA AwT7cMlJa3U2670x/6DkjKQXnleJrqnJruMxvq8xHDQbJEyC5yheAnh6MI5HYkgg YNgGSo7BcGAMBNHNYGA7ELpZiyFBLg/DFvLArEBPHoAEgXDYChQP90IAoNYJCoGB aACFhX8HBwoGegYAdHReijZoBXxmPWRYYQ8PZmSZZHmcnqBITp2jSgIBN5BVBFwC BVkGAQJPiVV2rFCrCq1/sXUHAgQFAL45BncFNgSfW8wASoKBB59lhoVAnQqfDNCf AJ05At5msHPiCeSqLwUBzF6nVnXSuIwvTDYGsXPhiMmSRUOWAC436HmZU+yGDQYF 81FhV+aevzUM3oHoZBD7W7Zs9VaUIhOn4pwE38p0srLCQCqSciBFUuBFGgEryj7E Ojhg2yOG1hQMIMCEy4p8PB8llKmAIReiW040keUvmUygiexcwbWJwxUrzBDW+Thn qLEB5UDUe0LxYwJmAhKk+pAqVLZE69qWGZpTQwG7ZISuw7uwzDFAXTXYYoJraKym Q/HSASDpiiUFljbYitfYRtCF635yMRBUn4UA8aYclCw0shefW7gUgPxBKGPHA5pK MpwsKy5AcmNZSIVHjdjI2eLwVZlK44IHQT8lkq7XTDznrAIEWMTErZwbsT/hQj1L noXLV6YwS5eIJqIDf4tyLZB5Av1ZNrLzQSplrXVkOgxItBU1E+DCwC2xFZUME5dZ c5AB9aw2jXkSQLhFIrj4xAx9szGWzwABdkGATwuAeEokW4wY24oK8MMViAjxxcc8 E0CUAYETIKAjAifgWGMI2ehBgVtCeleGEkYmeUYGEQAAIfkECRQACwAsAAAAACgA PAADBPtwyUlrdTbrvTH/oOSMpBeeV4muqcmu4zG+r6EcNBskSoLnJ4VQCAw9ErzE oxgSCBSGwYDJMRgOhIGAupFGsVEG12JAmpHicaU3QDPe6fHjoSAQDlIBY6leDIUD dnp9C04DdXh3eAaEUTeKdwJRagUCBGdnW3JHmJh8XHNmWAeLDwCfRQIBA6MMiQMG AgBcBgGSUgeuWQMAvb1MAgWruXAMrJYAUkU2wVGXDGZeAIxMCgVfaJhOVkB/PWeX nXM5AnScSKR2dmZzqCwFUAKjo1l4XpLULNuwWXYHAHgWCYD15AXBgV+wEACg7sDA A45oaLFy5ZKvXvYMEPCGYvvOwQOYAHRCQufFuU7/wp2Zo2AKCgPtwN3xR8/LLpcg kg1khaVlQyw8GRAwlC8nvp2HeM5UR8CYxp05L8ay8YcplmLGtmniwCtKLFhJR9oR amnAuBAiH9wK9G1kAgaxBCg5u6HdSUzp1LlNCqJAgZGBaC41Q6DAUAUfajm5ZUdK v7z08ATjmKGWAltecaVTqE5oFisB/EIpSiH06IcKpQTa3JSVagPCWm7wZsgOwJkg 3xaTrJFkFgvtFHDywmt1J2iB2pC0C9x0yItnsLx1K8xdoQDYCcQ9I5KwaynaalUS RnpBpYH4YiXoTipgIlIFtLSUFKwSBb/NtGCnb2Zl51fHo8hnhRZbSfCEKkgZkkcw TgBgyVdxeQNRMNNMoMBOpBxFUSx+ObgYPgS1BBRss/jxxzwAqsbLRfwh1VJyF5WI 2AkIAIAAAiiUKMGMICDRXQIn6IiCW4Qs4NYZTByppBkbRAAAIf4ZQm95J3MgSGFw cHkgSG9saWRheXMgUGFnZQA7  --related_boundary--  --alternative_boundary-- 

You can import that into Sylpheed or Thunderbird (with the Import/Export tools extension) or Opera's built-in mail client. Then, in Opera for example, you can toggle "prefer plain text" to see the difference between the HTML and text version. Anyway, you'll see the HTML version makes use of the embedded pic in the sig.

like image 81
Shadow2531 Avatar answered Oct 10 '22 19:10

Shadow2531


Important

My answer below shows how to embed images using data URIs. This is useful for the web, but will not work reliably for most email clients. For email purposes be sure to read Shadow2531's answer.


Base-64 data is legal in an img tag and I believe your question is how to properly insert such an image tag.

You can use an online tool or a few lines of code to generate the base 64 string.

The syntax to source the image from inline data is:

<img src="data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUA AAAFCAYAAACNbyblAAAAHElEQVQI12P4//8/w38GIAXDIBKE0DHxgljNBAAO 9TXL0Y4OHwAAAABJRU5ErkJggg==" alt="Red dot"> 

http://en.wikipedia.org/wiki/Data_URI_scheme

like image 40
Tim M. Avatar answered Oct 10 '22 19:10

Tim M.