base64 encoded images in email signatures

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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 (th

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星月不相逢

2020-11-22 16:37
Recently I had the same problem to include QR image/png in email. The QR image is a byte array which is generated using ZXing. We do not want to save it to a file because saving/reading from a file is too expensive (slow). So both of the answers above do not work for me. Here's what I did to solve this problem:
```
import javax.mail.util.ByteArrayDataSource;
import org.apache.commons.mail.ImageHtmlEmail;
...
ImageHtmlEmail email = new ImageHtmlEmail();
byte[] qrImageBytes = createQRCode(); // get your image byte array
ByteArrayDataSource qrImageDataSource = new ByteArrayDataSource(qrImageBytes, "image/png");
String contentId = email.embed(qrImageDataSource, "QR Image");
```
Let's say the contentId is "111122223333", then your HTML part should have this:

<img src="cid: 111122223333">

There's no need to convert the byte array to Base64 because Commons Mail does the conversion for you automatically. Hope this helps.
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不知归路

2020-11-22 16:40

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: from@example.com
To: to@example.com
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
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E0CUAYETIKAjAifgWGMI2ehBgVtCeleGEkYmeUYGEQAAIfkECRQACwAsAAAAACgA
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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.

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刺人心

2020-11-22 16:49
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
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base64 encoded images in email signatures

Important