小开

图像应该像下面这样作为附件嵌入到邮件中:

--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

HTML 部分引用图像如下:

<img src="cid:0123456789">

在一些客户机中，src = “ sig.png”也可以工作。

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

客户端也不应该屏蔽这个映像，因为它不是远程的。

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
c1AKgH8ETE1lBgo7O2JaU2UFAgRoDGoAXV4PD2qYagl7Vp0JDKenfwado0QCAQOQ
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AJ05At5msHPiCeSqLwUBzF6nVnXSuIwvTDYGsXPhiMmSRUOWAC436HmZU+yGDQYF
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E0CUAYETIKAjAifgWGMI2ehBgVtCeleGEkYmeUYGEQAAIfkECRQACwAsAAAAACgA
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oxgSCBSGwYDJMRgOhIGAupFGsVEG12JAmpHicaU3QDPe6fHjoSAQDlIBY6leDIUD
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2AkIAIAAAiiUKMGMICDRXQIn6IiCW4Qs4NYZTByppBkbRAAAIf4ZQm95J3MgSGFw
cHkgSG9saWRheXMgUGFnZQA7


--related_boundary--


--alternative_boundary--

您可以将其导入到 Sylpheed 或 Thunderbird (使用 Import/Export 工具扩展)或 Opera 的内置邮件客户端。然后，在 Opera 中，您可以切换“喜欢纯文本”来查看 HTML 和文本版本之间的差异。无论如何，您将看到 HTML 版本使用了签名中的嵌入图片。

小开

最佳答案

很重要

下面我的答案展示了如何使用数据 URI 嵌入图像。这对于网络是有用的，但是 将不能可靠地为大多数电子邮件客户端工作。用于电子邮件目的。

Base-64数据在 img标记中是合法的，我相信您的问题是如何正确地插入这样的图像标记。

可以使用在线工具或几行代码生成以64为基数的字符串。

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

小开

最近我遇到了同样的问题，在电子邮件中包括 QR 图像/png。QR 图像是一个字节数组，使用 ZXing 生成。我们不希望将其保存到文件中，因为从文件中保存/读取代价太高(速度太慢)。所以上面的两个答案对我来说都不起作用。下面是我解决这个问题的方法:

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");

假设 contentId 是“111122223333”，那么 HTML 部分应该包含以下内容:

<img src="cid: 111122223333">

不需要将字节数组转换为 Base64，因为 Commons Mail 会自动为您进行转换。希望这个能帮上忙。

base64 encoded images in email signatures

很重要