Send Base64 Images in Email with Google Apps

[masoodkhoshgard]

Description

#19930

Gmail will not render base64 images embedded inside HTML emails but with Google Apps Script
on Gmail:

on personal mail server:

Checklist

• I fully tested it as developer / designer and created unit / integration tests

[codecov]

Codecov Report

Attention: Patch coverage is 5.47945% with 69 lines in your changes missing coverage. Please review.

Project coverage is 52.09%. Comparing base (5857f65) to head (58331fc).
Report is 158 commits behind head on dev.

❗ Current head 58331fc differs from pull request most recent head 089cc52

Please upload reports for the commit 089cc52 to get more accurate results.

Files	Patch %	Lines
....Abp.Emailing/Volo/Abp/Emailing/EmailSenderBase.cs	5.47%	69 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##              dev   #19932   +/-   ##
=======================================
  Coverage   52.09%   52.09%           
=======================================
  Files        3107     3105    -2     
  Lines       99366    99310   -56     
  Branches     7514     7515    +1     
=======================================
- Hits        51763    51738   -25     
+ Misses      46044    46016   -28     
+ Partials     1559     1556    -3     

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[maliming]

Thank you for your code.

The NormalizeMailAsync is designed to override and meet your cases.

We don't need to add the Gmail-relevant code to the framework.

[masoodkhoshgard]

Thank you for your code.

The NormalizeMailAsync is designed to override and meet your cases.

We don't need to add the Gmail-relevant code to the framework.

Thanks @maliming
But keep in mind that Gmail is a public service and this problem happens a lot and that it is likely to occur for other mail services as well.

[ebicoglu]

The regex you provided doesn't cover all variants of a base64 image element.
Here's a better regex that finds all possible src with the base64 format:

src\s*=\s*("|')\s*data\s*:\s*image/\s*(png|jpeg|gif);\s*base64,([^""]+)."|'

syntax:

bool foundMatch = false;
try {
	foundMatch = Regex.IsMatch("input-text-here...", @"src\s*=\s*(""|')\s*data\s*:\s*image/\s*(png|jpeg|gif);\s*base64,([^""""]+).""|'", RegexOptions.Singleline);
} catch (ArgumentException ex) {
	// Syntax error in the regular expression
}

[masoodkhoshgard]

@ebicoglu
I think it would be better to use the following regex pattern:

src\s*=\s*(""|')\s*data\s*:\s*(?<mediaType>[\w/\-\.]+);(?<encoding>\w+),(?<data>.*?)(""|')

Because it covers all tags that use base64, such as fonts, video, audio and more, not just limited to images.

[ebicoglu]

Is cid a universal HTML format? or only Gmail understand this tag?

[masoodkhoshgard]

No, "cid" is not a universal HTML format. CID stands for "Content-ID" and is used specifically in the context of email and HTML email messages.

In email, the "cid" is used to reference embedded content, such as images or other media, that is included within the email message itself. The CID acts as a unique identifier for that embedded content.

For example, in an HTML email, an image might be referenced using a CID like this:
<img src="cid:image001.jpg">

This tells the email client to look for an image with the content ID "image001.jpg" that is embedded within the email message.

However, this "cid" reference is not a standard HTML format that can be used outside of the email context. In regular web pages, images and other resources are typically referenced using standard URL paths, not CIDs.

So in summary, "cid" is specific to email and not a universal HTML format for referencing content on the web. Regular HTML uses other methods like [src="image.jpg"] to link to external resources.

[maliming]

I have formatted the code. The code differences are now simpler.

@ebicoglu You can review it again. Thanks.