Retain class attribute of embedded svg element during conversion to img element

[MarcelBolten]

See #1404

[MarcelBolten]

@finwe is there anything else I can do to get this merged?
Guidance is very welcome.

[finwe]

This will not work with single quote in double quoted class string or vice versa, a backreference of the first quote is needed. It also will not work with unquoted class string.

[MarcelBolten]

I changed the regex (please see https://regex101.com/r/UK6HvN/3 for more details about the regex).
It will now only match the class attribute of the svg element and it can handle

1. single or double quoted class string
2. single quote in double quoted class string and vice versa
3. escaped double quote in double quoted class string
4. escaped single quote in single quoted class string and
5. unquoted class string

However, 3, 4, and 5 did not work for me

[php:error] PHP Fatal error:  Uncaught DivisionByZeroError: Division by zero in mpdf/mpdf/src/Tag/Img.php:372
Stack trace:
#0 mpdf/mpdf/src/Tag.php(240): Mpdf\\Tag\\Img->open()
#1 mpdf/mpdf/src/Mpdf.php(13771): Mpdf\\Tag->OpenTag()
Mpdf\\Mpdf->WriteHTML()

due to an issue not related to this PR and if I get it right unquoted class strings don't seem to be anticipated if I look at e.g. src/Image/Svg.php#L3131 but maybe (most likely) I miss something here.

function ImageSVG($data)
{
...
preg_match_all('/(<(linearGradient|radialgradient)[^>]*)xlink:href\s*=\s*["\']#(.*?)["\'](.*?)\/>/si', $data, $links);

[MarcelBolten]

Hi @finwe,
It has been some time since I made the requested changes. What do you think about the altered regex?
If the regex is to complicated a simpler approach could be to use a static class name like:

$html = str_replace($svgi[0][$i], '<img src="' . $file . '" class="mpdf-embedded-svg" />', $html);

[MarcelBolten]

Hi @finwe ,

Do you have some comment on this PR?