Specifying alpha channel in css color via hex causes result color to be black

[nitz]

Description

If a CSS color is specified using a hex string that includes the alpha channel, the resulting color is black regardless of value. Specifying the alpha channel another way (e.g.: via rgb()) seems to work as expected though.

Example data

Reproduction example. (via LINQPad)

void Main()
{
	string template = 
"""
<svg viewBox="0 0 192 64" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
  <style type="text/css">
    text {{
      fill: {0};
    }}
    rect {{
      fill: #ffffff;
    }}
  </style>
  <rect width="100%" height="100%" />
  <text x="32" y="32" class="name">{1}</text>
</svg>
""";

	var svgs = new string[] {
		string.Format(template, "rgb(255, 0, 0, 255)", "Rgb red w/ alpha"),
		string.Format(template, "rgb(255, 0, 0, 128)", "Rgb red w/ alpha 128"),
		string.Format(template, "rgb(255, 0, 0)", "Rgb red w/ *no* alpha"),
		string.Format(template, "#ff0000ff", "Hex red w/ alpha 0xFF"),
		string.Format(template, "#ff000080", "Hex red w/ alpha 0x80"),
		string.Format(template, "#ff0000", "Hex red w/ *no* alpha"),
	};

	foreach (var svg in svgs)
	{
		var svgDoc = SvgDocument.FromSvg<SvgDocument>(svg);
		var bitmap = svgDoc.Draw();
		bitmap.Dump();
	}
}

Output result:

Used Versions

Svg v3.4.4 (Nuget)
.NET v7.0.5 (Roslyn v4.6.0-3.23259.8)
OS Windows 10 Pro For Workstations 22H2 19045.3086