Image from sharepoint - where to find image in documentFormat.openXml?

[evlo]

Is there an easy way to convert html that points to image on SharePoint?
I do not know what exact auth the sharepoint will use.

I tried test code like this as a way to get around using SharePoint image url, which in this case would most likely be possible

                    HtmlToOpenXml.HtmlConverter converter = new HtmlToOpenXml.HtmlConverter(mainPart);
                    converter.ParseHtml("<img src='data:image/png;base64,iVBORw0KG....=='></img>");
                    mainPart.Document.Save();

results in

<w:body xmlns:w="http://schemas.openxmlformats.org/wordprocessingml/2006/main"><w:p><w:r><w:drawing><wp:inline distT="0" distB="0" distL="0" distR="0" xmlns:wp="http://schemas.openxmlformats.org/drawingml/2006/wordprocessingDrawing"><wp:extent cx="4876800" cy="4876800" /><wp:effectExtent l="19050" t="0" r="0" b="0" /><wp:docPr id="2" name="Picture 2" descr="" /><wp:cNvGraphicFramePr><a:graphicFrameLocks noChangeAspect="1" xmlns:a="http://schemas.openxmlformats.org/drawingml/2006/main" /></wp:cNvGraphicFramePr><a:graphic xmlns:a="http://schemas.openxmlformats.org/drawingml/2006/main"><a:graphicData uri="http://schemas.openxmlformats.org/drawingml/2006/picture"><pic:pic xmlns:pic="http://schemas.openxmlformats.org/drawingml/2006/picture"><pic:nvPicPr><pic:cNvPr id="2" name="" descr="" /><pic:cNvPicPr><a:picLocks noChangeAspect="1" noChangeArrowheads="1" /></pic:cNvPicPr></pic:nvPicPr><pic:blipFill><a:blip r:embed="Re8ec0006bc874fdf" xmlns:r="http://schemas.openxmlformats.org/officeDocument/2006/relationships" /><a:srcRect /><a:stretch><a:fillRect /></a:stretch></pic:blipFill><pic:spPr bwMode="auto"><a:xfrm><a:off x="0" y="0" /><a:ext cx="4876800" cy="4876800" /></a:xfrm><a:prstGeom prst="rect"><a:avLst /></a:prstGeom></pic:spPr></pic:pic></a:graphicData></a:graphic></wp:inline></w:drawing></w:r></w:p></w:body>

so that is working.

As I'm doing some other stuff with the document and just taking InnerXML of the body, at least that is my plan for now - where can I find image attachment in the documentFormat.openXml WordprocessingDocument package?

I guess maybe better way to ask - what is the easiest way i can get /media/image.png from the zip stream and keep xml pointing to it in working in different openXml document?

[onizet]

You can implement your own version of IWebRequestor and provide it to the constructor of HtmlConverter.
There are so many authentication mode in SharePoint (on prem vs online) but by rolling out your own webRequestor class, you can control the SP ClientContext.