Value of BlipExtension Schema URI: "28A0092B-C50C-407e-A947-70E740481C1C"

Question

Question

The class DocumentFormat.OpenXml.Drawing.BlipExtension has a property called Uri. In numerous examples I've seen the value 28A0092B-C50C-407e-A947-70E740481C1C used; but never found what this value is / whether it's important, or if it's arbitrary and only prevalent because of people copy-pasting from existing sample code.

Does anyone know what the relevance of this GUID value is?

Background

I've been fixing a bug in a legacy application, and have been refactoring at the same time to remove some of the code's spaghettification.

Whilst doing this I spotted a few hardcoded values; any image inserted into the document is given the name Koala.jpg. The system has nothing to do with Koalas; implying that the person had simply copy-pasted some code and not thought about the context / meaning of these values. Another hardcoded value is the Uri for a BlipExtension: 28A0092B-C50C-407e-A947-70E740481C1C. I wanted to determine whether this GUID has any particular meaning, or if it's just a unique value. Googling shows this value used in lots of sample code, but so far I've found no explanation of what it is. Example results below.

• https://technet.microsoft.com/pl-PL/library/bb497430(v=office.14).aspx?cs-save-lang=1&cs-lang=vb (with Koala.jpg)
• https://msdn.microsoft.com/en-us/library/office/bb497430.aspx
• Insert an image into word document using open xml and C#

Looking at the BlipExtension documentation doesn't give much info on how I could find out what this GUID is / what schema this refers to. https://msdn.microsoft.com/en-us/library/documentformat.openxml.drawing.blipextension.uri(v=office.14).aspx

Answer 1

It looks like it's a specific value for the useLocalDpi extension.

The [MS-ODRAWXML]: Office Drawing Extensions to Office Open XML Structure document lists many extensions to the DrawingML spec, each with their own unique Guid Uri attribute.

Section 2.3.1.13 is the section that mentions 28A0092B-C50C-407e-A947-70E740481C1C as the Extension list URI attribute for the useLocalDpi extension. It looks like this setting was introduced in Word 2010 so an extension was added to support it.

As @Cindy Meister pointed out in the comments the Koala.jpg file is a sample picture that is provided with (many versions of) Windows.