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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.

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

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JohnLBevan
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    1. MSDN appears to be down so I couldn't read up on the BlipExtension class. I can, however, tell you what Koala.jpg is: it's the file name of one of the Sample pictures provided with Windows. So it makes sense that you'd see this in a sample document. – Cindy Meister Nov 04 '15 at 12:57
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    2. For more information about BlipExtension I recommend the ECMA documentation for the Office Open XML spec. That goes into great detail. It can be downloaded for free from the ECMA site. For more clarification you can try asking in the MSDN forum for Open specifications (includes binary and other file formats). The Microsoft engineers (and not "contingent staff") monitor that forum. Unfortunately I'm travelling currently so can't give you a link... – Cindy Meister Nov 04 '15 at 12:57
  • Thanks @CindyMeister. Looking through the documentation now... http://www.ecma-international.org/publications/standards/Ecma-376.htm – JohnLBevan Nov 04 '15 at 13:17
  • Sadly no luck checking the spec (searching for the GUID). I've now asked here also: https://social.msdn.microsoft.com/Forums/en-US/056472c8-31cd-42e1-b527-5921aef16a24/value-of-blipextension-schema-uri-28a0092bc50c407ea94770e740481c1c?forum=os_binaryfile – JohnLBevan Nov 04 '15 at 14:16

1 Answers1

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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.

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petelids
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