Maintain original image size when moving images in open xml

When inserting images into content control boxes using openxml, the image dimensions will not change to those of the image, you will need to manually do this.

Which objects?

There are two places where the image size needs to be set, inside the DocumentFormat.OpenXml.Drawing.Pictures.Picture object and the DocumentFormat.OpenXml.Drawing.Wordprocessing.Inline object. Both of these objects contain an DocumentFormat.OpenXml.Drawing.Wordprocessing.Extent object which contains the Cx and Cy values for the image.

What size?

Now the next problem is knowing what the Cx and Cy values should be set to. Use the System.Drawing.Image object to get the Width and Height properties from your image. However, word image dimensions are not stored in pixels, they are stored in points.

Converting pixels to points can be very complicated when you're working with text but luckily with images there is a constant value we can use to calculate the points from a pixel value, which is 9525.

Code example please?

Moving images in word headers using OpenXML

From what I discovered moving images from one header in a document to another seems to be a huge problem for most people so I decided to try do this myself. I'm not 100% sure what other issues it might cause but I when I run the "Validate" command in the OpenXML Productivity Tools I get no errors and the images I'm moving are displaying correctly so for now I'm giving it the go ahead :)


Background


To move data from one document to another you can use altChunk but this does not copy headers and footers. If this doesn't phase you - you can read more about altChunk on Brian Jones blog: entry: http://blogs.msdn.com/b/brian_jones/archive/2008/12/08/the-easy-way-to-assemble-multiple-word-documents.aspx.


Brian Jones has tons of examples of how to manipulate documents. He also has some nice information about some open source code called "DocumentBuilder" which I stumbled upon but when I run the "Validate" command using the OpenXML Productivity Tools I get an error for each document I tried to merge so I decided this was not a good option for me. If you are interested though check it out here:  http://www.pubsub.com/events/5e5f8d3fd2346a54739b8b6bb0438b82


Another way to move elements from one part of a document to another is to actually use the "FeedData" method and pass in the other element by getting its Stream. This however doesn't work when moving images in headers between documents.

Looking Deeper

Create a blank document and insert any image into it's header. Use the OpenXML Productivity Tool to open the document and expand it's /word/document.xml node. You will see that there are few header xml nodes inside the document xml node. Thats because there are 3 types of headers inside a document or none at all. The three types distuinguish between First, Default and Even.


If you go to expand "w:document", "w:body" you will see "w:sectPr". If you reflect this node you will see the references to your headers. In my document my "Default" header has been referenced using id "rId8". If you reflect your "/word/document.xml node you should see which Header has been assigned "rId8". This helped me to find out which HeaderPart I need to retrieve to find the elements I'm looking for.


Start Coding


A HeaderPart can contain a few things but if I just have a plain header with an image it should contain a "/word/media/image1.png" element as well as a "w:hdr" element. What I did was create a new Header by passing the old headers OuterXML into the constructor and manually copy paste the Images seperately and this worked. Here is some example code:


reportImagePart.FeedData(headerImagePart.GetStream());

private static void ReplaceImages(HeaderPart headerPart, HeaderPart reportHeaderPart) 
{ 
  foreach (IdPartPair partPair in headerPart.Parts)   
  {
    OpenXmlPart openXmlPart = partPair.OpenXmlPart;   
    Type type = openXmlPart.GetType();   
    if (type.Name == "ImagePart")     
    {
      ImagePart headerImagePart = (ImagePart)openXmlPart;     
      string idImage = headerPart.GetIdOfPart(openXmlPart);     
      ImagePart reportImagePart = reportPart.AddNewPart<ImagePart>("image/png", idImage);
      Header headerNew = new Header(headerPart.Header.OuterXml);
    }
  }
}

This could probably be coded better but I'm still in the POC process. If anyone is having any issues with this strategy please let me know!!!