OpenXML - Get Image Alt Text Title

Question

I am attempting to iterate through the images in a PowerPoint presentation using OpenXML.

I have worked out how to do that.

I am now attempting to get the Images Alt-Text Title....

Here is my code:

List<ImagePart> imageParts = new List<ImagePart>();

part.GetPartsOfType<ImagePart>(imageParts);

foreach (ImagePart imagePart in imageParts)
{
    if (imagePart != null)
    {

    // Get the Relationship Id
    string oldRelID = part.GetIdOfPart(imagePart);

    // Get the Alt-Text Tile relating to this image

    }
}

Any OpenXML experts out there that could give me some pointers?

Thanks

UPDATE:

I have tried iterating through the XML but when there are multiple images on the slide I am getting the incorrect value for title for the relating image.

I think I need to be able to use the ImagePart Id to then find the corresponding title

The code below gets the titles out of order...

foreach (ImagePart imagePart in imageParts)
{
    string mapReference = "";

    XmlNode thisNode = pictureNodeList[imageCounter];

    foreach (XmlNode xmlnode in thisNode)
    {
        foreach (XmlNode xmlchildnode in xmlnode)
        {
            foreach (XmlAttribute att in xmlchildnode.Attributes)
            {
                if (att.Name == "title")
                {
                    mapReference = att.Value;
                    imageCounter += 1;
                 }
            }
         }
    }
}

Haihaida

Here' how I find such things out: Create a document with what you want (an image with an alt text) then look for it in the XML files. This should give you anough information to figure out how to access the desired information. – Weiner

Answer 1

You're 90% of the way there.

You need to find the Blip element whose Embed property matches the Id of the ImagePart you have. The Blip is contained within a BlipFill which in turn is contained within a Picture element. The Picture (pic in the XML) element has a NonVisualPictureDrawingProperties element (nvPicPr) which in turn has a NonVisualDrawingProperties element (cNvPr) and it's in there where you'll find the title. For example your XML could look like this:

<p:pic>
    <p:nvPicPr>
       <p:cNvPr id="4" name="Picture 3" descr="My Description" title="My Title" />
       <p:cNvPicPr>
          <a:picLocks noChangeAspect="1" />
       </p:cNvPicPr>
       <p:nvPr />
    </p:nvPicPr>
    <p:blipFill>
       <a:blip r:embed="rId2" cstate="print">
          <a:extLst>
             <a:ext uri="{28A0092B-C50C-407E-A947-70E740481C1C}">
                <a14:useLocalDpi xmlns:a14="http://schemas.microsoft.com/office/drawing/2010/main" val="0" />
             </a:ext>
          </a:extLst>
       </a:blip>
       <a:stretch>
          <a:fillRect />
       </a:stretch>
    </p:blipFill>
    <p:spPr>
       <a:xfrm>
          <a:off x="7260298" y="5445224" />
          <a:ext cx="1883701" cy="1412776" />
       </a:xfrm>
       <a:prstGeom prst="rect">
          <a:avLst />
       </a:prstGeom>
    </p:spPr>
 </p:pic>

The following code will output the Title property of each image. Note that as you have a strongly typed Picture object you can get to the other properties easily too (such as Description for example).

using (PresentationDocument doc =
            PresentationDocument.Open(filename, false))
{
    //get the first slide
    SlidePart part = doc.PresentationPart.SlideParts.First();

    //get all ImageParts in the first slide
    List<ImagePart> imageParts = new List<ImagePart>();
    part.GetPartsOfType<ImagePart>(imageParts);

    foreach (ImagePart imagePart in imageParts)
    {
        //find the picture related to the image
        Picture pic = part.Slide.Descendants<Picture>().Where(p => 
                        p.BlipFill.Blip.Embed == part.GetIdOfPart(imagePart)).FirstOrDefault();

        //Output the Title property
        Console.WriteLine(pic.NonVisualPictureProperties.NonVisualDrawingProperties.Title);
    }
}

Frangipane