Auto Update every picture in a PowerPoint Slideshow - vba

Question

I have a very large and complex PowerPoint with a full size image as the background for every individual slide. I have a directory full of these background pictures, which are all JPEG's. Sometimes I change these photographs, which are made with Photoshop, and when I change them, I save them over the original JPEG in the same directory.
I then have to update them in the PowerPoint. The manual functios to do this is to right-click the photograph, and click replace photo, then pick the new JPEG from the file menu. I want to write a macro in Visual Basic that will go through the entire slideshow, and reload the graphic from the updated JPEGs, without me having to do it manually. I don't know if it is possible, because I don't know if PowerPoint actually remembers the path and filename of each picture that it places.
Is there a picture property which contains the path and filename that was used to paste the picture in the first place? If there is, I could find that property, query it, and use that as the path to reload and thereby update the picture recursively all the way through slide by slide.
Would this be possible?

Answer 1

Is there a picture property which contains the path and filename that was used to paste the picture in the first place?
Not that I'm aware of, but you can create your own, using the Tags property:
http://msdn.microsoft.com/en-us/library/office/ff744290(v=office.15).aspx
You will have to assign a custom tag for each slide, like:
Sub AssignTag()
Dim sld as Slide
Set sld = ActivePresentation.Slides(1)
sld.Tags.Add "img_location", "C:\files\image1.JPG"
End Sub
Once the slide's Tags have been configured, then you can do something like this to update from that location:
Sub UpdateJPGs()
Dim sld As Slide
Dim path As String
For Each sld In ActivePresentation.Slides
path = sld.Tags("img_location")
If Not path = vbNullString Then
On Error Resume Next
sld.Background.Fill.UserPicture path
If Err Then
MsgBox "Unable to update slide #" & sld.SlideNumber
Err.Clear
End If
On Error GoTo 0
End If
Next
End Sub